Phonon characteristics, crystal structures and intrinsic properties of non-stoichiometric Ba_1+xWO₄ ceramics

Scheelite-type non-stoichiometric Ba 1+ x WO 4 (0 ≤ x ≤ 0.04) ceramics were synthesized by a conventional solid-state reaction method. X-ray diffraction patterns showed that the main phase is a tetragonal scheelite structure with space group I4 1 /a. The vibrational modes were obtained from Raman spectra, which were assigned and illustrated. The intrinsic properties were obtained by Clausius-Mosotti equation (C–M) and the damping equation, and there is a positive relationship between the FWHM values of the B g (Ba) modes and the dielectric losses (calculated by the damping equation), as well as a negative correlation between the Raman shifts of the E g (near 355 cm −1 ) and the dielectric constants (deduced by C–M equation). The far-infrared reflectivity spectra were analyzed by the four-parameter semi-quantum (FPSQ) model to calculate the intrinsic properties of the samples, which agreed well with those values obtained by the measured data.