Influence of compacting pressure on the electrical properties of ZnO and ZnO:Mn ceramics

Undoped and Mn-doped ZnO ceramics were prepared from the powders compacted at different pressures and sintered in air at high temperature. Their structural, optical, light emitting and electrical characteristics as well as the distribution of chemical elements were studied. It was found that an increase in compacting pressure stimulates an increase in direct current conductivity in both undoped and doped samples. In the case of doped samples, this effect was accompanied by a decrease in the height of potential barriers at the grain boundaries. It is found that electron concentration in ceramic grains, estimated from the modelling of infrared reflection spectra, remained relatively constant. The analysis of luminescence spectra and spatial zinc distribution revealed that the increase in compacting pressure results in the accumulation of interstitial zinc at the grain boundaries forming channels with enhanced conductivity. These findings provide an explanation for the evolution of electrical properties of ceramic samples with compacting pressure. Article Highlights ZnO and ZnO:Mn powders compacted with different pressure were sintered in air. The rise of compacting pressure enhances electrical conductivity of the ceramics. Compacting pressure decreases the superlinearity of I-V curves in ZnO:Mn. The formation of conductive channels was observed in both ZnO and ZnO:Mn. Zinc accumulation at grain boundaries favours conductive channels formation.