Cement production accounts for approximately 12% of China's total CO₂ emissions, having a significant challenge to achieving the national "dual carbon goals". Carbon capture, utilization, and storage (CCUS) represent a pivotal innovative technology for mitigating these emissions. However, conventional amine-based CO₂ capture requires an energy-intensive high-temperature desorption, hindering its industrial implementation in cement plants. Also, the limited utilization pathways for captured CO₂ pose another challenge for cement CCUS. Diethanolamine (DEA) offers a promising solution as it functions both as a CO₂ absorber and a cement additive. This dual capability enables a potential carbonation utilization of CO₂ absorbed DEA solutions without requiring the desorption step within cementitious systems. This study was thus to investigate the effect of CO₂-absorbed diethanolamine (DEAC) on the early hydration behavior and strength development of cementitious systems. The findings could propose a novel approach for low-energy CO₂ capture coupled with efficient in-situ utilization within cement industry.

Cement mortars with a water-to-cement ratio (W/C) of 0.50 were prepared with P·I 42.5 Portland cement (GB 8076) and ISO standard sand. The specimens were designated as REF, D0.1%C0%, D0.1%C0.02%, D1.0%C0%, and D1.0%C0.22%, respectively. DEA and its equivalent CO₂ admixture were added as percentages of cement mass. All associated cement paste mixtures were prepared at a W/C ratio of 0.3. DEAC was prepared by continuously bubbling CO₂ gas (≥99% purity) at a flow rate of 200 mL/min through a 5 mol/L DEA solution maintained at 40 ℃ until saturation was achieved. An eight-channel microcalorimeter recorded the hydration heat of cement paste specimens at 25 ℃ for 72 h. The phase composition of hardened cement pastes was determined by X-ray diffraction (XRD). The contents of bound water, CH, and CaCO₃ were analyzed by thermogravimetric analysis (TGA). The cumulative porosity and pore size distribution of hardened paste samples at 7 d were characterized by mercury intrusion porosimetry (MIP). The compressive strength was measured on mortar specimens at 1, 3 d and 7 d of curing in accordance with the standard GB/T 17671.

The hydration calorimetry results demonstrate that D0.1%C0.02% and D0.1%C0% both accelerate the hydration rate of silicate phases, as evidenced by an increased second exothermic peak rate, while leaving the induction period duration unaffected. Conversely, D1.0%C0% and D1.0%C0.22% significantly reduce the second exothermic peak rate. D1.0%C0.22% extends the hydration induction period to 240 min, while D1.0%C0% has a negligible effect on its duration. The XRD patterns and TG analyses reveal that the impact of DEAC on the cement hydration depends critically on its specific DEA and CO₂ dosage. At a low dosage (i.e., D0.1%C0.02%), a mild carbonation promotes a concurrent hydration of silicate and aluminate phases. However, a high dosage (i.e., D1.0%C0.22%) substantially inhibits early hydration of silicates. The MIP results indicate that DEAC and DEA both refine the pore structure of hardened cement paste. The pores below 20 nm are significantly reduced in D0.1%C0% and D0.1%C0.02% systems, aligning with their enhanced early hydration kinetics. This refinement also occurres in D1.0%C0% and D1.0%C0.22% systems despite inhibited silicate hydration. The results of compressive strength tests show that D0.1%C0.02% and D0.1%C0% can enhance mortar strengths at 1, 3 d, and 7 d, respectley. The strengths of D0.1%C0.02% systems can be increased by 8.4%, 10.2%, and 16.8% at these ages, respectively, primarily due to the DEA component with the weak carbonation contributing minimal additional enhancement. The 3-day and 7-day strengths of D1.0%C0.22% and D1.0%C0% systems both are increased (more significantly in the carbonated system), indicating a synergistic hydration-carbonation effect. However, the 1-day strength of D1.0%C0.22% system drastically is reduced by 52.2%, with silicates hydration inhibition by D1.0%C0% identified as a primary factor underpinning early strength reduction. According to the analysis of bound water content, calcium hydroxide (CH) content, porosity, and compressive strength relationships, a linear correlation between CH content and mortar strength is proposed. This demonstrates that silicate phase hydration kinetics can be modulated differently by DEAC and DEA formulations-fundamentally governed compressive strength development.

