Title: High Thermal Stability of the RF dielectric properties of the BiVO4 matrix added with ZnO

Abstract

In this work, the complex impedance spectroscopy study of bismuth vanadate ceramics (BiVO4) ceramics with different additions of ZnO (25, 50 and 75 wt%) it is performed. The BiVO4 (BVO) was synthesized by the reaction method in solid state and calcined at 500 ºC and the BVO-ZnO composites were molded in sintered ceramic pellets at 700 ºC. The X-Ray Diffraction (XRD) was used to analyze he crystal structure of BVO and composites BVO-ZnO, none being observed synthesis spurious phase. Analysis by Complex Impedance Spectroscopic (CIS) showed that increasing the concentration of ZnO, reveals the presence of a thermo-activated charge transfer process with activation energy increasing for the sample with 25 wt% ZnO. At room temperature, the increase in the ZnO concentration in the BVO matrix maintained the high value of the dielectric constant (ε), in the order of 104 at the frequency of 1 Hz. The temperature coefficient of capacitance (TCC) displayed positive in the BVO and negative for composites. The adjustment through the equivalent circuit, presented excellent electrical response for the composites, being identified an association with three Resistors (R), each in parallel a Constant Phase Element (CPE), showing the influence of grain and grain boundary in the process of thermoactive conduction.