Microwave composite substrate is one of functional composite materials composing of polymer and inorganic fillers, which is used in microwave band circuits for signal transmission, electrical connections, and supporting components. Microwave composite substrate is a fundamental, common and key material in aerospace, electronic countermeasure, 5G/6G communication and other fields. In the past two decades, the domestic development of microwave composite substrate has made a great progress, but it is still a challenge. This review represented the properties of a microwave composite substrate and elaborated the factors influencing the properties and the functional mechanism. Also, the properties of different microwave composite substrates were discussed according to the category of polymer matrix. The domestic and international research studies on the microwave composite substrates in the past decade was further described. In addition, the development of domestic microwave composite substrate was also prospected to provide some references for improving its manufacture.

With the development of 5G communication technology and the widespread commercial use of the third-generation wide bandgap semiconductors, the power electronic devices with higher frequency, miniaturization and higher energy efficiency become popular. MnZn ferrite as a high-frequency soft magnetic materials of power electronic devices has attracted attention recently. This review introduced the latest research progress on high frequency MnZn ferrites, including the realization of characteristics of high frequency, wide temperature and low loss through the main component design, additive regulation and low temperature sintering process. This review also represented the stress sensitivity of power loss in the high frequency MnZn ferrite. Somefurther researches on the mechanism of high frequency power loss could accelerate the development and application of low core loss high-frequency MnZn ferrite in this decade.

Solid oxide fuel cell (SOFC) is an energy conversion device that converts chemical energy stored in fuel and oxidizer into electrical energy. Since SOFC has some advantages of high efficiency, low product clean pollution and low noise, it thus becomes a hot research topic in recent years. The perovskite type of mixed electron-ion conductor is extensively investigated as a SOFC electrode material. In this paper, PrFe_0.7Ni_0.3O_3-δ (PFN) with an orthorhombic structure was synthesized by a solid-phase method. The results show that the conductivity values are 46.500 and 0.007 S/cm in air and in H₂, respectively, when PFN is at 800 ℃. The interfacial polarization impedance values are 0.08 and 0.24 Ω·cm² in air and H₂, respectively. The maximum power densities of the PFN/LSGM/PFN symmetric cell are 475 and 180 mW/cm² at 800 ℃ when using hydrogen or ethanol as a fuel, respectively. It is indicated that Ni-doped PrFeO₃ is a promising SOFC electrode material with the superior performance.

Microwave dielectric ceramics are the key basic materials of 5G/6G communication technology, and the materials with a high quality factor (Q×f), a low dielectric constant (ε_r) and a near-zero temperature coefficient of resonant frequency (τ_f) become a focus of research and development. In this paper, a series of garnet Ca_3-xMg_xYb₂Ge₃O₁₂ (0≤x≤3) ceramics were prepared by a solid-state reaction approach, and the influence of Mg²⁺ "rattling" effects in the A-site on the microwave dielectric properties was investigated. The ceramics with 0≤x≤2 exhibit a normal garnet structure, ε_r gradually increases from 10.3 to 11.8, whereas the Q×f gradually decreases from 98 000 GHz to 78 000 GHz, and τ_f is in the range from -40×10^-6 to -56×10^-6/℃. The ceramics with 2<x≤3 have an inverse garnet structure with Mg²⁺ in the A-site and ε_r quickly increases to 13.5, whereas the Q×f apparently decreases to 19, 800 GHz, and the τ_f value varies from the negative value to the positive value (+70.5×10^-6/℃), which are attributed to the rattling effect Mg²⁺ and the mismatch between Mg²⁺ and Yb³⁺ in the A-site. According to the extrapolated values of the far-infrared reflective spectrum in the microwave region, the intrinsic ε_r and Q×f values are in a reasonable agreement with the measured values.

Ceramic materials for microwave systems often show versatile profiles, such as cylindrical and cubic shapes with centimeter sizes. The measurement of such samples thus becomes a challenge. In this paper, a dual-band dielectric sensor based on the complementary split-ring resonators was developed, and a measurement method to characterize the samples with different shapes and sizes was proposed. The resonator creates two operation frequency ranges, which are in wireless communication bands. In each range, numerical simulation was conducted to build the fitting models for each sample. The measurement was conducted to verify the numerical models and the measurement accuracy. The results indicate that the measured accuracy can be as high as 3.5%. Such a measurement method in association with the proposed sensor is competent for dielectric measurement for ceramic of versatile profile, indicating a sample adaptive capability. The novelty of this work lies in its capability of measurement of various samples in a centimeter scale without modifying either the sensor or the material under test (MUT). In addition, a dual-band operation is also a feature of this work, and the discrepancy between the two bands is less than 5%.

