The development trend of high voltage, high current and high-power density of power semiconductor devices has raised the requirement for the heat dissipation capability and reliability of ceramic substrates in devices. Silicon nitride (Si₃N₄) ceramics, known for their high thermal conductivity and excellent mechanical properties, have emerged as a preferred thermal dissipation substrate material for high-power electronic devices. However, there is a significant gap between experimental and theoretical values of thermal conductivity in Si₃N₄ ceramics. The long period of heat preservation during preparation leads to excessive grain growth, compromising mechanical properties and increasing costs, which hinders large-scale application. Lattice oxygen defects act as main factor limiting thermal conductivity of Si₃N₄ ceramics. Now, researchers are exploring ways to promote removal of lattice oxygen and full development of bimodal morphology formation of Si₃N₄, by selecting non-oxide sintering additives to reduce the oxygen content in the system, adjusting the composition and properties of the liquid phase, constructing a “nitrogen-rich-oxygen-deficient” liquid phase, and regulating the dissolution and precipitation process in the liquid phase. These efforts aim to the synergistic optimization of thermal conductivity-mechanical properties of Si₃N₄ ceramics. Based on the elemental classification, we review the non-oxide sintering additives developed at domestic and abroad, explain how they improve the thermal conductivity of Si₃N₄ ceramics from liquid-phase modulation and microscopic morphology control, analyze the grain development and morphology evolution laws, and discusse the mechanism of lattice oxygen removal. The out look on future development of high thermal conductivity Si₃N₄ ceramics is also prospected.

With the rise of the third-generation wide-bandgap semiconductors represented by SiC and GaN, power electronic devices are developing rapidly towards high output power and high power density, putting forward higher performance requirements on ceramic substrate materials used for power module packaging. The conventional Al₂O₃ and AlN ceramics are inadequate for the new generation of power module packaging applications due to low thermal conductivity or poor mechanical properties. In comparison, the newly developed Si₃N₄ ceramics have become the most potential insulating heat dissipation substrate materials due to its excellent mechanical properties and high thermal conductivity. In recent years, researchers have made a series of breakthroughs in the preparation of high strength and high thermal conductivity Si₃N₄ ceramics by screening effective sintering additive systems and optimizing the sintering processes. Meanwhile, as the advancement of the engineering application of coppered Si₃N₄ ceramic substrate, the evaluation of its mechanical, thermal, and electrical properties has become a research hotspot. Starting from the factors affecting thermal conductivity of Si₃N₄ ceramics, this article reviews the domestic and international research work focused on sintering aids selection and sintering processes improvement to enhance the thermal conductivity of Si₃N₄ ceramics. In addition, the latest progress in the dielectric breakdown strength of Si₃N₄ ceramic substrates and the evaluation of properties after being coppered are also systematically summarized and introduced. Based on above progresses and faced challengies, the future development direction of high strength and high thermal conductivity Si₃N₄ ceramic substrates is prospected.

AlN-SiC multiphase ceramics possess robust mechanical strength, high thermal conductivity and good oxidization resistance, and show great potential as the matrix material of fiber reinforced ceramic matrix composites. In this work, AlN-SiC multiphase ceramics were fabricated via low temperature reactive melt infiltration of Si-Al alloy into porous C-Si₃N₄ preforms. Influence of Si-Al source on the melt infiltration process was studied, and impact of residual silicon on the mechanical and thermal properties of the AlN-SiC ceramics was investigated. It was found that an Al-O layer was in-situ formed at the interface between Si-Al melt and C-Si₃N₄ preform, when Si-Al powder was used as the infiltration medium. This seriously retarded the melt infiltration process and made the penetration of Si-Al melt into the C-Si₃N₄ preform hardly possible. However, when Si-Al ingot was used as the infiltration medium, a well infiltration of Si-Al melt into the C-Si₃N₄ preform occurred, which led to the formation of dense AlN-SiC ceramics. Mechanical and thermal property measurements indicated that the strength of the AlN-SiC ceramics was significantly improved as the residual silicon content in it was reduced, while a reverse trend was observed for the thermal conductivity. AlN-SiC ceramics with 4%(in mass) residual silicon showed a high strength of 320.1 MPa, nearly comparable to that of conventional reaction bonded SiC, although its thermal conductivity was modest (26.3 W·m^-1·K^-1). The fundamental reasons for the above phenomena were discussed. This study is of great significance for the preparation of SiC_f/AlN-SiC composites by low temperature reactive melt infiltration.

To expand the utilization of iron tailings, four kinds of porous ceramics were prepared by foam gel-casting with pressureless sintering, foam gel-casting with reactive sintering, and mold forming with reactive sintering using fine-grained high-silicon iron tailings, iron tailings + graphite, and iron tailings + graphite + silicon carbide as raw materials, respectively. DSC-TG and XRD analysis was applied to investigate the sintering process of iron tailings and the carbothermal-reduction reaction between iron tailings and graphite. The four porous ceramics’ porosities, compressive strengths, and thermal conductivities were further analyzed. The results show that the porous ceramics made only from iron tailings possesses high porosity (87.2%), compressive strength (1.37 MPa), and low thermal conductivity (0.036 W/(m·K)), meeting the requirement of thermal insulation material. Silicon carbide porous ceramics with improved thermal conductivity but a slight sacrifice of strength can be fabricated through carbothermal reduction between iron tailings and graphite. Moreover, the compressive strength of silicon carbide porous ceramics can be significantly increased by adding some silicon carbide to the raw materials. The silicon carbide porous ceramics achieved high porosity of 91.6%, high compressive strength of 1.19 MPa and thermal conductivity of 0.31 W/(m·K), which can be a guarantee of a carrier for composite phase change materials or light thermal conductive materials. Compared with foam gel-casting, the mold-forming process can significantly improve the thermal conductivity (1.15 W/(m·K)) of silicon carbide porous ceramics and greatly reduce the cost of raw materials and manufacturing, which is profitable for industrialization.

Silicon carbide ceramic matrix composites have been widely used in aerospace, friction brake, fusion fields and so on, and become advanced high-temperature structural and functional composites, due to their high specific strength and specific modulus, excellent ablation and oxidation resistance, and high conductivity and good thermal shock resistance. This paper reviews the latest research progress in preparation and property of silicon carbide ceramics matrix composites (CMCs) with high thermal conductivity. Researchers have improved the thermal conductivity of silicon carbide CMCs, including by introducing highly thermal conductive phases for reinforcing heat transport, such as diamond powders, and mesophase pitch-based carbon fibers (MPCF), by optimizing the interface between pyrolytic carbon (PyC) and silicon carbide matrix for reducing interfacial thermal resistance, by heat-treating for obtaining silicon carbide matrix with higher crystallinity and better thermal conductivity, and by designing preform structure for establishing continuous thermal conduction path. Meanwhile, research interests on silicon carbide CMCs are to explore new preparation with high efficiency and low cost through optimising their influencing factors, and to obtain isotropic highly thermal conductivity with dimensional stability and physical properties through deep understanding their thermal conductive mechanism, and flexible method based on the structure-activity relationship.