Grain refinement and non-ohmic properties in (Co, Ta)-doped SnO2 ceramics by Cr2O3 additions and the in situ formation of CoCr2O4

In this investigation, the microstructure and current–voltage properties of (Co, Ta)-doped SnO 2 ceramics were found to depend on Cr 2 O 3 additions. SnO 2 –Co 3 O 4 –Ta 2 O 5 ceramics with additions of 0, 0.05, 0.1, 1 and 2 mol% Cr 2 O 3 were sintered at 1350 °C under an oxidizing atmosphere and characterized microstructurally and electrically. Characterization by XRD and SEM shows that for samples with 0–1.0 mol% Cr 2 O 3 , the microstructure consists of single-phase SnO 2 grains, while for the sample with the highest Cr 2 O 3 content, the CoCr 2 O 4 spinel phase is present in SnO 2 microstructure. Moreover, reduced grain size distribution breadth and average grain size are observed in the SnO 2 microstructure with 2 mol% Cr 2 O 3 . Results suggest that nonlinearity coefficient ( α ) is not as sensitive as electric field at fixed current density ( E B ) to Cr 2 O 3 concentration changes.