Synthesis and Characterization of Thorium-doped Nd2Zr2O7 Pyrochlore

A(2)Zr(2)O(7) zirconate pyrochlores are proposed as potential host phases for the immobilization of high level nuclear waste because of their chemical and radiation stabilities. Thorium-doped pyrochlore Nd1.8Th0.2Zr2O7.1 was synthesized at 1200 degrees C for 12 h by citrate polymer precursor method using zirconium nitrate, thorium nitrate, neodymium nitrate and citrate acid as raw materials. The phase compositions of the products were characterized by XRD, SEM, FT-IR and Raman spectrum. The results reveal that neodymium ions are substituted by thorium ions at the A position of A(2)Zr(2)O(7), which maintain the single pyrochlore structure. The lattice parameter decreases for Nd2Zr2O7 pyrochlore with the addition of 20at% Th because the effective ionic radius of Th4+ is less than that of Nd3+. The mean grain sizes of these samples are about 50 nm and the bulk densities are more than 95% of theoretical values. With thorium content increase, the degree of structural disorder in Nd1.8Th0.2Zr2O7.1 pyrochlore increases.