LaYO₃ which has phase stability at high temperature is introduced as a promising candidate for reaction-preventing crucible materials with Uranium-Zirconium (U-Zr) melt containing rare-earth elements (RE). RE is composed of rare-earth elements such as Nd, Ce, Pr and La. The LaYO₃ material was synthesized by a solid-state reaction method at elevated temperature according to a pseudo-phase diagram of LaYO₃ and Y₂O₃. Green compacts blended with La₂O₃ and Y₂O₃ powder were made by the Cold Isostatic Pressing (CIP) method, with La₂O₃ and Y_{2O3 powders varying with molar ratios from 1.0 to 1:2. LaYO3 synthetics were fabricated at sintering temperatures ranging from 1450°C to 1600°C. LaYO3 pellets sintered at below 1550°C showed a highly dense orthorhombic phase with a perovskite structure, resulting in an enhancing reaction-resistant effect with RE.}