Exhaled breath analysis technology enables the preliminary diagnosis of certain diseases via detecting the concentration of volatile organic compounds (VOCs) in human breath. Some studies indicate that acetone can serve as a biomarker to assist in the diagnosis of diabetes. Developing acetone gas sensors with low detection limits and high selectivity is thus crucial for achieving early screening of diabetes. In recent years, spinel ferrites, as an important class of metal oxides, have attracted much attention in the gas sensing field due to their low cost and excellent stability. Among them, ZnFe₂O₄ can improve the number of active sites on the material surface via tailoring its microstructure, thereby exhibiting a high sensitivity to VOCs like acetone. However, single-component ZnFe₂O₄ gas sensors suffer from issues such as high operating temperatures and low gas-sensing selectivity in practical detection. The existing research shows that ion doping is a modification method that induces lattice distortion in metal oxides, thereby regulating surface defects on the material. The generation of surface defects can provide more active centers for gas-sensing reactions and promote the adsorption of oxygen molecules on the material surface, thus improving its gas-sensing properties. Furthermore, doping rare-earth elements into MOS materials can enhance their catalytic activity and increase electron migration rates, leading to an improved sensing performance. This study was to prepare a series of La³⁺-doped ZnFe₂O₄ composites via electrospinning. Their morphology, surface chemical composition, and elemental valence states were characterized, and the gas-sensing properties of the composites were analyzed.

0.808 g Fe(NO₃)₃·9H₂O (AR, Sinopharm Chemical Reagent Co., Ltd., China), 0.297 g Zn(NO₃)₂·6H₂O (AR, Sinopharm Chemical Reagent Co., Ltd., China), and varying mass ratios of La(NO₃)₃·nH₂O (AR, Sinopharm Chemical Reagent Co., Ltd., China) were accurately weighed. Each mixture was put into respective 10 mL beakers, add 5 mL of DMF (AR, Sinopharm Chemical Reagent Co., Ltd., China), and stir to dissolve. 0.85 g of PVP (AR, Shanghai Aladdin Biochemical Technology Co., Ltd., China) was added slowly to each solution and continue stirring for over 12 h until complete dissolution of PVP. After stirring no visible bubbles remained in the solution. The solutions were transferred into 10 mL syringes and mounted onto a horizontal electrospinning apparatus. The needle tip was set as an anode (11-13 kV) and the aluminum foil collector as a cathode, with an electrode distance of 15 cm. The ambient humidity was maintained at 30%-50% and the solution was fed at a rate of 3 μL/min. The electrospun fibers collected were calcined in a muffle furnace at 600 ℃ for 2 h (at a heating rate of 1 ℃/min). The phase composition was analyzed by X-ray diffraction (XRD, Bruker D8 Advance, 40 kV, 40 mA, Cu-K_α, 5(°)/min, 10°-80°). The microstructure of the samples was determined by scanning electron microscope (SEM) with an accelerating voltage of 15 kV. The elemental valence states of the materials were analyzed by a X-ray photoelectron spectroscopy (XPS, Al K_α, hν=1486 eV).

For the determination of the gas-sensitive properties of La doping ZnFe₂O₄ composite material, the sample was placed in a mortar, and 1-2 drops of turpentine penetration alcohol were added. The mixture was ground until a uniform paste was formed. The paste was then evenly applied onto the surface of an alumina ceramic tube using a small brush. Afterwards, a nickel-chromium heating wire was passed through the ceramic tube and welded to the base of the gas sensor. Finally, the gas sensor was aged at 200 ℃ for 12 h before conducting gas-sensing performance tests.

The XRD patterns show that the grain size is significantly reduced and the gas-sensing performance is improved, indicating that La³⁺ doping inhibits the crystallization process and hinders crystal growth. A reduction in grain size leads to an increase in the specific surface area of the sensor, providing more acetone active sites on the surface of the material. The SEM images show that the surface of La³⁺-doped ZnFe₂O₄ nanomaterials is relatively smooth and cross-linked to form a network structure. The EDS results indicate that the composite material is composed of elements La, Zn, Fe, and O. According to the XPS analysis, La³⁺doping causes a lattice distortion, resulting in an increase in adsorbed oxygen on the material surface. The more oxygen is adsorbed on the surface of the material, which in turn improves the gas-sensing performance. Based on the analysis of UV-visible absorption spectroscopy and the corresponding band gap, the sample LZF-8 has a narrower band gap, indicating that the energy required for electron transition is lower, which is beneficial to electron migration, thereby shortening the response/recovery time. The response value of sample LZF-8 to 0.1 g/L acetone at room temperature is 21.3, which is 11.5 times greater than that of pure ZnFe₂O₄. Meanwhile, the selectivity and sensitivity of the material to different gases at room temperature are investigated. The results show that the sample LZF-8 has good selectivity and detection limit for acetone, with the minimum detection limit of 0.00001 g/L, proving that the prepared sensor LZF-8 has a great application potential.

ZnFe₂O₄ composites doped with different proportions of La³⁺ were prepared via electrospinning. Based on the analysis of the XRD patterns, SEM images, and XPS spectra, La³⁺ was successfully doped into ZnFe₂O₄. The results of gas-sensing test showed that as 8% La³⁺ was doped, the response value (i.e., R_a/R_g = 21.3) to 0.1 g/L acetone at room temperature was approximately 11.5 times greater than that of pure ZnFe₂O₄ (R_a/R_g = 1.7), with the response/recovery time of 27.0 s/10.7 s, and the minimum detection limit of acetone concentration of 0.00001 g/L. This composite gas sensor could have a great potential for efficient detection of acetone gas under room temperature conditions.