The addition of 0.1%DEA with 0.02% CO₂ (D0.1%C0.02%) as DEAC enhanced the flexural and compressive strengths of cement mortar at 1, 3 d, and 7 d. In contrast, the addition of 1.0% DEA with 0.22% CO₂ (D1.0%C0.22%) significantly reduced the 1-day strength. In D0.1%C0.02% system, the CO₂ component reacted with dissolved Ca²⁺ released from cement minerals to precipitate CaCO₃. This reaction promoted cement hydration, refined the pore structure of the hardened paste by reducing the volume of harmful pores, and facilitated a synergistic enhancement of hydration and carbonation. D1.0%C0.22% addition significantly retarded cement hydration within the first 24 h, primarily by inhibiting the dissolution of silicate phases and extending the induction period, leading to the reduced early strength. Although carbonation exacerbated the retardation of silicate phase hydration via DEA interaction, the hydration process recovered normal kinetics after 7 d.

In transition towards a decarbonized energy system globally, hydrogen plays a crucial role as a zero carbon energy carrier. In this context, solid oxide electrolysis cell (SOEC) technology with its advantages in high-temperature operation significantly reduces material costs and improves overall system energy efficiency, compared to low-temperature solutions such as alkaline and proton exchange membrane electrolysis. SOEC system adopts a non-precious metal ceramic structure. When operating at 650-1000 ℃, electrochemical kinetics acceleration mechanism achieves a conversion efficiency of > 80%, providing a feasible approach to reduce cost of green hydrogen leveling. The existing domestic demonstration projects are limited to a scale of tens to hundreds of kilowatts, and the commercial implementation needs to break through bottleneck of "three highs and one low", thus increasing power density of fuel cell stack, extending its service life, and optimizing system integration, while reducing assets and operation and maintenance costs. Solving these obstacles requires collaborative efforts in three major fields, and innovation in materials and structures must break through conventional design framework of electrodes, electrolytes, and sealing glass. With precise microstructure design and interface stress control, system can maintain a high current density of 2 A·cm^-2, while controlling degradation rate at 1 mV per thousand hours, significantly extending lifespan of battery pack. Multi-energy coupling optimization is crucial, which requires integrating the SOEC with industrial waste heat and renewable resources, thus utilizing low-grade thermal energy (i.e., 200-300 ℃), efficiently offsetting internal heating demand, reducing external electricity consumption by approximately 30%, and comprehensively improving energy utilization efficiency. For those localized supply chains, establishing a complete domestic production capacity from precursor powder to single cell manufacturing, stacking and assembly to system integration is particularly crucial. The goal is to control stacking cost at RMB 2500 per kW and achieve an operating life of 5×10⁴ h, laying a foundation for large-scale applications. At present, although the SOEC has significant energy efficiency advantages, its promotion and application still face multiple constraints, i.e., gradual decay of oxygen electrodes under high temperature and high vapor partial pressure, mechanical and electrochemical damage caused by power fluctuations, and daunting initial capital investment. Subsequent exploration should focus on preparing new electrode materials with a higher stability, establishing flexible thermoelectric synergistic regulation mechanisms to adapt to fluctuating renewable energy, and promoting standardization and cost reduction and efficiency improvement throughout entire industry chain. The cost of photovoltaic and wind power continues to decrease, coupled with increasing demand for green hydrogen in chemical and metallurgical fields. Solid oxide electrolysis cell technology is expected to be widely applied in "electricity hydrogen ammonia/methanol" integrated system, distributed energy system, and sustainable refining scenarios. This technology will undoubtedly become a key pillar technology supporting the dual carbon goals in China.

The Faraday effect was discovered 180 years ago, but this phenomenon has been still utilized for practical applications as mentioned above. In particular, Tb³⁺-rich and Eu²⁺-rich oxide glasses are important for both fundamentals and applications. The Tb³⁺-rich glasses show a high transparency even in blue to ultraviolet region, so that the magneto-optical figure of merit is large enough to apply for an optical isolator. The Eu²⁺-rich glasses are ferromagnetic, so that they notably show a large Faraday effect. A new technique of glass formation such as containerless processing is effective to produce new glass compositions with further higher concentrations of rare-earth ions that are expected to exhibit a larger Verdet constant. Besides, the possible enhancement of Faraday effect based on plasmonics and Mie-tronics, i.e., the usage of localized surface plasmon resonance of metal nanoparticles and the Mie resonance of dielectric nanoparticles to increase the Verdet constant, becomes an important subject in the near future. With the development of high-power lasers, the demand for optical isolators that can operate in a wide wavelength range must increase. The oxide glasses have a promising application in such fields.

