锆基烧绿石Nd_2Zr_2O_7固化锕系核素钍

Synthesis and Characterization of Thorium-doped Nd_2Zr_2O_7 Pyrochlore

A2Zr2O7锆基烧绿石因优异的辐照和化学稳定性能成为高放废物固化的理想基材。以硝酸锆、硝酸钕、硝酸钍作为原料,通过柠檬酸络合方法,在1200℃保温12 h成功制备了含20at%钍的Nd1.8Th0.2Zr2O7.1烧绿石固化体。产物采用X射线粉末衍射、扫描电镜、红外光谱以及拉曼光谱表征。结果表明:Th替代Nd进入A2Zr2O7的A位,Nd1.8Th0.2Zr2O7.1固化体保持单一的烧绿石结构;Th4+的离子半径小于Nd3+,导致固化体晶格常数减小;通过Scherrer公式计算和SEM观察,样品平均粒径为50 nm左右;制备的固化体致密度高。随着Th成分的增加,Nd1.8Th0.2Zr2O7.1固化体烧绿石结构的无序化程度增加。

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 Ndl.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 NdEZr2O7 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 Nd1.8Th0.2ZrEO7.1 pyrochlore increases.