This review systematically compares the advantages and disadvantages of various synthetic methods. The existing challenges such as complex synthesis processes, high production costs, significant impurity content in products, non-uniform morphology, and a tendency toward particle agglomeration remain prominent. Exploring low-cost silicon and organic carbon sources with effective impurity removal capabilities and tunable morphological properties thus represents a key direction for future research and development. Furthermore, the construction of core-shell and other structures can solve a problem of agglomeration. Consequently, advancing composite phase preparation technologies and designing sophisticated nanostructures, including core-shell configurations, are anticipated to be critical future developments. Elucidating the influence of key parameters (i.e., gas-phase partial pressure ratios) on the growth behavior of one-dimensional SiC materials, and establishing a process-morphology correlation model through molecular dynamics simulations can enable a precise control over product characteristics and hold a substantial potential for future applications.

Thermal barrier coatings (TBCs) are crucial for protecting aero-engine components against high-temperature and corrosive environments. Conventional yttria-stabilized zirconia (YSZ) coatings undergo phase transformation and degradation at high temperatures of > 1250 ℃, while accelerating their failure process particularly under Ca-Mg-Al-Si (CMAS) attack. The emergence of high-entropy ceramics can give an effective pathway for the development of advanced thermal barrier coating materials. Some studies demonstrate that the incorporation of multiple rare-earth elements endows high-entropy rare-earth zirconates with a lower thermal conductivity, a better phase stability, and a superior corrosion resistance, compared to YSZ. However, the existing research predominantly focuses on rare-earth zirconate materials or process optimization of conventional YSZ coatings, while studies on the atmospheric plasma spraying (APS) preparation process of high-entropy rare-earth zirconate coatings as well as their CMAS erosion behavior and dynamic reaction mechanisms remain insufficient. This study was to thus investigate the CMAS erosion behavior of atmospheric plasma-sprayed high-entropy rare-earth zirconate (Eu_0.2Gd_0.2Er_0.2Tm_0.2Yb_0.2)₂Zr₂O₇ thermal barrier coatings. In addition, the regulatory mechanism of high-entropy design on the CMAS erosion resistance of the coatings was also revealed via systematically analyzing the microstructural evolution, phase transformation, and chemical reaction kinetics under high-temperature CMAS environments.

High-entropy (Eu_0.2Gd_0.2Er_0.2Tm_0.2Yb_0.2)₂Zr₂O₇ (EGETYZ) powder was synthesized via solid-state reaction and subsequent spray granulation to produce spherical particles suitable for APS. Coatings were applied on nickel-based alloy substrates with varying spraying distances (i.e., 80, 100 mm and 120 mm) to optimize the microstructure. The CMAS corrosion tests were conducted at different temperatures (i.e., 1300, 1400 ℃ and 1500 ℃) with a synthetic CMAS composition (33CaO-9MgO-13AlO_1.5-45SiO₂). The phase composition was analyzed by X-ray diffraction (XRD), the surface roughness was determined by laser confocal microscopy (LCM), and the microstructure/elemental distribution was characterized by scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS).

The results show that the high-entropy zirconate coating exhibits a defect-fluorite structure with a minimal surface roughness (2.72 μm) and a low porosity (10.10%) at an 80 mm spraying distance. At 1300 ℃, the CMAS corrosion forms a dense reaction layer of apatite and fluorite, effectively limiting a penetration (i.e., 19.7 μm after 5 h). At 1400 ℃, a three-layer reaction structure emerges, with an increased penetration (i.e., 95.2 μm). At 1500 ℃, a penetration deepeneds significantly (i.e., 321.1 μm), with sparse apatite and prevalent gehlenite and transitional phases. Higher temperatures reduce the CMAS viscosity (by up to 77.57%), accelerating infiltration along coating defects. The dense reaction layer at lower temperatures is a key to corrosion resistance, while a rapid CMAS penetration at higher temperatures hinders its formation.

The EGETYZ coating exhibited the superior resistance to the CMAS corrosion. The corrosion temperature directly affected the viscosity change of CMAS, thereby exerting a significant influence on the corrosion behavior and reaction products. At 1300 ℃, the reaction layer was mainly composed of fluorite and apatite, forming a dense structure that effectively inhibited the CMAS infiltration. At 1400 ℃, the EGETYZ at the bottom of the reaction layer was not completely melted. The elements Al/Mg enriched in the gaps, in synergy with elements Ca/Si/RE, form a rare-earth gehlenite solid solution, resulting in a three-layer structure of the reaction layer (i.e., pure fluorite at the top, fluorite and apatite in the middle, and gehlenite-containing phase at the bottom). At 1500 ℃, only a minimal amount of apatite phase appeared, the degree of EGETYZ melting was relatively low, and it was not completely transformed into the fluorite phase, with the gehlenite phase distributing more extensively. To enhance the CMAS corrosion resistance of high-entropy rare-earth zirconate thermal barrier coatings, the key could lie in promoting the reaction with the CMAS to form a continuous and dense reaction layer. All the formed reaction products could effectively consume the CMAS components.