Although composite titanium salt coagulants demonstrate excellent performance, there are still some issues and challenges that need to be addressed. Future research can focus on the following aspects: (a) Enhancing Adaptability to Real Water Bodies. Currently, the complex composition of various actual water bodies imposes higher demands on the application of composite titanium salt coagulants. To ensure stable and efficient coagulation performance under complex water quality conditions, future efforts should focus on developing novel composite titanium salt coagulants with stronger specificity and broader applicability, thereby meeting the needs of more complex and demanding application scenarios. (b) Lower- Cost Preparation of Composite Titanium Salt Coagulants. At present, the preparation of composite titanium salt coagulants largely relies on complex processes such as SAT, ED, and sol-gel methods, which hinders their large-scale application. Future research should aim to develop simpler, greener, and more economically viable preparation pathways—for instance, utilizing industrial by-products or waste materials as raw materials—while optimizing the preparation process to reduce energy consumption and production costs. (c) Ensuring Ecological and Health Safety. Current research on the toxicity assessment of titanium-based coagulants has predominantly focused on TiCl₄ and Ti(SO₄)₂. Future studies should strengthen investigations into titanium residue and its ecotoxicological effects during the use of composite titanium salt coagulants. Meanwhile, it is essential to employ a wider range of aquatic organisms (e.g., fish, shellfish, and aquatic plants) for ecotoxicity studies, and to further explore the migration, transformation, and long-term accumulation of residual titanium in water bodies and organisms. This will provide a scientific basis for comprehensively safeguarding water environments and human health.

It is effective to introduce self-healing components, network intermediate oxides and rare-earth silicates into the SiC_f/SiC composite matrix to fill the pores and cracks of the material via generating self-healing components during the oxidative corrosion process, and forming a dense oxide layer on the surface of the material to resist further erosion by the oxidizing medium, thus improving the water and oxygen corrosion resistance of the composites. However, there are still some challenges. Firstly, the research on the oxidation corrosion mechanism of composite materials is still in-depth, and there is a lack of data on oxidation kinetics, oxidative corrosion rate and oxidative corrosion depth, and the basic research on the damage evolution mechanism of materials in different environments is still relatively weak. It is thus necessary to construct a complete and reliable performance database of SiC_f/SiC composites modified with different substrates, clarify the oxidative corrosion damage mechanism, and provide design parameters and theoretical support for the practical application of composites. Secondly, the effective temperature range of a single modified substance to improve the oxidative corrosion performance of composites is limited. The temperature range of B group is below

1000 ℃, and the temperature range of Al group is 1000-1300 ℃. The synergistic effect of multiple modification strategies is explored via introducing multiple modified substances into the matrix of composites at the same time. It is expected to achieve the oxidation and corrosion properties of SiC_f/SiC composites in a wide temperature range and achieve a long-life cycle protection. Finally, it is also worth to develop new preparation processes, such as nano-infiltration and transient eutectic (NITE), or use hybrid processes to achieve material densification and improve the performance of SiCf/SiC composite substrates while modifying them.

High-temperature vibration sensors are indispensable key components for the health detection of core equipment in fields such as aerospace and nuclear energy. The BiScO₃-PbTiO₃(BS-PT) system has attracted much attention due to its high Curie temperature (T_C≈450 ℃) and excellent piezoelectricity (d₃₃≈450 pC/N). However, the poor insulation properties of this material hinder its application in high-temperature vibration sensors because high electrical resistivity (ρ) and a long time constant (τ) are critical to prevent thermal runaway and ensure signal integrity. Manganese (Mn) doping is a commonly used modification method for piezoelectric ceramics. Previous studies on Mn-doped BS-PT were controversial regarding the valence state distribution and substitution positions of Mn ions, which could not be conducive to the design of high-temperature piezoelectric ceramics with the collaborative optimization of multiple electrical parameters. Therefore, this work was to clarify the defect chemical mechanism associated with manganese doping through refined structural characterization combined with electrical performance analysis, and to obtain the modified BS-PT piezoelectric ceramic components suitable for high-temperature vibration sensors.

