Dielectric and Raman scattering studies of Bi₂WO₆single crystals

Abstract

Bi2WO6 single crystals were grown by a flux method using two solvents: NaVO3–B2O3 and NaWO4. Dielectric studies were performed in the temperature range from 110 to 940 K. They showed that dielectric permittivity along the ferroelectric axis shows slight dispersion, increases with increasing temperature and reaches local maximum related to the P21 ab–B2cb phase transition at 933 K. In the direction perpendicular to the polar axis, there is no dielectric dispersion and dielectric permittivity decreases monotonically with the increase in temperature. Polarised Raman experiments were performed in the temperature range from 17 to 873 K. Based on the model of independent oscillators, frequencies and damping (full width at half maximum – FWHM) of the Raman lines were calculated. Temperature dependences of Raman line frequencies showed that modes at 57, 77, 83, 102 and 150 cm−1 exhibit soft mode behaviour.