Abnormal dielectric properties and phase transition in Bi_0.783(Mo_0.65V_0.35)O₄ scheelite-related structured ceramic

In the present work, an interesting phase transition at 150 °C in ordered scheelite structured Bi_0.783(Mo_0.65V_0.35)O₄ ceramic was observed for the first time. This phase transition was believed to be related to the ordered arrangement of A site defects (or A site cations Bi³⁺). X-ray diffraction (XRD) and Raman spectra were employed to study the structure. Thermal expansion data showed that a sudden decrease in cell volume was observed during the phase transition, which resulted in a sharp increase in dielectric permittivity and loss over a wide frequency range (100 Hz to 7.5 GHz). Far-infrared reflectivity and THz spectra were used to study the intrinsic dielectric properties. It was found that the Bi-O stretches contributed mainly to the polarization. This study extended the design of A site ordered scheelite structured materials and the knowledge of their phase transitions.