The chloride (Cl^-) binding capability of calcium silicate hydrate (C-S-H) plays an important role in the chloride resistance and, consequently, the service life of concrete used in marine and deicing environments. The synergistic regulation between geometric confinement and electrostatic interactions and its dependence on the Ca/Si ratio remain insufficiently resolved although the existing studies examine either pore structure (accessibility and transport) or interfacial electrostatics (electrical double layer, EDL). This gap is addressed via establishing a coupled pore structure-EDL framework calibrated against a controlled C-S-H series at different calcium-silicon (Ca/Si) ratios, thereby transforming qualitative descriptions into the mechanism-based quantification of chloride adsorption. In this study, systematic measurements and mathematical descriptions were performed to clarify the C-S-H pore structure, surface potential distribution, and chloride binding capacity. Effects of the Ca/Si and chloride concentrations were investigated. The dynamic competition mechanism between pore-scale accommodation and EDL-mediated electrostatic partitioning was quantitatively characterized.

C-S-H gels with different targeted Ca/Si ratios (i.e., 0.6, 1.0, 1.4, and 1.8) were prepared via chemical precipitation with sodium silicate and calcium nitrate in deionized water. After homogenization, the suspensions were adjusted to pH value of ≥ 12 by using 5 mol/L NaOH solution and then transferred to a polytetrafluoroethylene (PTFE)-lined autoclave and crystallized isothermally

at (60 ± 1) ℃ for 14 d. The product was recovered by vacuum filtration using a Büchner funnel, washed for three times with deionized water, and dried in a vacuum oven at 50 ℃ for 72 h. The dried solid was then ground in a ball mill, passed through a 200-mesh sieve, and stored in a desiccator.

The total pore volume and pore-size distribution (PSD) of the C-S-H gels with varying Ca/Si ratios were determined by nitrogen sorption. The characteristic pore diameter and the gel pores below 10 nm, which were most relevant for transport and EDL overlap in C-S-H clusters, were measured. The Zeta potential (ζ) was measured in alkaline media (pH value of 12) over ionic strengths representative of pore solutions (e.g., 0.1-0.5 mol·L^-1 NaCl). The batch adsorption was conducted via equilibrating C-S-H powders in NaCl solutions at (20.0±0.1) ℃ for 14 d. Supernatants were filtered and analyzed by ion chromatography to determine equilibrium Cl^- concentrations, and adsorption capacities were calculated by mass balance and normalized to solid mass. The Gouy-Chapman-Stern (GCS) framework was implemented in cylindrical pores to couple measured ζ at different pore sizes, explicitly accounting for the Stern layer, diffuse layer, the Debye length, and the EDL overlap in nanoscale. The steady-state Poisson-Boltzmann/Nernst-Planck system was solved to obtain spatial electrostatic potentials and local Cl^- concentrations. The total adsorption was computed via integrating the EDL-related concentration profiles at different pore sizes. The model predictions were compared and validated by the experiments.

The C-S-H specimens with varying Ca/Si ratios normally exhibit unimodal gel-type porosity with dominant mesopores of 3-5 nm, accompanied by a tail extending into larger sizes. Increasing Ca/Si leads to densification, and the cumulative volume of gel pores below 10 nm decreases from approximately 0.11 cm³·g^-1 to 0.04 cm³·g^-1 when Ca/Si increases from 0.6 to 1.8. The zeta potential becomes less negative with increasing Ca/Si ratio, changing from -17 mV (at Ca/Si ratio of 0.6) to -10 mV (at Ca/Si ratio of 1.8) in the case of 0.1 mol·L^-1 NaCl. As electrolyte concentration increases from 0.1 mol·L^-1 to 0.5 mol·L^-1, and |ζ|decreases due to the classical EDL compression. The Debye lengths in the 0.3-1.0 nm imply a substantial EDL overlap within the characteristic gel pores (3-5 nm), eliminating the notion of an electroneutral pore core and promoting field-driven partitioning.

The role of Ca/Si ratio in chloride binding behavior reveals a composition-dependent balance. At a low Ca/Si ratio (i.e., 0.6), the large pore volume favors chloride accommodation, while the highly negative surface potential causes a great electrostatic exclusion of Cl^- near the C-S-H walls. Within confined gel pores, overlapping EDLs shift Cl^- towards the pore center and reduce near-surface concentrations, limiting net chloride uptake despite abundant void space. At an intermediate Ca/Si ratio (i.e., 1.0), the pore volume remains high, while |ζ| is moderated, yielding the most favorable balance between geometric access and electrostatic capture. The modeled profiles and measurements both indicate the maximum adsorption capacity at this intermediate Ca/Si composition, consistent with a synergy between transport accommodation and weakened repulsion. At a high Ca/Si ratio (i.e., 1.8), weaker repulsion can, in principle, increase the interfacial adsorption efficiency per unit area, but the gel densification causes a sharp loss of accessible pore volume (i.e., 0.04 cm³·g^-1), becoming a dominant limiting factor for the reduced overall Cl^- uptake.

A model-experiment agreement is established, demonstrating the non-linear Freundlich-like increase of chloride adsorption with solution concentration. The measured ζ and PSD provide a physically interpretable parameter set for quantitative prediction of Cl^- binding capacity of C-S-H. The densification (at a high Ca/Si ratio) or electrostatic exclusion (a low Ca/Si ratio) can dominate Cl^- adsorption, depending on the composition-controlled balance of the effects. The results identify an intermediate composition window that maximizes Cl^- binding via leveraging moderate surface charge and mesoporous access.

