Heat conductivity of YAG:Nd + Mo ceramic composites obtained by Spark Plasma Sintering

The microstructure and thermophysical properties (specific heat capacity, thermal conductivity coefficient, heat conductivity coefficient) of fine-grained ceramic composites based on yttrium-aluminum garnet Y2.5Nd0.5Al5O12 (YAG:Nd) with different molybdenum content (10, 20, 40 vol. %) are investigated. Submicron Y2.5Nd0.5Al5O12 powders are obtained by co-precipitation method. Powder compositions of YAG:Nd + Mo with the structure “YAG:Nd core – Mo shell” were obtained using wet chemistry techniques and precipitation of the metal phase from salt solutions. Ceramic composite samples were obtained by the Spark Plasma Sintering (SPS) method. The microstructure and phase composition of ceramics were investigated by electron microscopy and X-ray diffraction phase analysis. YAG:Nd + Mo composites have a high relative density (98.1 – 99 %) and a homogeneous fine-grained microstructure with a grain size of 2 – 3 μm. Increased thermal conductivity and heat conductivity of composites is provided with a content of at least 20 vol.% Mo. For composites with 20% and 40% Mo, the heat conductivity coefficient at 1100 °C reaches 7.0 and 8.8 W⋅m–1⋅K–1, respectively. Sintered composites YAG: Nd + Mo at room temperature and elevated temperatures (up to 1100 °C) have a high heat conductivity coefficient, exceeding the heat conductivity coefficient of uranium dioxide UO2. This makes it possible to use ceramics YAG:Nd+Mo as heat-resistant inert fuel matrices.