0.365BiScO₃-0.635PbTiO₃-x% MnO₂ (BSPT-x% MnO₂, x=0.00, 0.01, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00) ceramics were synthesized by a conventional solid-state reaction method. The powders were firstly calcined at 800 ℃ for 2 h and then sintered at 1050 ℃ for 2 h. The phase composition was analyzed by X-ray diffraction (XRD). The rietveld refinements were performed using a software named GSAS. The microstructure and elemental distribution were examined by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The average grain size was estimated by a software named Nano Measurer. The Mn valence states were determined by X-ray photoelectron spectroscopy (XPS). For electrical measurements, poled samples (120 ℃, 5 kV/mm, 30 min) were used. The piezoelectric coefficient (d₃₃) was measured by a model CAS ZJ-6A quasi-static meter. The electromechanical coupling coefficient (k_p) was measured by a model Agilent 4294A impedance analyzer. The temperature-dependent dielectric properties were measured by a model Agilent E4980A LCR analyzer. The high-temperature DC resistivity (ρ) was measured by a model Keithley 6517B high-resistance electrometer. The in-situ d₃₃ was measured by a model Julang TZFD-600 variable temperature quasi-static d₃₃ measurement system.

The Mn doping mechanism and high-temperature performance of BS-PT ceramics are systematically clarified. The XPS results confirm the coexistence of Mn²⁺ and Mn³⁺. To quantitatively verify the substitution site, the rietveld refinement reveals a non-monotonic evolution of unit cell volume. Based on the EDS evidence of Sc segregation without Ti precipitation, Mn ions preferentially substitute for B-site Sc³⁺. The dominant aliovalent substitution introduces defect dipoles accompanied with strong local random electric fields, significantly enhancing a relaxor behavior, while triggering a "hardening" effect that reduces tanδ and ε_r. The decoupling of piezoelectric and dielectric properties is achieved in specific compositions due to the grain boundary effect compensating for the hardening effect, especially obtaining the optimal piezoelectric voltage constant (g₃₃) at the component with x of 1.00. For high-temperature capabilities, the optimal composition (x=1.00) demonstrates a superior stability, with in-situ d₃₃ variation remaining within 20% up to 400 ℃. The thermally stable defect dipoles effectively trap oxygen vacancies, leading to a high resistivity of 10⁹ Ω·cm and an enhanced time constant of 0.072 s at 350 ℃. Consequently, the ceramic with x of 1.00 exhibits a high g₃₃ of 0.012 V·m/N when evaluated at a unified service temperature of 350 ℃, which is 50% higher than that of the undoped counterpart. These results indicate that the modified ceramic achieves an optimal balance of sensitivity and insulation for high-temperature vibration sensors.

This work clarified the Mn doping mechanism in BS-PT ceramics. The results of correlative XPS, Rietveld refinement, and EDS analysis confirmed that Mn ions could preferentially substitute for B-site Sc³⁺. The dominant aliovalent substitution induced a hardening effect, while the recovery of d₃₃ was dominated by grain size restoration. The optimal composition (x=1.00) exhibited a robust stability with d₃₃ variation within 20% at 400 ℃. The thermally stable defect dipoles could obtain a high resistivity (10⁹ Ω·cm) and time constant (0.072 s) at 350 ℃. Meanwhile, a superior piezoelectric voltage coefficient (g₃₃) of 0.012 V·m/N was achieved at 350 ℃, which was 50% higher than that of the undoped counterpart, validating its potential for high-temperature sensors.

With the continuous pursuit of higher efficiency and larger thrust-to-weight ratio in aero-gas-turbine engines, the turbine inlet temperature has already exceeded 1300 ℃, imposing increasingly stringent requirements on the thermal resistance and protective capability of hot-section structural materials. Environmental barrier coatings (EBCs) have become a crucial technology to ensure efficient and reliable service of ceramic matrix composite (CMC) turbine components under such extreme working conditions. However, the service environment of EBCs is exceptionally complex. Coatings are continuously exposed to corrosive gaseous species within combustion products, among which the ingression and reaction of molten calcium-magnesium-aluminum-silicate (CMAS) deposits represent one of the most detrimental degradation mechanisms.

To mitigate CMAS-induced deterioration, numerous strategies have been proposed, including compositional modification (doping, high-entropy ceramics), structural design optimization (multilayer or graded coatings), and surface engineering (laser or ion beam treatments). Although these approaches can improve corrosion resistance to some extent, most of them inevitably alter the coating chemistry or structural system, which tends to induce thermal expansion mismatch with the substrate and promotes premature failure during thermal cycling. Therefore, how to enhance CMAS-corrosion resistance while maintaining thermomechanical compatibility remains a critical challenge. Laser glazing (LG) is a surface-modification technique that locally melts and rapidly solidifies the coating surface to form a dense glaze layer. It improves surface compactness and seals microdefects without altering the coating composition, thereby presenting a promising method for improving CMAS-corrosion resistance. In this work, laser glazing is introduced to enhance the CMAS-resistance of EBCs, and the CMAS-corrosion behavior together with the underlying improvement mechanisms are systematically investigated.