Chloride uptake by C-S-H could be controlled by a dual mechanism, i.e., with gel pore geometry dictating accommodation and transport, while EDL electrostatics governing near-surface adsorption. A low Ca/Si ratio (i.e., 0.6) provided large gel pore volumes but suffered great electrostatic exclusion. A high Ca/Si ratio (i.e., 1.8) weakened a repulsion but substantially densified the gel, resulting in a limited adsorption. An intermediate Ca/Si ratio (i.e., ≈1.0) achieved the optimum synergy between pore accessibility and moderated EDL effects, resulting in a peak Cl^- adsorption. The pore structure-EDL coupling framework proposed in this work could quantitatively link pore sizes and surface potential distribution to chloride adsorption capacity and provide actionable targets for binder design to enhance chloride resistance in service. Cementitious binders that preserved a mesopore network enriched in 3-5 nm pores and moderated surface charge exhibited a superior chloride binding capacity.

Lithium orthosilicate (Li₄SiO₄) is considered as the most promising tritium breeder because of its high lithium density, good chemical stability and promising tritium release property. During the operation of a fusion reactor, the tritium breeders can be exposed to harsh condition for a long time, such as high temperature, thermal gradient and irradiation, which causes the degradation of the structure and property. In this work, Li₄SiO₄ pebbles were fabricated by a melt spraying method. The effect of annealing temperature on the microstructure and mechanical property of ceramic pebbles was investigated. The evolution of crush load at high temperatures was analyzed. In addition, the thermal stability of Li₄SiO₄ pebbles was also examined by long- time annealing experiments at high temperatures.

Li₄SiO₄ pebbles were fabricated by a melt spraying process. Firstly, Li₄SiO₄ powder was synthesized by a solid-state reaction. Lithium carbonate and silicon dioxide were mixed by grinding, and the ground powders were calcined at 850 ℃ for 4 h. Li₄SiO₄ ceramic powder was added into a platinum crucible, and heated until the powder melted to liquid. The melt liquid flowed out of the crucible, the droplet size was adjusted via spraying gas flowrate. During flying, the liquid droplets cooled down and formed spherical pebbles due to the surface tension. Finally, Li₄SiO₄ ceramic pebbles could be obtained by thermal annealing.

The microstructure of Li₄SiO₄ pebbles was determined by scanning electron microscopy (SEM). The crush load was measured by a universal testing machine, the pebble size was (1.00±0.05) mm. The chemical analysis was performed by inductively coupled plasma-optical emission spectrometry (ICP-OES).

Li₄SiO₄ pebbles with uniform microstructure and excellent properties are fabricated by a melt spraying process. The suitable annealing temperature is 600 ℃, and the grains grow up and the mechanical properties deteriorate significantly with further increasing the temperature. The fabricated pebbles annealed at 600 ℃ for 2 h display a dense and homogeneous structure with an average grain size of 3.88 μm, and the crush load is 20.7 N. The crush load at a high temperature decreases with the increase of temperature due to the thermal stress and plastic deformation, and the crush load at 700 ℃ is 8.7 N. According to the results of the long-time annealing experiments, the temperature is a key factor affecting the thermal stability of Li₄SiO₄ pebbles. The pebbles show a good mechanical property stability with moderate grain growth by annealing at 500-600 ℃. However, significant structure and property degradation occur due to rapid grain growth by annealing at 700 ℃. The microstructure degradation can be an inherent microstructural instability related to the competition between the densification and the grain growth kinetics, which is enhanced via increasing the annealing temperature.

Li₄SiO₄ pebbles with a fine structure and impressive property were fabricated by a melt spraying process. The pebbles displayed a dense and homogeneous structure with an average grain size of 3.88 μm, and the crush load was 20.7 N by annealing at 600 ℃ for 2 h. The crush load at high temperatures decreased with the increase of temperature. Besides, the Li₄SiO₄ pebbles could become unstable and deteriorate during the long-time annealing at high temperatures, accompanied by significant grain growth and pore evolution. The original isolated spherical pores could deteriorate to produce a crack-like interconnected pore network. Furthermore, the lithium evaporation was enhanced until the temperature reached 900 ℃. The degeneration of structure and properties of Li₄SiO₄ pebbles at > 700 ℃ could be considered in the design and operation of TBM.

The existing domestic research and applications of SiC_f/SiC composites on static parts of turbine engines is not mature yet, and that on rotor parts is still in a preliminary research stage. For instance, the working conditions for the rotor blade are extremely harsh and its configuration is complex, which make the component structure design a core and critical technology. The turbine rotor blade must ensure the structural integrity of the blade body and tenon, as well as the continuity of the fiber in the bearing direction due to the huge centrifugal mechanical load, thereby leveraging a high tensile strength of the fibers. The structural design of turbine rotor thus must consider the characteristics of composite materials, forming a structure/material integration design method.

The upper limit of long-term service temperature for SiC_f/SiC composites based on the third-generation SiC fibers is approximately 1400 ℃. However, the wall temperature requirements for the combustion chambers of the new generation of aero-engines exceed 1600 ℃. To ensure the long-term service reliability of SiC_f/SiC composite hot-end components in high-temperature gas and corrosive environments, the design and preparation of high-quality protective coatings become one of the key breakthroughs in the technological iteration of aero-engine research and development. The development of protective coatings for the hot-end components of the new generation of aero-engines must rely on advanced technologies such as efficient screening and design of new multi-functional coating materials, innovative coating structure design and precise control of coating microstructure, large-scale preparation of coating feedstock powders, and performance evaluation and failure control of coating systems under typical service environments.

In summary, there remains a significant gap between domestic SiC_f/SiC composite materials and protective coatings, as compared with those of the Western developed countries such as the United States. There is an urgent need to systematically and progressively develop the application technology for ceramic matrix composite materials suitable for aero engines, accelerate the establishment of technical reserves, and provide competitive hot-end components materials and technological support for the high-performance aero engines in China.

