CRYSTAL-STRUCTURE REFINEMENTS OF ZIRCON-TYPE MVO4 (M=SC, Y, CE, PR, ND, TB, HO, ER, TM, YB, LU)
CRYSTAL-STRUCTURE REFINEMENTS OF ZIRCON-TYPE MVO4 (M=SC, Y, CE, PR, ND, TB, HO, ER, TM, YB, LU)
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DOI：
10.1006/jssc.1994.1091
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发表时间：
1994-03-01
影响因子：
3.3
通讯作者：
BOATNER, LA
中科院分区：
文献类型：
--
作者：
CHAKOUMAKOS, BC;ABRAHAM, MM;BOATNER, LA
利用中子粉末衍射数据的全轮廓Rietveld结构分析，确定了改进的稀土原钒酸盐的结构参数(包括YVO4和ScVO4，以及PrVO4、TmVO4和LuVO4端元的新结果)。采用均相共沉淀法在熔融尿素中制备了高质量的锆英石型MVO4钒酸盐粉末。锆石结构具有空间群对称性I41/amd，Z=4，其中3个原子占据不对称单元。总共修正了22个参数，最终符合值分别为Rp=0.0313-0.0421，Rwp=0.0361-0.0511，G-of-F=1.210-1.962。所有MVO_4样品的平均V-O键长为1.709(2)ä，且V-O距离随基质尺寸的减小呈现小幅的系统性缩短。氧的位置参数、晶胞尺寸和Tm-O距离随金属离子原子序数的变化而有系统地变化。氧原子的各向异性热运动的最大幅度垂直于VO4四面体和Mo8双二面体之间的共享多面体边缘。给出了晶胞尺寸和氧原子位置随镧系离子尺寸变化的经验关系式，该关系式可用于估算其他锆英型稀土钒酸根和钒酸盐固溶体的结构参数。
Improved structural parameters for the lanthanide orthovanadates (including also YVO4and ScVO4and new results for PrVO4, TmVO4, and the LuVO4end members) have been determined by employing a full-profile Rietveld structure analysis of neutron powder-diffraction data. High-quality powders of the zircon-typeMVO4vanadates were prepared by a homogeneous coprecipitation in molten urea. The zircon structure has space group symmetryI41/amd,Z= 4, with 3 atoms occupying the asymmetric unit. In all, 22 parameters were refined with final agreement values ofRp= 0.0313-0.0421,Rwp= 0.0361-0.0511, and G-of-F = 1.210-1.962. The average V-O bond length for all of the MVO4samples is 1.709(2) Å, and the V-O distance exhibits a small systematic shortening with decreasingMatom size. The oxygen positional parameters, the cell dimensions, and theM-O distances vary systematically with the metal-ion atomic number. The anisotropic thermal motion of the oxygen atom has the largest amplitude normal to the shared polyhedral edge between the VO4tetrahedron andMO8bisdisphenoid. Empirical relations are given for the cell dimensions and oxygen atom position as a function of the size of the lanthanide ion which can be used to estimate structural parameters for other zircon-type lanthanide vanadate end-members and vanadate solid solutions.