SiC ceramic substrates were purchased from Fuzhou Pengkun Optoelectronics Co., Ltd. The samples were cylindrical (diameter 25.4 mm, thickness 3 mm) and mechanically grit-blasted prior to coating deposition. Yb₂Si₂O₇/Si (YbDS) EBCs were deposited on the substrates by atmospheric plasma spraying (APS). Commercial Yb₂Si₂O₇ and Si powders (Shanghai Shuitian Materials Technology Co., Ltd.) were used, and the bond coat consisted of 90% (in mass fraction) Si and 10% Yb₂Si₂O₇. A picosecond ultraviolet pulsed-laser system was subsequently applied to modify the surface microstructure of APS YbDS coatings. Four sets of parameters (L1-L4) were obtained by adjusting the laser power (6 W or 20 W) and scanning speed (100-300 mm/s). CMAS bulk material was synthesized by high-temperature melting. CMAS powder was mixed with ethanol and uniformly brushed onto the coating surface, followed by drying to achieve a coating mass of 5 mg/cm². The coated samples were exposed at 1350 ℃ for 10, 60 h, and 120 h. After corrosion, the evolution of microstructure and phase composition was analyzed to reveal the degradation behavior.

The APS-prepared YbDS coating exhibited a surface roughness of ~3.7 μm and a porosity of ~4.87%, with typical APS defects such as pores, unmelted particles, and microcracks. After laser glazing, four modified surfaces were obtained. Among them, sample L2 demonstrated the most favorable structural morphology and was selected for subsequent corrosion tests. The L2 coating showed a reduced surface roughness of ~1.824 μm and a homogeneous, dense glaze layer of ~9.6 μm thickness. Moreover, the glazed surface phase completely transformed from Yb₂Si₂O₇ to Yb₂SiO₅. During CMAS corrosion, the YbDS coating surface was continuously covered by a loose mixture of Ca₂Yb₈(SiO₄)₆O₂ and CMAS residual glass. In contrast, the laser-modified L2 coating was covered by a compact Ca₂Yb₈(SiO₄)₆O₂ reaction layer. After corrosion, both coatings displayed Ca₂Yb₈(SiO₄)₆O₂ and secondary Yb₂Si₂O₇ phases; however, their structural evolution differed significantly. After 120 h of corrosion, the YbDS coating suffered severe structural degradation, including interfacial delamination and partial spallation in cross-sectional observations. Conversely, the L2 coating maintained structural integrity, and its corrosion depth was consistently lower under the same conditions.

The improved CMAS resistance of the L2 coating can be attributed to three synergistic mechanisms: Surface densification, Laser glazing produced a dense, continuous glaze layer that sealed APS-induced pores and cracks, effectively delaying CMAS infiltration pathways; Protective reaction-layer formation, The Yb₂SiO₅ glaze reacted with CMAS to form a dense Ca₂Yb₈(SiO₄)₆O₂ layer, which further hindered molten-salt penetration ;Enhanced non-wettability, Laser glazing significantly reduced surface roughness and improved hydrophobicity. As a result, molten CMAS appeared as aggregated hemispherical droplets rather than fully spreading, making it more easily removed by high-velocity gas flow during service.

The findings of this study demonstrate that laser glazing effectively enhances the CMAS-corrosion resistance of YbDS coatings. The improvement originates from the combined effects of surface densification, pore/crack sealing, phase transformation to Yb₂SiO₅, and subsequent formation of a compact Ca₂Yb₈(SiO₄)₆O₂ reaction layer during corrosion. Additionally, the smoother and less wettable glazed surface reduces the adhesion and spreading tendency of CMAS, enabling molten deposits to be removed more easily under aerodynamic forces. As a result, the degradation rate of the coating is substantially suppressed, delaying the propagation of corrosion-induced cracks and maintaining structural integrity over prolonged exposure. Moreover, the laser-induced modifications do not alter the coating architecture or introduce thermal expansion mismatch, making the technique compatible with existing EBC design frameworks. Overall, laser glazing represents a promising strategy for improving the durability and service lifetime of EBC systems in next-generation high-temperature aero-engine applications.

