Site occupancy of Li ions in Li-doped K(Ta1- x Nb x )O3 single crystals: reanalysis of inelastic light scattering data and first-principles calculations

Abstract

The Li-doping effects of KTa1- x Nb x O3 (KTN) crystals on the site occupancy were investigated by reanalysis of Raman scattering results in the literature and density functional theory (DFT) based first-principles calculations. Above the Curie temperature (T C), the transformation of the local A 1(z) mode of polar nanoregions (PNRs) of non-doped KTN into the E(x,y) mode of PNRs was reported in 5%Li-doped KTN. The site occupancy for 5%Li-doped-KTN was estimated using DFT results, and it shows that 4.2%Li ions occupy at A-site, while the 0.8%Li ions occupy at B-site. In 5%Li-doped KTN crystals, the hetero-valence random occupation of 0.8%Li ions at B-site can be the microscopic origin of the change of the local mode of PNRs.