Dielectric capacitors are indispensable for pulsed power systems due to their high power density, ultrafast charge/discharge capability (>µs), and excellent fatigue resistance. However, their widespread adoption is fundamentally limited by poor energy storage performance, characterized by inadequate recoverable energy density (W_rec) and efficiency (η). To meet the demands of high-performance applications, it is imperative to simultaneously enhance W_rec, η, and breakdown strength (E_b). Among environmentally friendly candidates, BiFeO₃-BaTiO₃ (BF-BT) relaxor ferroelectric ceramics stand out due to their high Curie temperature (T_C ≈ 830 ℃) and large maximum polarization (P_max). However, the intrinsic low E_b of BF-BT ceramics caused from the volatilization of Bi³⁺ and the change in the valence state of Fe³⁺ hinder their energy storage potential. To address these challenges, this work was to use a dual-strategy approach with compositional tailoring and two-step sintering for the preparation of (0.7-x)BF-0.3BT-xSAN relaxor ferroelectric ceramics. The introduction of Sr(Nb_0.5Al_0.5)O₃ into the 0.7BF-0.3BT system was to enhance relaxor behavior and refine the grain size, synergistically boosting both E_b and polarization response. Furthermore, the effect of SAN on the microstructure, dielectric, and energy storage properties was systematically investigated. This could provide research ideas and theoretical basis for improving the energy storage performance of BF-BT ceramics based relaxor ferroelectric ceramics.

The raw materials powders of Bi₂O₃, Fe₂O₃, BaCO₃, TiO₂, SrCO₃, MnO₂, Nb₂O₅ and Al₂O₃ were analytical purity. These powders were precisely weighed according to a stoichiometric ratio, then ground with ethanol in a ball mill at 400 r/min for 12 h prior to drying. The mixed powder with a small amount of sintering aids (MnO₂) was subsequently calcined at 850 ℃. The mixture was further ground for 12 h and dried. The dried powder was compacted by cold isostatic pressing (200 MPa, 2 min) into circular discs (Ф10 mm×1 mm). These discs were placed in covered alumina crucibles to minimize Bi volatilization and thermally treated at 1050-1110 ℃ for 2 min, and then sintered at 1020-1050 ℃. The ceramic sheet was polished for microstructure characterization. After polishing for microstructural analysis, silver electrodes were screen-printed on the both surfaces of the 0.7 mm thick sintered ceramics and fired at 700 ℃ for 20 min for electrical characterization.

The crystal structure of the ceramics was analyzed by X-ray diffraction (XRD). The surface morphology and grain distribution were examined by field emission scanning electron microscopy (FE-SEM) and performed by a software named Nano Measure. The microscopic domain structure of the ceramics was characterized by piezoelectric force microscopy (PFM). The Raman spectra in the range of 90-900 cm^-1 were determined by Raman spectroscopy. The polarization-electric field hysteresis loops (P-E) were measured by a ferroelectric tester on disk-shaped samples (with the sizes of Ф1.5 mm × 0.08 mm).

The XRD patterns reveal that all the (0.7-x)BF-0.3BT-xSAN ceramics exhibit an asymmetric singlet pattern, indicating that the crystal structure is a pseudo-cubic structure. The content of the second phase gradually increases with the increase of x due to the solid solubility limitation of SAN in BF-BT ceramics. The addition of SAN causes the XRD diffraction peaks shifting to higher angles, indicating a significant contraction of the lattice volume. The Raman peaks of ceramics do not show a significant shift in the Raman full spectrum, but the peak half width gradually increases, which is attributed to the increase in structural disorder. The Raman fitting results further indicate that increasing SAN weakens both A—O and B—O bonds, thereby reducing unit cell polarity and increasing local disorder in the BO₆ octahedra. This enhanced disorder facilitates the establishment of local random electric fields, which in turn promotes the formation of polar nanoregions. The SEM images manifest that the SAN results in a significant grain size reduction, especially as the x exceeds 0.14. The PFM results demonstrate that ceramics of matrix and 0.54BF-.3BT-0.16SAN exhibit both strong and weak piezoelectric response nanodomains, and the nanodomains in 0.54BF-0.3BT-0.16SAN exhibit a weaker piezoelectric response. All the ceramics exhibit significant frequency dispersion and diffusion phase transition in their dielectric results, which imply a strong relaxation behavior. Polar, which can be attributed to a synergistic effect from the fine grain size, moderates a dielectric constant, and the presence of highly active nanodomains. Moreover, the measurements of P-E loops under varying freqization-electric field (P-E) hysteresis loops show a significant decrease in the polarization strength of the ceramic with the increase of SAN, which is attributed to the increase of relaxor characteristics. The Weibull distribution fitting results reveal that the breakdown strength (E_b) initially increases and then decreases with increasing x. Specifically, the 0.54BF-0.3BT-0.16SAN ceramic achieves the maximum E_b of 370 kV/cm. The results of cycling tests reveal that the ceramic exhibits robust frequency, thermal, and fatigue stability.

The (0.7-x)BF-0.3BT-xSAN relaxor ferroelectric ceramics with a pseudo-cubic structure were prepared by a two-step sintering method. The addition of SAN led to a contraction of unit cell and a concurrent weakening of both A—O and B—O bonds, consequently reducing unit cell polarity and enhancing local disorder within the BO₆ octahedra. The results of dielectric test indicated that (0.7-x)BF-0.3BT-xSAN ceramics had strong relaxation properties. The 0.54BF-0.3BT-0.16SAN ceramic simultaneously achieved the superior energy storage performance (i.e., W_rec of 3.90 J/cm³ and η of 85.5%) at E_b of 370 kV/cm. Furthermore, the 0.54BF-0.3BT-0.16SAN ceramic exhibited the excellent frequency (i.e., 1-1000 Hz), temperature (i.e., -20 ℃ to100 ℃), and cycling stability (i.e., 10⁵ cycles).

