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In this work, we have analysed the effects of adding CaTiO3 (CTO) and changing the temperature on the dielectric and electric properties of ceramic matrix BiVO4 (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. [ABSTRACT FROM AUTHOR]

In this work, the dielectric and electric properties of the ceramic matrix BiVO4 (BVO) and the effects of the addition of TiO2 were analysed by impedance spectroscopy (IS). The BVO phase was calcined at 773 K and used to prepare the composite ceramic which the titanium oxide was added (15, 30 and 60 wt% TiO2), molded in pellet shape and sintered at 1073 K. These samples were characterized by X-ray diffraction (XRD). The thermo-activated charge transfer process for the ceramics BVO with the respective additions was observed and the electric results were compared with the electric response of equivalent circuit composed of three associations in parallel with R-CPE and represented by the Nyquist diagram. At room temperature and in the frequency range of 1 Hz, the samples presented high relative permittivity, εr = 26k to approximately 35k, and a dielectric loss at the order of 10−2 at 1 MHz. The composites presented negative and positive values of the temperature coefficient of capacitance (TCC) along TiO2 composition. Through IS coupled with temperature variation, the activation energies were measured; the values showed decrease with increasing withTiO2 concentration. [ABSTRACT FROM AUTHOR]