Evolution of microstructure and impedance upon the sintering of a Bi–Pr–V-based fluorite-type oxide conductor

Samples of Bi0.85Pr0.105V0.045O1.545, a fluorite-type oxide conductor, with varying porosities and different average grain sizes determined by the sintering temperature (500–900 °C), were investigated using scanning electron microscopy (SEM) and impedance spectroscopy. Sintering treatment leads to increased density of ceramic materials between 500 and 800 °C and predominantly to grain growth at higher temperatures, in dense samples (porosity <4%). pedance diagram for these materials is composed of a high-frequency domain characteristic of the electrical properties of the ceramic itself and a low-frequency domain attributed strictly to electrode response. The impedance diagram of the ceramic is a single semicircle. Grain boundaries and porosity do not lead to the appearance of a separate semicircle. The influence of sintering temperature on electrical properties may be parameterized by total electrical resistance, depression angle and relaxation frequency as seen by curve fitting of the impedance diagram. The variation of electrical conductivity and dielectric constant as a function of sample porosity are reported and discussed.