Synthesis and electrical properties of Bi2V1 − x Ge x O5 + y solid solutions

Abstract

A continuous series of Bi2V1 − x Ge x O5 + y solid solutions has been prepared by solid-state reactions, and their polymorphism and electrical properties have been studied. The solid solutions with 0 < x ≤ 0.2 are isostructural with the monoclinic phase α-Bi2VO5.5, and those with 0.2 < x ≤ 0.3 are isostructural with the orthorhombic phase. In the range 0.6 ≤ x < 1, the solid solutions have the orthorhombic Bi2GeO5 structure. The solid solutions with 0.4 ≤ x ≤ 0.5 have a tetragonal structure. Increasing the germanium content suppresses the ferroelectric phase transition in the Bi2VO5.5-based solid solutions, without changing the transition temperature. With increasing vanadium content, the conductivity of the solid solutions gradually increases, from 3 × 10−5 (x = 1) to 3 × 10−1 S/cm (x = 0) at 550°C.