In summary, with the increasing service temperature of aero-engines, the abradable/environmental barrier coatings (A/EBCs) that match SiC_f/SiC ceramic matrix composites (CMCs) become a key research direction. This review represents the research progress of A/EBCs in material design, microstructural regulation and performance evaluation, and points out that the current challenges mainly include thermal expansion mismatch between conventional coating materials and CMC substrate, poor high-temperature stability of lubricants, difficult balance between multi-scale pore structure and multi-performance, and lack of standardized evaluation systems and test standards suitable for multi-field coupling service environment. In the future, the research and development of A/EBCs should focus on the multi-objective synergistic design of material composition, multi-scale microstructure and performance evaluation system. It is necessary to strengthen the analysis of failure mechanism under multi-physical field coupling environment, develop new high-temperature stable matrix and lubricant materials, realize the precise regulation of multi-scale pore and interface structure, and establish a standardized preparation and performance evaluation system. Through the breakthrough of the above key technologies, the comprehensive performance and service durability of A/EBCs will be effectively improved, so as to promote the leapfrog development of high-temperature sealing technology and provide an important support for the performance improvement of next-generation aero-engines.

With the advancement of the era, the demand for ultraviolet photodetectors in environmental monitoring and communication security continues to grow, leading to increasingly stringent performance requirements. In this case, self-driven ultraviolet photodetectors emerge to meet the needs of energy conservation and device miniaturization. However, conventional self-driven ultraviolet photodetectors still face some challenges such as low efficiency in photo-generated carrier separation, poor photoresponse performance, and limited response speed. Ferroelectric thin films with a high remnant polarization can form a depolarization field that penetrates the entire bulk material, enabling an effective separation of internally generated photo-generated electrons and holes. This provides a promising solution to the aforementioned issues. Pb(Zr_xTi1-x)O₃(PZT) is a typical ABO₃-type perovskite ferroelectric material. This material is widely used in ferroelectric memories, micro-electromechanical systems, and photodetectors due to its excellent ferroelectric, piezoelectric, and photoelectric properties. Extensive studies show that the composition significantly affects the crystal phase structure and ferroelectric properties of PZT thin films. However, its impact on the photoelectric performance requires a further systematic investigation. This work was to analyze the photoelectric characteristics of PZT thin films with different Zr/Ti ratios, in order to elucidate the influence of compositional modulation on the photoelectric effect.

Pb(Zr_xTi₁-x)O₃ ferroelectric thin films with different Zr/Ti ratios were prepared by a sol-gel method. The selected precursors and solvents were high-purity lead acetate [Pb(CH₃COO)₂·3H₂O], zirconium n-propoxide (C₁₂H₂₈O₄Zr), and titanium isopropoxide (C₁₂H₂₈O₄Ti) as sources for lead, zirconium, and titanium, respectively, glacial acetic acid as a chelating agent, and n-propanol as a stabilizer. Semitransparent gold electrodes were deposited on the surface of the thin films by a model VZZ-300 high-vacuum thermal evaporation system (VANNO Co., China) to fabricate self-driven ultraviolet photodetectors with an Au/PZT/FTO vertical structure. The crystal structure of the films was characterized by a model D8 Advance X-ray diffractometer (XRD, Bruker Co., USA). The surface roughness of the films was determined by an atomic force microscope (AFM, Bruker Dimension Edge Co., USA). The optical properties of the films were analyzed by a model UV-3600 Plus ultraviolet-visible-near-infrared spectrophotometer (UV-Vis-NIR, Shimadzu, Japan). The ferroelectric properties were measured by a model Precision LC II ferroelectric test system (Radiant Co., USA). The current-time (I-t) curves were obtained by a model Keithley 2400 source meter, with a 150 W ultraviolet-enhanced xenon lamp as a light source.

The XRD patterns indicate that the three prepared PZT thin films with different Zr/Ti ratios all exhibit a typical perovskite structure, and no diffraction peaks from impurity phases appear aside from those originating from the FTO substrate. As the Zr content increases, the surface morphology of the films transitions from elongated needle-like structures to island-like structures, and finally to wavy undulations. The lowest root mean square (RMS) roughness of 2.62 nm is obtained at a Zr/Ti ratio of 0.52:0.48. The remnant polarization first increases from 27.9 μC/cm² (Zr/Ti=0.49/0.51) to a maximum of 33.2 μC/cm² (Zr/Ti=0.52/0.48), and then decreases to 31.1 μC/cm² (Zr/Ti=0.55/0.45) as the Zr content increases. A higher remnant polarization is beneficial to forming a stronger built-in electric field, thereby improving the separation efficiency of photogenerated carriers. The PZT films with different Zr/Ti ratios are all wide-bandgap semiconductors (>3.6 eV). As the Zr content increases, the bandgap widens from 3.60 eV to 3.68 eV, showing a blue-shift trend. When a negative poling voltage is applied, the depolarization field inside the PZT aligns with the built-in field induced by the interfacial Schottky barrier, synergistically enhancing the driving force for carrier separation and leading to a significant increase in photocurrent. For the sample with a Zr/Ti ratio of 0.52:0.48 at a poling voltage of -2 V, the responsivity and detectivity reach 3.2 mA/W and 0.33×10¹¹ Jones, respectively. Even under a weak illumination of as low as 0.17929 mW/cm², the device still generates a photocurrent of 1.02 nA, demonstrating the excellent detection sensitivity.