In this paper, 0.99(0.7BiFeO₃-0.3BaTiO₃)-0.01Bi_0.5Na_0.5TiO₃-xLi₂CO₃ (i.e., x = 0, 0.001, 0.003, 0.005; abbreviated as 0Li, 0.1Li, 0.3Li, 0.5Li, BFBTBNT-xLi) ceramics were prepared by a conventional sintering technique. The ceramics gradually changed from the R phase to PC phase structures, and the ceramic with 0.3Li showed obvious coexistences of R and PC phases as the addition of Li₂CO₃ increases. The Curie temperature of Li₂CO₃-doped BFBTBNT-xLi ceramics increases from 483 ℃ to 535 ℃, and the dielectric loss of the samples decreased. The remanent polarization of the ceramics increased with increasing the Li₂CO₃ addition, reaching the maximum value at 0.3Li. Subsequently, the polarization decreased due to the increased coercive field. Li₂CO₃ could enhance the insulation of the ceramics because of the enhanced migration barrier of oxygen vacancies. The ceramic with 0.3Li could be obtained with an optimal piezoelectric constant of 183 pC·N^-1 and a high depolarization temperature of 380 ℃. This material displayed a great potential in high-temperature piezoelectric application.

The 0.99(0.7BiFeO₃-0.3BaTiO₃)-0.01Bi_0.5Na_0.5TiO₃-xLi₂CO₃ + 1% MnO₂ (x = 0, 0.001, 0.003, 0.005; abbreviated as 0Li, 0.1Li, 0.3Li, 0.5Li, BFBTBNT-xLi) ceramics were prepared by a conventional sintering process. The raw materials were weighed according to the stoichiometric ratio and ground for 12 h. After grinding, the ground raw materials were firstly sintered at 720 ℃ for 5 h, and then the mixtures with MnO₂ were further ground for 12 h. After granulating and pressing, the samples were heated at 600 ℃ for 10 h. Afterwards, the samples were heated at 1000 ℃ for 3 h.

The phase structure of the ceramics was analyzed by X-ray diffraction (XRD, Bruker Co., Germany). The microstructures of the ceramics were determined by scanning electron microscopy (SEM, JSM Co., Japan). In order to test the electrical properties of the BFBTBNT-xLi ceramics, the silver paste was coated on the surface of the samples and fired at 800 ℃ for 10 min to form silver electrodes. Afterwards, the dielectric constant and loss as a function of temperature and impedance spectroscopy was determined by impedance analysis (Agilent E4980A). The ferroelectric performance and J-E curves was measured by ferroelectric analysis (Precision Premier II, Radiant Co., USA). The chemical binding state of O was tested by X-ray photoelectron spectroscopy (XPS, PHI Co., USA). The electron paramagnetic resonance measurements were performed by the EPR spectroscopy (EPR, Bruker Co., Germany). The d₃₃ values at room temperature were measured by a quasi-static piezoelectric constant apparatus (ZJ-3A, China). The in-situ d₃₃ values were collected by a quasi-static d₃₃ apparatus (YE2730A, Sinocera Co., China).

The content of the R phase continuously decreased with increasing Li₂CO₃ addition, especially in the sample with 0.3Li. The content of the R phase reduced to 36.28%, which was the MPB. The content of the R phase in the sample with 0.5Li further decreased to 18.76%, while the content of the PC phase increased to 81.24%, indicating that the sample is mainly composed of the PC phase. The microstructure showed that the surface of the sample was smooth without obvious holes, and the ceramic grains were full and the grain boundaries were clear. The addition of Li₂CO₃ could refine the grains, which was beneficial to improving the toughness against breakdown. The Curie temperatures (T_C) of the samples with 0Li, 0.1Li, 0.3Li and 0.5Li were 483, 502, 521 ℃ and 535 ℃, respectively. The dielectric loss of the BFBTBNT-xLi showd a significant increase with increasing temperature, especially when the temperature exceeded 150 ℃. The dielectric loss of the ceramic samples modified by Li₂CO₃ was significantly reduced, especially more significantly in the high-temperature environment. The residual polarization of the ceramics with the addition of Li₂CO₃ increased, reaching a peak value for the ceramic with 0.3Li. The samples exhibited semi-circular complex impedance characteristics, and the resistance of the ceramics decreased with increasing temperature, which was in line with the characteristics of the semiconductor conduction mechanism. The activation energies (E_a) of the ceramics with 0Li, 0.1Li, 0.3Li and 0.5Li were 1.196, 1.218, 1.251 eV and 1.263 eV, respectively. The oxygen vacancies were inhibited with the gradual addition of Li₂CO₃, thereby enhancing the insulating properties of the ceramics. The leakage current of the samples with 0.1Li, 0.3Li and 0.5Li modified by Li₂CO₃ was improved; especially the leakage current of the sample with 0.5Li reduces to 10^-6 A·cm^-2, which was reduced by two orders of magnitude. The d₃₃ values of the ceramics with 0Li, 0.1Li, 0.3Li and 0.5Li were 149, 161, 183 pC·N^-1 and 152 pC·N^-1, respectively, showing a consistent with the residual polarization. The ceramic with 0.3Li exhibited the maximum piezoelectric constant because of the higher residual polarization, fewer oxygen vacancies and leakage current, thus enabling a more complete polarization and demonstrating the optimum piezoelectric performance. The ceramics modified by Li₂CO₃ showed a high-temperature stability, and the de-polarization temperatures (T_d) of the ceramics with 0Li, 0.1Li, 0.3Li and 0.5Li were 350, 370, 380 ℃ and 390 ℃, respectively.

