Nd2Zr2O7烧绿石A、B位晶格固化钍的结构演化及化学稳定性研究

doi:10.15541/jim20220077

无机材料学报 ›› 2022, Vol. 37 ›› Issue (10): 1073-1078.DOI: 10.15541/jim20220077 CSTR: 32189.14.10.15541/jim20220077

Nd₂Zr₂O₇烧绿石A、B位晶格固化钍的结构演化及化学稳定性研究

王烈林(), 谢华, 谢宇骐, 胡平涛, 尹雯, 任馨玥, 丁芸

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

收稿日期:2022-02-16 修回日期:2022-03-23 出版日期:2022-10-20 网络出版日期:2022-04-07
作者简介:王烈林(1982-), 男, 博士, 副研究员. E-mail: wanglielin@swust.edu.cn
基金资助:
国家自然科学基金(21101129);国家自然科学基金(41502028);四川省自然科学基金项目(2018jy0449);四川省自然科学基金项目(2022NSFSC0252)

Structural Evolution and Chemical Durability of Thorium-incorporated Nd₂Zr₂O₇ Pyrochlore at A and B Sites

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

Received:2022-02-16 Revised:2022-03-23 Published:2022-10-20 Online:2022-04-07
About author:WANG Lielin (1982-), male, PhD, associate professor. E-mail: wanglielin@swust.edu.cn
Supported by:
National Natural Science Foundation of China(21101129);National Natural Science Foundation of China(41502028);Natural Science Foundation of Sichuan Province(2018jy0449);Natural Science Foundation of Sichuan Province(2022NSFSC0252)

摘要/Abstract

摘要：

A₂B₂O₇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Nd₂Zr₂O₇烧绿石A、B位钍掺杂Nd_1.8Th_0.2Zr₂O₇和Nd₂Zr_1.8Th_0.2O₇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。Nd₂Zr₂O₇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AO₈六面体结构扭曲, B位掺杂导致BO₆八面体部分形变。Nd_1.8Th_0.2 Zr₂O₇和Nd₂Zr_1.8Th_0.2O₇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Nd₂Zr₂O₇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。

关键词: 烧绿石, 钍, 结构演化, 化学稳定性, A位掺杂, B位掺杂

Abstract:

A₂B₂O₇ pyrochlore is considered as a candidate host matrix for high-level radioactive wastes due to its incorporation and physicochemical stability. Nd_1.8Th_0.2Zr₂O₇ and Nd₂Zr_1.8Th_0.2O₇ 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_1.8Th_0.2Zr₂O₇and Nd₂Zr_1.8Th_0.2O₇exhibit pure single pyrochlore structure. Rietveld refinement analyses show that the value of 48f oxygen site parameter of 20% thorium-doped Nd₂Zr₂O₇pyrochlore increases, which suggests that the structure is transforming from ordered pyrochlore to disordered structure, as compared with Nd₂Zr₂O₇. The Nd_1.8Th_0.2Zr₂O₇ pyrochlore structure evolution results from the distortion of the AO₈hexahedral structure, while the B-site substitution leads to partial deformation of the BO₆octahedron. The leaching experiment results show that the normalized leaching rate of thorium is as low as 10^-5g·m^-2·d^-1 after 42 d. Thorium can be well incorporated at the A and B cation sites of the Nd₂Zr₂O₇ pyrochlore structure of which the immobilization exhibits the excellent physical and chemical properties.

Key words: pyrochlore, thorium, structural evolution, chemical durability, A-site substitution, B-site substitution

中图分类号:

TQ174

王烈林, 谢华, 谢宇骐, 胡平涛, 尹雯, 任馨玥, 丁芸. Nd₂Zr₂O₇烧绿石A、B位晶格固化钍的结构演化及化学稳定性研究[J]. 无机材料学报, 2022, 37(10): 1073-1078.

WANG Lielin, XIE Hua, XIE Yuqi, HU Pingtao, YIN Wen, REN Xinyue, DING Yun. Structural Evolution and Chemical Durability of Thorium-incorporated Nd₂Zr₂O₇ Pyrochlore at A and B Sites[J]. Journal of Inorganic Materials, 2022, 37(10): 1073-1078.

图/表 8

图1 样品Nd1.8Th0.2Zr2O7、Nd2Zr2O7和Nd2Zr1.8Th0.2O7的XRD图谱

Fig. 1 XRD patterns of samples Nd1.8Th0.2 Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

图2 样品Nd1.8Th0.2 Zr2O7、Nd2Zr2O7和Nd2Zr1.8Th0.2O7的SEM照片及EDS元素分布图

Fig. 2 SEM images and EDS elements mappings of samples Nd1.8Th0.2 Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

图3 样品Nd1.8Th0.2 Zr2O7、Nd2Zr2O7和Nd2Zr1.8Th0.2O7 的XRD结构精修分析

Fig. 3 Rietveld refinement patterns of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

表1 样品Nd1.8Th0.2 Zr2O7、Nd2Zr2O7和Nd2Zr1.8Th0.2O7的Rietveld精修数据

Table 1 Rietveld refinement parameters of samples Nd1.8Th0.2 Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

	Nd_1.8Th_0.2Zr₂O₇	Nd₂Zr₂O₇	Nd₂Zr_1.8Th_0.2O₇
Lattice parameter/nm	1.06370(2)	1.06744(5)	1.06781(4)
Unit cell volume/nm³	1.203	1.216	1.217
x-parameter of 48f oxygen	0.3322(6)	0.3287(6)	0.3365(5)
A-O_48f bond distance	2.5932(5)	2.6285(4)	2.5713(4)
B-O_48f bond distance	2.0737(3)	2.0660(2)	2.1017(2)
A-B bond distance	3.7607(4)	3.7739(1)	3.7753(2)
A-8a bond distance	2.3029(2)	2.3110(1)	2.3118(3)
R_p	4.66%	5.17%	4.43%
R_wp	6.04%	6.79%	5.94%
χ²	2.614	1.932	2.237

图4 样品Nd1.8Th0.2 Zr2O7、Nd2Zr2O7和Nd2Zr1.8Th0.2O7的晶体结构变化

Fig. 4 Structural evolution of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

图5 样品Nd1.8Th0.2Zr2O7、Nd2Zr2O7和Nd2Zr1.8Th0.2O7的Raman图谱

Fig. 5 Raman spectra of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7

图6 样品Nd1.8Th0.2Zr2O7、Nd2Zr2O7和Nd2Zr1.8Th0.2O7的Raman峰强度变化

Fig. 6 Raman peak intensity variation of samples Nd1.8Th0.2Zr2O7, Nd2Zr2O7 and Nd2Zr1.8Th0.2O7 The peak intensity is normalized to the intensity of 299 cm-1

图7 样品Nd1.8Th0.2Zr2O7和Nd2Zr1.8Th0.2O7 Th的归一化浸出率

Fig. 7 Normalized release rates of Th in samples Nd1.8Th0.2Zr2O7 and Nd2Zr1.8Th0.2O7

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Nd₂Zr₂O₇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 Nd₂Zr₂O₇ Pyrochlore at A and B Sites

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