Nd^(3+)掺杂钙钛锆石(Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2))相变行为的研究  

Study on the phase evolution of Nd^(3+)-doped zirconolite ceramics(Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2))

作　　者：提学超 李伟民 TI Xuechao;LI Weimin(School of Aircraft Manufacturing,Sichuan Aerospace Vocational College,Guanghan 618300,Sichuan,China;School of National Defense Science and Technology,Southwest University of Science and Technology,Mianyang 621000,Sichuan,China)

机构地区：[1]四川航天职业技术学院飞行器制造学院,四川广汉618300 [2]西南科技大学国防科技学院,四川绵阳621000

出　　处：《有色金属科学与工程》2024年第2期302-310,共9页Nonferrous Metals Science and Engineering

基　　金：国家863“高放废液分离、处理工艺及关键设备技术研究资助项目”(2009AA050703)。

摘　　要：为研究钙钛锆石对放射性元素Am^(3+)的稳定固化作用,以Nd^(3+)为Am^(3+)的模拟元素,系统研究了高温固相法制备Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2)时,Nd^(3+)异价取代钙钛锆石晶格中Ca^(2+)位(0≤x≤1.0)所导致的相态演变行为。合成Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2)的XRD、Raman、BSE和EDS测试结果表明:钙钛锆石(Zirconolite)晶格对Nd^(3+)离子的固溶量可达70%(x=0.7),可有效实现对Am^(3+)模拟元素Nd^(3+)离子的固化。但随着Nd^(3+)掺杂量(x≤0.3)增加,Zirconolite-2M晶格中O^(2-)和Nd^(3+)的无序化程度逐渐增加、(Ca/Nd)-O键长逐渐变小,直至(x=0.4)引起Zr^(2+)、Ti^(4+)附近的O^(2-)配位数发生改变(ZrO7→ZrO8、TiO5→TiO6),Zirconolite-2M晶格结构开始向Zirconolite-4M转变。x=0.5时,陶瓷体完全转变为Zirconolite-4M晶格且O^(2-)和Nd^(3+)有序度重新变高、Ti—O键长增加;直至x=0.6、x=0.7时,陶瓷体仍为单一Zirconolite-4M结构,但晶格中O^(2-)和Nd^(3+)的有序度又逐渐降低,以至于在x=0.7陶瓷体亚晶格中微量Ca^(2+)、Zr^(4+)、Nd^(3+)离子占位转变为烧绿石(Pyrochlore)结构。而在0.8≤x≤0.9范围内,Zirconolite-4M结构完全消失,陶瓷体为多相共存状态(Pyrochlore、ZrTiO_(4)和Nd2(TiZr)_(4)O_(11)物相)。Nd^(3+)完全取代Ca^(2+)位(x=1.0)时,陶瓷体变为单一Nd2(TiZr)_(4)O_(11)固溶体相。陶瓷体晶粒的BSE和EDS分析证实了这种相变规律。This paper used Nd^(3+)as a surrogate element of Am^(3+)to simulate the study of the stable curing effect of zirconolite on the radioactive element Am^(3+).The phase evolution behavior caused by Ca^(2+) sites in the lattice of Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2) with Nd^(3+) heterovalent substitution was systematically investigated.The Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2)(0≤x≤1.0)ceramic samples were prepared by high temperature solid-state synthesis and characterized by XRD,Raman,BSE,and EDS analysis.The experimental results showed that the solid solution content of Nd^(3+) ion could reach up to 70%(viz.x=0.7)in the zirconolite lattice.This indicated that the Nd^(3+) ion as a substitution element could effectively simulate Am^(3+)solidification in the zirconolite lattice.However,as the doping amount of Nd^(3+)(x≤0.3)increased,the disordering of the O^(2-) and Nd^(3+) ions in the zirconolite-2M lattice increased gradually.On the contrary,the(Ca/Nd)-O chemical bond was slightly shortened.Until x=0.4,the O^(2-)coordination number around some Zr^(2+)and Ti^(4+)ions changed(ZrO7→ZrO8,TiO5→TiO6),partly the zirconolite-2M structure rearrangement to the zirconolite-4M structure.When x=0.5,all the zirconolite-2M structure was converted into zirconolite-4M structure,and the ordering of the O^(2-)and Nd^(3+)cations increased again,with the Ti-O chemical bond slightly elongated.With increasing x(x=0.6、0.7),the sample still retained a single zirconolite-4M structure,but the ordering of the O^(2-) and Nd^(3+) cations gradually decreased.When x=0.7,the Ca^(2+)、Zr^(2+)、Nd^(3+) ions exhibited a subtle amount of pyrochlore structure arrangement in the sublattice.When 0.8≤x≤0.9,the samples converted to a polyphase coexistence state(Pyrochlore,ZrTiO_(4) and Nd2(TiZr)_(4)O_(11)).Finally,a single Nd2(TiZr)_(4)O_(11) solid solution phase was observed when x=1.0.Further,the composition and microstructure of coexisting phases were verified by BSE and EDS.

关 键 词：Nd^(3+)-掺杂 钙钛锆石-2M 相关系 有序-无序 

分 类 号：TL941[核科学技术—辐射防护及环境保护]