The 0.99(0.7BiFeO₃-0.3BaTiO₃)-0.01Bi_0.5Na_0.5TiO₃-xLi₂CO₃ (x = 0, 0.001, 0.003, 0.005; abbreviated as 0Li, 0.1Li, 0.3Li, 0.5Li) ceramics were prepared by a conventional sintering process. The ceramics gradually changed from the R to PC phase structure as the addition of Li₂CO₃ increased. The ceramic with 0.3Li showed obvious coexistences of the R and PC phases. The content of R phase in the ceramics BFBTBNT-xLi decreased from 78.02% to 18.76%, while the content of PC phase increased from 21.98% to 81.24%. The addition of Li₂CO₃ could refine the grains, which was beneficial to improving the toughness against breakdown. The Curie temperature increased in the ceramics BFBTBNT-xLi doped with Li₂CO₃, and the dielectric loss of the ceramics was significantly reduced, especially at high temperatures. The remanent polarization of the ceramics increased gradually with increasing the Li₂CO₃ addition, reaching the maximum value for the ceramic with 0.3Li. The oxygen vacancies in the ceramics were suppressed as the Li₂CO₃ addition increased, thus enhancing the insulation performances. The piezoelectric constant of the ceramic with 0.3Li was 183 pC·N^-1, and the depolarization temperature was as high as 380 ℃, which could be promising for high-temperature piezoelectric applications.

Compared with dense ceramics, porous ceramics exhibit lower density and acoustic impedance, as well as excellent thermal resistance, enabling their broader application in hydrophones, high-temperature ultrasonic transducer backing layers, biopiezoelectric devices, and related fields. However, conventional fabrication methods for porous ceramics, such as freeze-casting and gelcasting, are often associated with complex processing procedures. The digital light processing (DLP) additive manufacturing technique offers several advantages, i.e., high resolution, rapid curing, uniform surface exposure, and low production cost, making it a promising alternative for fabricating complex porous ceramic structures. Lead-free barium titanate piezoelectric ceramics have attracted much attention due to their favorable piezoelectric performance. In this study, porous barium titanate ceramics with varying porosity levels were fabricated via DLP 3D printing by adjusting the content of polymethyl methacrylate (PMMA) from 0 to 20%. The influence of porosity on the phase structure, microstructure, and electrical properties of the ceramics was systematically investigated.

A ceramic slurry containing 82% barium titanate (BTO), composed of BTO powder (500 nm), photosensitive resin, and dispersant, was mixed with PMMA microspheres (15 μm) at different mass fractions of 5%, 10%, 15% and 20%, respectively. The mixture was homogenized at 2000 r/min by a homogenizer (ZYE, ZYMC-180V) for 2 min. Subsequently, the designed 3D model in STL format was imported into the control computer for DLP printing. The printed samples had dimensions of Ф12mm×2 mm, with a layer thickness of 50 μm. After printing, the green bodies were subjected to a two-step debinding process (i.e., firstly under vacuum and then in an air atmosphere) and then sintered. The sintered samples were ground, polished, and coated with gold electrodes. The poling was performed in an electric field of 3 kV/mm in silicone oil at 60 ℃ for 15 min. The microstructure of the samples was determined by field emission scanning electron microscopy (LYRA 3 XMU, Tescan Co., CZ). The phase composition of the BTO ceramics was determined by X-ray diffraction (X'Pert PRO, PANalytical B.V., the Netherlands). The sample density was determined based on the Archimedes principle. The dielectric properties were measured by precision impedance analysis (6500B, Wayne Kerr Co., UK), while the piezoelectric coefficient (d₃₃) was evaluated by a d₃₃ meter (ZJ-3A, Institute of Acoustics, Chinese Academy of Sciences, China).

The results show that the porosity of barium titanate ceramics gradually increases as the PMMA content increases from 0 to 20%. The porous ceramics exhibit closed, spherical pores, with pore sizes closely matching the particle size of the employed PMMA (approximately 15 μm). The axial shrinkage ratio of the ceramics increases from 11% to 29%, and the radial shrinkage increases from 14% to 26%. This anisotropic shrinkage behavior is attributed to the layer-by-layer printing process, resulting in a greater axial shrinkage relative to the radial direction. Besides, after the introduction of the air phase, the bulk density decreases from 5.7 g/cm³ to 4.5 g/cm³, the porosity increases from 6.0% to 25.7%, and the acoustic impedance reduces from 23.12 MRayls to 15.25 MRayls. Regarding the electrical properties, the piezoelectric coefficient d₃₃ gradually decreases from 223 pC/N to 135 pC/N, and the dielectric constant ε_r declines from 1255 to 407. This is primarily attributed to the reduction in the effective volume fraction of the piezoelectric phase caused via increasing porosity, as well as the non-uniform electric field distribution within the material, which impairs a polarization efficiency. Meanwhile, the dielectric loss tanδ remains in the range of 0.02-0.04, exhibiting minor fluctuations with an increasing porosity and maintaining a low value.

