Thermal Conductivity of YAG:Nd + Mo Ceramic Composites Obtained by Spark Plasma Sintering

The microstructure and thermophysical properties (specific heat capacity, thermal diffusivity, thermal conductivity) of fine-grained ceramic composites based on yttrium-aluminum garnet Y_2.5Nd_0.5Al₅O₁₂ (YAG:Nd) with different molybdenum contents (10, 20 and 40 vol %) were studied. Submicron garnet powders of Y_2.5Nd_0.5Al₅O₁₂ were obtained by the coprecipitation method; YAG:Nd + Mo powder compositions with the YAG:Nd core–Mo shell structure were obtained by deposition of molybdenum onto the surface of garnet particles; samples of ceramic composites were obtained by the method of spark plasma sintering (SPS). Electron microscopy and X-ray phase analysis were used to study the microstructure and phase composition of the composites. YAG:Nd + Mo composites have a high relative density (98.1–99%) and a uniform fine-grained microstructure with a garnet grain size of 2–3 μm. Sintered YAG:Nd + Mo composites at room and elevated temperatures (up to 1100°C) have a high thermal conductivity coefficient exceeding the thermal conductivity coefficient of uranium dioxide UO₂, which allows using these materials as heat-resistant inert fuel matrices. It was shown that higher thermal conductivity of composites is ensured at a content of at least 20 vol % Mo. In composites with the addition of 20 and 40% Mo, the thermal conductivity coefficient at 1100°C reaches 7.0 and 8.8 W m^–1 K^–1, respectively.