Ca1-xSrxZr4（PO4）6磷酸盐陶瓷固化体的制备及化学稳定性

Preparation and Chemical Stability of Ca1-xSrxZr4（PO4）6 Phosphate Ceramics Solidified Waste

为研究磷酸锆钙(CaZr4(PO4)6,简称CZP)对放射性核素90Sr的固化能力,采用88Sr作为90Sr的模拟替代物,以Ca(NO3)2·4H2O、Sr(NO3)2、Zr(NO3)4·5H2O、NH4H2PO4为原料,采用固相烧结工艺制备了Ca1-xSrxZr4(PO4)6磷酸盐陶瓷固化体。系统研究了Sr掺量对固化体物相组成、微观结构、致密性的影响。XRD结果表明:随着Sr^2+掺量的增加,固化体的物相组成从CZP逐渐变为SrZr4(PO4)6(SZP)。密度测试结果表明:掺Sr^2+的CZP固化体具有良好的致密性,且密度随着Sr^2+掺量的增加而增大。SEM-EDX结果表明:固化体微观形貌致密且固化体中各基体元素均匀分布。此外,采用PCT静态浸出法研究了固化体的化学稳定性。PCT测试结果表明:Sr元素的归一化浸出率处于10^-4~10^-3 g m^-2d^-1范围,具有比Ca元素更好的抗浸出性,说明CZP陶瓷固化Sr具有很好的化学稳定性。

In order to investigate the curing ability of calcium zirconium phosphate(CaZr4(PO4)6,abbreviated as CZP)for radionuclide 90Sr,88Sr was used as surrogate for 90Sr.Ca(NO3)2·4H2O,Sr(NO3)2,Zr(NO3)4·5H2O,NH4H2PO4 were chosen as raw materials to prepare Ca1-xSrxZr4(PO4)6 phosphate ceramics by solid state reaction method.The influences of Sr doping content on the phase composition,microstructure and densification of the waste forms were systematically studied.The XRD results showed that the phase composition of the waste forms gradually changed from CZP to SrZr4(PO4)6(SZP)with the increase of Sr^2+doping amount.The density results suggested that the Sr^2+doped CZP waste forms presented better densification and the density increased with increasing Sr^2+content.The SEM-EDX results revealed that the waste forms exhibited the dense microstructure and the matrix elements in the waste forms were evenly distributed.Besides,the chemical stability of the waste forms was evaluated by PCT static leaching method.It was found that the normalized leaching rate of Sr element was in the range of 10^-4~10^-3 g m^-2d^-1,which showed the better leaching resistance than Ca element.It was indicated that the CZP ceramics for immobilizing Sr had good chemical stability.