Correlation of phonon characteristics and crystal structures of Ba[Zn1/3(Nb1−xTax)2/3]O3 solid solutions

Abstract

The Ba[Zn1/3(Nb1−xTax)2/3]O3 (BZNT, x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions were synthesized by conventional solid-state sintering technique. Vibration spectra (Raman spectroscopy) and x-ray diffraction (XRD) were employed to evaluate the correlation between crystal structures and vibration modes of these solid solutions as a function of Nb5+ ions replaced by Ta5+ ions. Spectroscopic and structural data show sensitivity to sample structural evolution with Ta5+ concentration. It is verified that these ceramics present a phase transition with increasing Ta5+ content, from cubic (x = 0 and x = 0.2) to hexagonal (x = 0.8 and x = 1). Raman results show that the samples of x = 0.4 and 0.6, which have a pseudocubic structure, are of the transition phases, and the 1:2 ordering degree increases and the BZNT ceramics decrease in the crystal symmetry with Ta5+ concentration. Tilting of oxygen octahedra is the main reason for phase transition. The phonon modes of the vibration spectra were assigned, the position and width were determined, and the correlation of phonon vibrations with the crystal structures for the different atoms substituted in B″-site was found.