Abstract: Yttrium hydride (YH_x) has recently attracted considerable attention as a highly promising candidate for the development of compact reactors. This is primarily attributed to its exceptional thermal stability and superior hydrogen storage capacity, which are particularly advantageous under high-temperature conditions. YH_x samples were fabricated by spark plasma sintering (SPS) with systematically varied process parameters. Results reveal that the microstructure of sintered YH_x exhibits significant variations under different sintering processes. SPS process promotes the densification of sintered YH_x monoliths, and the co-evolution of microstructure and grain growth behavior optimizes phonon transport pathways, thereby enhancing the thermal conductivity. The thermal conductivity of sintered YH_x decreases with increasing temperature. Optimized under the conditions of 1000 °C/65 MPa/5 min, the sintered YH_x achieved a relative density of 99.14% and hydrogen content of 1.91 wt.%, exhibiting a maximum thermal conductivity of 67.8 W/(m K) at 300 K. This study conducted an in-depth analysis of the mechanisms influencing thermal conductivity variations and established more comprehensive sintering process-microstructure-thermal conductivity relationships for YH_x.

Key words: Yttrium hydride, Spark plasma sintering, Microstructure evolution, Thermal conductivity