Effect of phase transformation on the densification of LaYO₃ pellet

Fabrication process of LaYO₃ pellets was studied to develop a reaction-preventing material for casting metallic nuclear fuel. LaYO₃ pellets were fabricated by sintering La₂O₃ and Y₂O₃ powders. Phase transformation and densification behavior of the LaYO₃ were investigated at various temperatures to find optimal conditions of LaYO₃ sintering process. Two different LaYO₃ structures were formed depending on sintering temperature; an orthorhombic perovskite LaYO₃ structure was formed at the sintering temperatures of 1633, 1703, 1743, 1763, 1773, and 1793 K, while a monoclinic LaYO₃ structure was formed at a sintering temperature of 1843 K. The Bulk density of sintered LaYO₃ pellets increased up to 1763 K, and decreased at the temperatures ranging from 1763 to 1843 K. This study demonstrated that the formation of the LaYO₃ phases and the density of the LaYO₃ sintered pellets were regulated by varying the sintering temperature. Thus, the fabrication temperature of the high-density LaYO₃ sintered pellets was optimized, and the mechanism of the change in density was elucidated.