Coexistence of 1 : 2 and 1 : 1 long-range ordering types in La-modified Ba(Mg0.33Ta0.67)O3 ceramics

Abstract

The ordering structure of lanthanum-substituted Ba(Mg_0.33Ta_0.67)O₃ was investigated using x-ray diffraction. It was observed that the ordering type of this solid solution transformed from 1: 2 to 1: 1 with 10 mol% substitution of La(Mg_0.67Ta_0.33)O₃. These two types of ordering coexist over a wide range of composition. This coexistence of ordering types was considered as phase coexistence and its physical origin was investigated using microwave measurements. Based on the intensity of superlattice reflections and the discontinuity in dielectric properties, it was suggested that the coexistence of two ordering types originates from the overlap of the two stability regions.