Nd_(2)Zr_(2)O_(7)烧绿石A、B位晶格固化钍的结构演化及化学稳定性研究  

Structural Evolution and Chemical Durability of Thorium-incorporated Nd_(2)Zr_(2)O_(7) Pyrochlore at A and B Sites

作　　者：王烈林[1] 谢华[1] 谢宇骐 胡平涛 尹雯 任馨玥 丁芸 WANG Lielin;XIE Hua;XIE Yuqi;HU Pingtao;YIN Wen;REN Xinyue;DING Yun(Fundamental Science on Nuclear Wastes and Environmental Safety Laboratory,Southwest University of Science and Technology,Mianyang 621010,China)

机构地区：[1]西南科技大学核废物与环境安全国防重点学科实验室,绵阳621010

出　　处：《无机材料学报》2022年第10期1073-1078,共6页Journal of Inorganic Materials

基　　金：国家自然科学基金(21101129,41502028);四川省自然科学基金(2018jy0449,2022NSFSC0252)。

摘　　要：A_(2)B_(2)O_(7)烧绿石以其高包容性和物理化学稳定性而成为高放废物固化体候选基材。研究通过喷雾热解-高温烧结制备了Nd_(2)Zr_(2)O_(7)烧绿石A、B位钍掺杂Nd_(1.8)Th_(0.2)Zr_(2)O_(7)和Nd_(2)Zr_(1.8)Th_(0.2)O_(7)固化体,利用不同检测手段分析样品结构,并通过MCC-1方法研究了样品化学稳定性。Nd_(2)Zr_(2)O_(7)烧绿石A和B位掺杂Th均能形成纯烧绿石结构,掺杂将造成烧绿石结构中48f氧位置参数增大,烧绿石向无序化结构转变。A位掺杂导致烧绿石AO_(8)六面体结构扭曲,B位掺杂导致BO_(6)八面体部分形变。Nd_(1.8)Th_(0.2)Zr_(2)O_(7)和Nd_(2)Zr_(1.8)Th_(0.2)O_(7)固化体在42 d周期后Th离子浸出率在10^(-5) g·m^(-2)·d^(-1)量级,说明锕系核素Th在Nd_(2)Zr_(2)O_(7)的A、B位均能很好地被包容,固化体表现出优异的物理化学性能。A_(2)B_(2)O_(7) pyrochlore is considered as a candidate host matrix for high-level radioactive wastes due to its incorporation and physicochemical stability.Nd_(1.8)Th_(0.2)Zr_(2)O_(7) and Nd_(2)Zr_(1.8)Th_(0.2)O_(7) pyrochlore samples doped with 20% thorium(in molar)were successfully prepared by using spray-pyrolysis and high temperature sintering method.The structures of the synthesized immobilization were characterized,and the chemical durability tests were investigated by the MCC-1 method.Structural analyses show that samples Nd_(1.8)Th_(0.2)Zr_(2)O_(7) and Nd_(2)Zr_(1.8)Th_(0.2)O_(7) exhibit pure single pyrochlore structure.Rietveld refinement analyses show that the value of 48f oxygen site parameter of 20% thorium-doped Nd_(2)Zr_(2)O_(7) pyrochlore increases,which suggests that the structure is transforming from ordered pyrochlore to disordered structure,as compared with Nd_(2)Zr_(2)O_(7).The Nd_(1.8)Th_(0.2)Zr_(2)O_(7) pyrochlore structure evolution results from the distortion of the AO_(8) hexahedral structure,while the B-site substitution leads to partial deformation of the BO_(6) octahedron.The leaching experiment results show that the normalized leaching rate of thorium is as low as 10^(-5)g·m^(-2)·d^(-1) after 42 d.Thorium can be well incorporated at the A and B cation sites of the Nd_(2)Zr_(2)O_(7) pyrochlore structure of which the immobilization exhibits the excellent physical and chemical properties.

关 键 词：烧绿石 钍 结构演化 化学稳定性 A位掺杂 B位掺杂 

分 类 号：TQ174[化学工程—陶瓷工业]