Pb(Zr_xTi₁-x)O₃ ferroelectric thin films with different zirconium-to-titanium ratios (i.e., Zr/Ti=0.49:0.51, 0.52:0.48, 0.55:0.45) were fabricated by a sol-gel method, and self-driven ultraviolet photodetectors with an Au/PZT/FTO structure were constructed. The structural characterization revealed that all PZT thin films exhibited a pure perovskite phase with a good crystalline quality. The AFM analysis indicated that the film surfaces were smooth, dense, and displayed a uniform grain distribution. The ferroelectric property measurements further confirmed that all films with different Zr/Ti ratios showed characteristic ferroelectric hysteresis loops and possessed a high remnant polarization, having a maximum value of 33.2 μC/cm² at Zr/Ti=0.52:0.48. The results of photoelectric tests demonstrated that the device based on this optimal composition exhibited stable and reproducible photocurrent responses. At a poling voltage of -2 V, its responsivity and detectivity were significantly enhanced. In summary, the rational adjustment of the Zr/Ti ratio could effectively optimize both the ferroelectric properties of PZT thin films and the photoelectric characteristics of the corresponding devices. This work could innovatively utilize the inherent bulk depolarization field of PZT ferroelectrics as a driving force to achieve an efficient separation of photogenerated electron-hole pairs. Moreover, it could provide a systematic optimization strategy from the perspectives of compositional design and polarization modulation, offering an effective material- and physics-based solution to overcome the key bottlenecks of low responsivity and detectivity in self-driven ultraviolet photodetectors.

Quartz ceramics (SiO₂) possess unique properties such as low thermal expansion, excellent chemical stability, and outstanding dielectric performance, making them widely used in semiconductor manufacturing, optoelectronic devices, and high-frequency electronic components. Traditional sintering of quartz ceramics typically requires temperatures above 1000 ℃, which inevitably induces polymorphic transformations from α-quartz to β-quartz or cristobalite, hindering the preparation of single-phaseα-quartz ceramics. Recently, the cold sintering process (CSP) has emerged as a promising low-temperature densification route for ceramics, utilizing transient liquid phases to induce "dissolution-precipitation" or interfacial reaction mechanisms. However, for low-solubility ceramics such as quartz, CSP often fails to achieve full densification and crystallization due to insufficient dissolution kinetics and weak interfacial reactivity. The critical scientific problem addressed in this work is how to effectively trigger the amorphous-to-crystalline phase transition of low-solubility quartz at low temperature, thereby enabling the preparation of denseα-quartz ceramics.

This study systematically investigates the cooperative effects of transient solvent alkalinity, sintering temperature, and uniaxial pressure on the amorphous-to-α-quartz phase transition during CSP. A transient alkaline liquid phase is introduced to regulate interfacial reactions and crystallization kinetics, aiming to provide a theoretical basis and technical strategy for the low-temperature processing of low-solubility ceramics.

Amorphous mesoporous silica (SBA-15) powders were used as the starting material. The powders were homogeneously mixed with different transient solvent phases: deionized water (neutral), 5 mol·L^-1 NH₃·H₂O (weak alkaline), and NaOH solutions of varying concentrations (0.5-10.0 mol·L^-1, strong alkaline). Approximately 0.4 g of powder was thoroughly ground with the liquid phase in a mortar and then loaded into a 10 mm diameter steel die. Uniaxial pressures ranging from 200 MPa to 600 MPa were applied, while the sintering temperature was varied between 200 ℃ and 350 ℃. Heating was conducted at a rate of 15 ℃·min^-1 and held for 40 min at the target temperature. After natural cooling, the sintered pellets were mechanically polished for further characterization.