Amorphous carbon materials exhibit more advantages in mechanical, optical and thermal properties with the increasing concentration of sp³-hybridized bonds. High pressure, as an extreme physical condition, can effectively trigger sp² to sp³ bonding conversion in carbon materials. In this review, some recent achievements and progress on the synthesis of new superhard amorphous carbon materials under high pressure were introduced, mainly including the studies on the transformation of fullerene and glassy carbon into sp³ amorphous carbon material under high pressure and high temperature or high pressure with shear stress. These results deepen our understanding on the structural transition of covalently bonded amorphous materials and the relation between their microstructure and properties. Based on this, we also hold out some prospect for the future study of new superhard sp³ amorphous carbon materials under extreme conditions.

To meet the requirements of high-frequency wireless communication, microwave dielectric ceramics of (1-x)MgNb₂O₆-xCaTiO₃ (x=0, 0.02, 0.04, 0.08, 0.12, and 0.16) with a near-zero temperature coefficient were prepared by a solid-state method. The effect of CaTiO₃ addition on the microstructure and dielectric properties of MgNb₂O₆ was investigated, and the formation and sintering behavior of each phase were analyzed. The results show that a proper addition of CaTiO₃ can promote the sintering of MgNb₂O₆ and reduce its sintering temperature. Based on the X-ray diffraction analysis, CaTiO₃ can react with MgNb₂O₆ to form CaNb₂O₆, Ti₈O₁₅, and Ti₂Nb₁₀O₂₉ at a high temperature. Increasing the proportion of CaTiO₃ reduces the quality factor Q×f, but increases the dielectric constant ε_r and frequency temperature coefficient τ_f. When the addition amount (x) of CaTiO₃ is 0.16, the sample has the optimum microwave dielectric properties after sintering at 1 250 ℃ for 4 h (i.e., ε_r=21.6, Q×f =86 601 GHz, and _{τf =} -₇.3×10^-6/℃).

Data-driven methods including machine learning are widely used in materials properties prediction and devices design due to their abilities to discover the underlying statistical correlations from data, achieve target prediction efficiently and accurately, and assist in the analysis of physical images behind the data. In recent years, machine learning modeling in the research of dielectric ceramics and devices becomes popular. Recent development on the research of machine learning prediction models for key properties (i.e., dielectric constant and quality factor of microwave dielectric ceramics) was represented. Machine learning methods in dimensional optimization, failure analysis, etc. for antennas and filters were also introduced. In addition, some prospects of data-driven studies in materials and devices were also provided.

Microwave dielectric ceramics are widely used as dielectric materials in passive devices of the internet of things, industrial internet, 5G communications, and global satellite communication systems. This review introduced the densify mechanism and process parameters of cold sintering process. The main material systems and devices of cold sintered microwave dielectric ceramics were summarized. The main challenges and prospections of cold sintered microwave dielectric ceramics were pointed out. Cold sintering process has some advantages of low sintering temperature (<300 ℃), co-firing heterogeneous materials, small grain size difference before and after sintering, simple preparation process, energy saving and environmental protection, etc., which has potential applications in multi-layer co-fired ceramics and microwave system integration.

The control of pollutants has attracted considerable recent attention. The removal technology of antibiotics as pollutants becomes a challenge, especially water treatment technology based on photocatalytic degradation of antibiotics. In this paper, WO₃ was prepared by a hydrothermal method, and the S-scheme heterojunction BiOBr/WO₃ was constructed by a precipitation method at room temperature. Compared with BiOBr and WO₃, the formation of S-scheme heterojunction improves the photocatalytic activity, and reduces the recombination rate of photogenerated electron-hole pairs. The optimum photocatalytic performance of BiOBr/WO₃ with a mass fraction of 20% can be achieved, and the degradation rate for ciprofloxacin (CIP) is 94.93% within 120 min. Based on the electron spin resonance and radical trapping experiments, ·O₂^- is a primary active component in the photocatalytic degradation of CIP. The results of high-performance liquid chromatography-mass spectrometer system indicate that six intermediates are produced during the degradation of CIP, which are eventually mineralized into CO₂, H₂O and other inorganic ions.