Dielectrical and structural studies of composite matrix BiVO 4 –CaTiO 3 and temperature effects by impedance spectroscopy

In this work, we have analysed the effects of adding CaTiO 3 (CTO) and changing the temperature on the dielectric and electric properties of ceramic matrix BiVO 4 (BVO) in the radiofrequency range. BVO was synthesized by a calcination process at 500 °C and ceramic composites were prepared by the addition of CTO (8, 16, 24, 28 and 32 wt%). These composites were moulded in ceramic pellets and sintered at 800 °C. The crystal structures of BVO and composites were analysed by X-ray diffraction and no spurious phase was detected in the synthesized BVO. Complex impedance spectroscopy observed the presence of a thermo-activated charge transfer process with activation energy increasing with CTO concentration in the samples. The dielectric constant ( ε ) measured in radio frequency for ceramic composites presented high values that ranged from 26 to 9 k for BVO to BV32, respectively, at room temperature and a frequency of 1 Hz. The electrical response obtained by composites were fitted through an equivalent circuit composed of three associations in parallel with the resistance of a constant phase element, which showed minor deviations between the fitted and experimental data. The temperature coefficient of capacitance displayed negative and positive values in CTO-based composites and pure BVO, respectively; these characteristics are favourable for the application of composites in the radio frequency band.