The density of the cold-sintered ceramics was calculated by dimensional and weight measurements using a vernier caliper and electronic balance, and relative density was determined based on the theoretical density of quartz (2.2 g·cm^-3). Phase composition and structural evolution were analyzed using X-ray diffraction (XRD, Cu Kα radiation, λ = 0.154 06 nm, 50 kV, 100 mA, scanning range 10 °-90 °, step size 0.01). Fourier-transform infrared spectroscopy (FTIR-ATR) was used to identify bonding characteristics and confirm phase transitions. Microstructural evolution and fracture features were observed by field-emission scanning electron microscopy (FE-SEM). The mechanical properties of the sintered ceramics were evaluated by Vickers hardness tests (3 kgf load, 10 s dwell), flexural strength using the modified small punch (MSP) method, and fracture toughness (K_IC) calculated by the Anstis equation. Poisson's ratio and Young's modulus were determined by ultrasonic measurements.

This experimental design allows for a systematic investigation of how transient solvent alkalinity, temperature, and pressure cooperatively affect densification and amorphous-to-crystalline transformation during CSP of quartz.

The phase composition of the sintered bodies was strongly influenced by the type and concentration of transient solvent. Without a liquid phase or with neutral water, the sintered samples remained largely amorphous and exhibited low relative density (~80%). Weak alkaline NH₃·H₂O increased compaction and relative density (~92%) but failed to trigger phase transformation. In contrast, strong alkaline NaOH solutions (≥3 mol·L^-1) effectively promoted the dissolution of Si-OH surface species, forming soluble silicate intermediates. These intermediates subsequently underwent reprecipitation and recrystallization under external pressure and temperature, leading to complete transformation into α-quartz at 300 ℃ and 500 MPa. XRD and FTIR confirmed the disappearance of the amorphous broad peak and the emergence of α-quartz characteristic double peaks at 798 cm^-1 and 778 cm^-1, indicating a complete amorphous-to-α-quartz transition.

A clear alkalinity-dependent phase transition sequence was identified: amorphous → keatite (0.5 mol·L^-1 NaOH) → keatite +stishovite (1 mol·L^-1) → keatite + α-quartz (3 mol·L^-1) → α-quartz (≥5 mol·L^-1). Simultaneously, relative density increased from 71% (no solvent) to 95.7% (10 mol·L^-1 NaOH). SEM revealed that strong alkalinity produced well-defined grain boundaries and uniform microstructures, while weak or neutral conditions resulted in porous, poorly bonded networks.

The phase transition was also sensitive to sintering temperature and pressure. At 200 ℃, no crystallization occurred even at 600 MPa. Crystallization initiated at 250 ℃ and 300 MPa, and complete α-quartz formation occurred at ≥300 ℃ and ≥400 MPa. Increasing pressure facilitated particle rearrangement, pore elimination, and enhanced atomic diffusion at the interface, accelerating phase transition. A comprehensive temperature-pressure-phase diagram was established, clearly delineating the non-crystalline, partially crystalline, and fully crystalline regions.

Mechanical properties were strongly correlated with microstructure and phase composition. The α-quartz ceramics cold-sintered with 5 mol·L^-1 NaOH exhibited a Vickers hardness of 5.1 GPa, Young's modulus of 67.8 GPa, fracture toughness of 0.98 MPa·m^1/2, and flexural strength of (58 ± 7) MPa. These values represent increases of 30%, 40%, and 110% in hardness, modulus, and toughness, respectively, compared to the amorphous samples. The enhanced mechanical properties are attributed to the formation of well-bonded crystalline interfaces that enable efficient stress transfer and crack deflection, unlike the disordered amorphous structure.

This work demonstrates a controllable strategy to induce amorphous-to-α-quartz transformation in low-solubility silica ceramics through the regulation of transient solvent alkalinity during cold sintering. By introducing strong alkaline NaOH solutions (≥3 mol·L^-1), the activation energy for crystallization can be significantly reduced, enabling complete transformation at 300 ℃ under 500 MPa. The critical crystallization threshold was identified at 250 ℃ and 200 MPa, and a detailed temperature-pressure-phase diagram was established to illustrate the transition pathways. The resulting ceramics achieved a relative density above 95% and exhibited excellent mechanical performance, including a Vickers hardness of 5.1 GPa, Young's modulus of 67.8 GPa, fracture toughness of 0.98 MPa·m^1/2, and flexural strength of (58 ± 7) MPa. These results clearly indicate that alkaline regulation during CSP not only enables precise control of phase structure but also produces dense, mechanically robust α-quartz ceramics at dramatically reduced sintering temperatures. This approach provides both fundamental insights and practical guidance for the low-energy fabrication of advanced low-solubility ceramic components.