Effects of B site ions on the relaxor to normal ferroelectric transition crossover in Ba4Sm2Zr4(NbxTa1-x)6O30 tungsten bronze ceramics

Abstract

Effects of B site ions on the relaxor to normal ferroelectric crossover in Ba4Sm2Zr4(NbxTa1-x)6O30 (x = 0, 0.3, 0.5, 0.7, 0.9, and 1) tungsten bronze ceramics were investigated. The tetragonal tungsten bronze structure in space group P4/mbm was confirmed for compositions of x = 0, 0.3, and 0.5, while space group P4bm was confirmed for compositions of x = 0.7, 0.9, and 1. With the increasing Nb content in the B site, the dielectric properties showed a crossover from the relaxor to normal ferroelectric behavior, accompanied with the disappearance of frequency dispersion, increased ferroelectric transition temperature, and larger dielectric constant value. The room temperature Raman spectra for compositions of x = 0 and x = 1 showed different vibration modes of the oxygen octahedral, and the temperature dependence of the integrated intensity of Raman bands indicated the different structural transition process. Unlike the effects of A site ions, the onset of the relaxor/normal ferroelectric behavior of Ba4Sm2Zr4(NbxTa1-x)6O30 was mainly caused by the different electron configuration of Nb and Ta.