The effect of PMMA content on the microstructure and electrical properties of BTO ceramics was investigated. The piezoelectric constant and dielectric constant of porous barium titanate ceramics both decreased, while the dielectric loss remained a low range as the PMMA content increased, indicating a good stability. An increase in porosity reduced the bulk density of the BTO ceramics, thereby lowering the acoustic impedance and enhancing acoustic impedance matching. DLP-based 3D printing, by combining high precision with rapid prototyping capability, could provide an efficient and cost-effective route for the fabrication of porous BTO ceramics in acoustic device applications.

The photoluminescence (PL) of rare-earth-doped materials is predominantly controlled by the local crystal field symmetry around rare-earth ions. Using electric fields (E) to modify the PL properties is particularly intriguing as it is compatible with modern electronics and is promising for advanced applications in optical information storage and communication. It is reported that the E-induced structural evolution in host ferroelectrics (FEs) can effectively manipulate the crystal field environment surrounding rare-earth ions, consequently enabling a dynamic modulation of PL intensity (i.e., the E-PL effect). However, the hysteresis behavior in FEs limits the PL modulation range. Antiferroelectrics (AFEs) show a reversible AFE-FE phase transform with zero remanent polarization, particularly promising for realizing reversible E-PL modulation with large tunability. In AFE thin films, the clamping effect from the substrate may exert a significant influence on the structural evolution during the E-induce phase transition. Therefore, compared with the ceramic forms, it is possible to analyze distinct E-PL behavior in rare-earth doped AFE thin films.

1% Er³⁺-dopedPb_0.98La_0.02Zr_0.95Ti_0.05O₃ (PLZT-Er) thin films were prepared on Pt/Ti/SiO₂/Si substrates by a sol-gel/spin-coating method with lead acetate trlhydrate (PbC₄H₆O₄·3H₂O, 99.99%(379.33), Aladdin Co., China), lanthanum nitrate hexahydrate (LaN₃O₉·6H₂O, 99%(433.03), Aladdin Co., China), erbium trinitrate pentahydrate (Er(NO₃)₃·5H₂O, 99.9%(443.37), Aladdin Co., China), zirconium propoxide (C₁₂H₂₈O₄Zr, 70%(327.56), Aladdin Co., China), and titanium butoxide (C₁₆H₃₆O₄Ti, ≥99.0%(340.32), Aladdin Co., China) as the raw materials. The crystal structure was characterized by X-ray diffraction (XRD, Ultima III, Rigaku Co., Japan). The surface morphology was observed using atomic force microscopy (AFM, ICON, Bruker Co., Germany). The polarization (P-E) and current (I-E) loops were measured by a ferroelectric analyzer (AIX ACT, TF2000) at 1 kHz. The down-conversion photoluminescence (DCPL) emission spectra were measured by fluorescence spectroscopy (ULS2048x64TEC, Avantes Co., the Netherlands) under 405 nm and 532 nm laser excitation. For the E-PL tests, 20 nm-thick transparent indium tin oxide (ITO) top electrodes were deposited on the surfaces of PLZT-Er thin film by magnetron sputtering in argon atmosphere (2.0 Pa) at 320 wd3.

The structural, PL, and E-PL properties of PLZT-Er AFE thin films are systematically investigated. The XRD patterns confirm a pure perovskite structure with a lattice shrinkage due to the substitution of Er³⁺ at A-sites, whereas the AFM analysis reveals a smooth surface with a roughness of approximately 3 nm. The double P-E loop and characteristic I-E peaks verify the AFE nature of PLZT-Er thin films, with reversible AFE→FE transitions at ±452 kV·cm^-1 and FE→AFE transitions at ±199 kV·cm^-1. Under 405 nm excitation, the PLZT-Er exhibits 487 nm (⁴F_7/2→⁴I_15/2) and 610 nm (⁴F_9/2→⁴I_15/2) emissions, whereas an excitation at 532 nm induces 560 nm (⁴S_3/2→⁴I_15/2), 660 nm (⁴F_9/2→⁴I_15/2), and 850 nm (⁴S_3/2→⁴I_13/2) emissions, all originating from efficient energy transfer and relaxation of Er³⁺ ions. The reults of E-PL tests demonstrate a remarkable reversible modulation. In 830 kV·cm^-1, the emission at 487 nm shows an 85.14% reduction, with stable switching over six cycles. This performance outperforms PLZT-Er ceramics (+30% modulation) and most reported FE/AFE materials, which is attributed to their higher breakdown strength. The opposite E-PL tuning compared to PLZT-Er ceramics is explained by increased local crystal field symmetry around Er³⁺ ions, arising from either substrate clamping-induced antiferroelectric orthorombic →ferroelectric orthorombic phase transition or incomplete ferrielectric→antiferroelectric transition in an insufficient electric field. These findings highlight the PLZT-Er thin films as promising candidates for optical information storage and communication devices.

Er³⁺-doped Pb_0.98La_0.02Zr_0.95Ti_0.05O₃ (PLZT-Er) thin films exhibited a reversible electric-field-modulated photoluminescence (E-PL) effect. Under 405 nm laser excitation, a PL reduction of -85% could be achieved in an applied electric field of 830 kV·cm^-1. This negative E-PL tuning trend was anomalously opposite to that in bulk PLZT-Er ceramics. Two potential mechanisms could be proposed to explain this anomalous phenomenon, i.e., either the antiferroelectric orthorombic (AFE_O) to ferroelectric orthorombic (FE_O) phase transition or the incomplete ferrielectric (FiE) to antiferroelectric (AFE) phase transition in PLZT-Er thin films could increase the local crystal field symmetry around Er³⁺ ions.