Synthesis and Characterization of Thorium-doped Nd$lt;inf$gt;2$lt;/inf$gt;Zr$lt;inf$gt;2$lt;/inf$gt;O$lt;inf$gt;7$lt;/inf$gt; Pyrochlore

Abstract

A2Zr2O7 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 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 A2Zr2O7, which maintain the single pyrochlore structure. The lat- tice parameter decreases for Nd2Zr2O7 pyrochlore with the addition of 20at% Th because the effective ionic ra- dius of Th 4+ is less than that of Nd 3+ . The mean grain sizes of these samples are about 50 nm and the bulk densi- ties are more than 95% of theoretical values. With thorium content increase, the degree of structural disorder in