Synthesis, structure, and conductivity of BINBVOX ceramics

Abstract

Solid solutions based on Bi 4 V 2 O 11 , where vanadium is partially replaced by another cation (ME), form a BIMEVOX family, which is characterized by high oxy gen ionic conductivity at moderate temperatures. According to Abraham et al. [1], bismuth vanadate contains the layers of (Bi 2 O 2 ) 2+ , which alternate with the layers of (VO 3 0.5 ) 2-having anionic sublattice vacancies ( ). The Bi 4 V 2 O 11 compound undergoes a number of polymorphic transformations: α β γ. The high temperature γ modification possesses the highest conductivity. The tetragonal structure of γ Bi 4 V 2 O 11 contains three nonequivalent oxygen positions: O(1) in the layer of Bi 2 O 2 , apical position O(2), and position O(3) in the base plane of V-O polyhedrons. The structure exhibits a maximum disor der of oxygen atoms on positions O(2) and O(3) [2].A number of publications were dedicated to studies of niobium substituted bismuth vanadates. According to published data [3], the composition Bi 2 V 1 -x Nb x O 5.5 (BINBVOX) occurs in α , β , and γ modifications at 0 < x ≤ 0.075, 0.075 < x ≤ 0.15, and 0.15 < х ≤ 0.30, respectively. Steil et al. [4] Attempts at preparing a Bi 2 VO 5.5 phase and BIMEVOX (ME = Zn, Sc, Sb, In, and Pb) by mechanochemical synthesis have been made [9,10]. Diffraction patterns characteristic of the high temperature γ phase were obtained for BIMEVOX. On the contrary, a mixture of phases with the structures of fluorite and clinobisvan ite was detected in the composition of (2Bi 2 O 3 + V 2 O 5 ), which ideally corresponds to the Aurivillius phase formula Bi 2 VO 5.5 . According to Zyryanov [9], compounds with incongruent melting, including Bi 2 VO 5.5 , are not formed upon mechanical synthesis. However, Castro et al. [10] managed to stabilize γ Bi 4 V 2 O 11 by a mechanochemical activation method followed by annealing at a moderate temperature without the introduction of iso or heterovalent sub stituents into the positions of V.This work was dedicated to a study of the preparation, structure, and electrical conductivity of Bi 4 V 2 -x Nb x O 11 solid solutions. EXPERIMENTAL A standard ceramic processing in a temperature range of 770-1070 K, a coprecipitation method, and mechanochemical activation were used for the synthe sis of Abstract-The preparation and the structure and transport characteristics of Bi 4 V 2 -x Nb x O 11 (BINBVOX) were studied. A comparative analysis of the synthesis of solid solutions was performed. The sintering of ceramics and the electrical conductivity as a function of temperature, composition and partial oxygen pres sure were studied.

Role of Al and Ti doping in modulating electrical properties of BIVOX system

“…It is well known that in oxygen-ion conductor, the enhancement of ionic conductivity very well depends on the appropriate doping. Depending on the nature and concentration of suitable ME-dopant cations, the properties of parent compounds get modified; oxide ion vacancies are created, and disorder and oxygen participation in the ionic transportation increase [18][19][20].…”