From tin oxalate to (Fe, Co, Nb)-doped SnO2: Sintering behavior, microstructural and electrical features

Highly reactive SnO2-doped nanocrystalline powders with average particle size of 20 nm and specific surface areas above 30 m2/g were obtained through the polymeric precursor method with tin oxalate (SnC2O4) as a chloride-free precursor for SnO2. Powders and sintered discs were characterized by means of X-ray powder diffraction (XRD), SEM and TEM. The influence of Co and Fe on the microstructure development and on the electrical properties of dense SnO2-based ceramics was studied. Co and Fe species were found to decrease in more than 70 °C the sintering temperature of SnO2 with respect to mixed oxide procedures. Secondary phases enriched in Co and Fe were detected and identified in sintered samples with XRD. Current–voltage curves were registered for electrical characterization. Doping with iron increased the electrical breakdown field and a nonlinearity coefficient of 20 was achieved.