Synthesis, characterization and dielectric properties of new unidimensional quaternary tellurites: LaTeNbO6, LaTe6M2O23, and La4Te6Ta2O23

摘要

Three new tellurites, LaTeNbO6 and La4Te6M2O23 (M = Nb or Ta) have been synthesized, as bulk phase powders and crystals, by using La2O3, Nb2O5 (or Ta2O5), and TeO2 as reagents. The structures of LaTeNbO6 and La4Te6Ta2O23 were determined by single crystal X-ray diffraction. LaTeNbO6 consists of one-dimensional corner-linked chains of NbO6 octahedra that are connected by TeO3 polyhedra. La4Te6M2O23 (M = Nb or Ta) is composed of corner-linked chains Of MO6 octahedra that are also connected by TeO4 and two TeO3 polyhedra. In all of the reported materials, Te4+ is in an asymmetric coordination environment attributable to its stereo-active lone-pair. Infrared, thermogravimetric, and dielectric analyses are also presented. Crystallographic information: LaTeNbO6, triclinic, space group P - 1, a = 6.7842(6) Angstrom, b = 7.4473(6) Angstrom, c = 10.7519(9) Angstrom, alpha = 79.6490(10)degrees, beta = 76.920(2)degrees, gamma = 89.923(2)degrees, Z = 4; La4Te6Ta2O23, monoclinic, space group C2/c, a = 23.4676(17) Angstrom, b = 12.1291(9) Angstrom, c = 7.6416(6) Angstrom, beta = 101.2580(10)degrees, Z = 4. (C) 2003 Elsevier Inc. All rights reserved. [References: 19]