混合金属碲酸盐：Na1.4Nb3Te4.9O18和NaNb3Te4O16的合成、结构与表征

Mixed-metal tellurites: synthesis, structure, and characterization of Na1.4Nb3Te4.9O18 and NaNb3Te4O16.

作者信息

Ok Kang Min, Halasyamani P Shiv

机构信息

Department of Chemistry and Center for Materials Chemistry, 136 Fleming Building, University of Houston, Houston, Texas 77204-5003, USA.

出版信息

Inorg Chem. 2005 May 30;44(11):3919-25. doi: 10.1021/ic050256b.

DOI:10.1021/ic050256b

PMID:15907119

Abstract

Two new mixed-metal tellurites, Na1.4Nb3Te4.9O18 and NaNb3Te4O16, have been synthesized by standard solid-state techniques using Na2CO3, Nb2O5, and TeO2 as reagents. The structures of Na1.4Nb3Te4.9O18 and NaNb3Te4O16 were determined by single-crystal X-ray diffraction. Both of the materials exhibit three-dimensional structures composed of NbO6 octahedra, TeO4, and TeO3 polyhedra. The Nb5+ and Te4+ cations are in asymmetric coordination environments attributable to second-order Jahn-Teller (SOJT) effects. The Nb5+ cations undergo an intraoctahedral distortion toward a corner (local C4 direction), whereas the Te4+ cations are in distorted environments owing to their nonbonded electron pair. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dielectric measurements were also performed on the reported materials. Crystal data: Na1.4Nb3Te4.9O18, monoclinic, space group C2/m (No. 12), with a = 32.377(5) A, b = 7.4541(11) A, c = 6.5649(9) A, beta = 95.636(5) degrees, V = 1576.7(4) A3, and Z = 4; NaNb3Te4O16, monoclinic, space group P2(1)/m (No. 11), with a = 6.6126(13) A, b = 7.4738(15) A, c = 14.034(3) A, beta = 102.98(3) degrees, V = 675.9(3) A3, and Z = 2.

摘要

通过标准固态技术，以碳酸钠、五氧化二铌和二氧化碲为试剂，合成了两种新型混合金属碲酸盐，即Na1.4Nb3Te4.9O18和NaNb3Te4O16。通过单晶X射线衍射确定了Na1.4Nb3Te4.9O18和NaNb3Te4O16的结构。这两种材料均呈现出由NbO6八面体、TeO4和TeO3多面体组成的三维结构。Nb5+和Te4+阳离子处于归因于二阶 Jahn-Teller（SOJT）效应的不对称配位环境中。Nb5+阳离子在八面体内朝着一个角（局部C4方向）发生畸变，而Te4+阳离子由于其非键电子对而处于畸变环境中。还对所报道的材料进行了红外和拉曼光谱、紫外-可见漫反射光谱、热重分析和介电测量。晶体数据：Na1.4Nb3Te4.9O18，单斜晶系，空间群C2/m（编号12），a = 32.377(5) Å，b = 7.4541(11) Å，c = 6.5649(9) Å，β = 95.636(5)°，V = 1576.7(4) Å3，Z = 4；NaNb3Te4O16，单斜晶系，空间群P2(1)/m（编号11），a = 6.6126(13) Å，b = 7.4738(15) Å，c = 14.034(3) Å，β = 102.98(3)°，V = 675.9(3) Å3，Z = 2。