From structure to conduction mechanism: investigating the effect of sintering atmosphere and the role of Mn in Ca0.6Sr0.4TiO3 ceramics

Abstract

The effects of sintering atmospheres (air, O2, and N2) and defect chemistry role of Mn in the structure, electrical properties, and conduction mechanism of Ca0.6Sr0.4TiO3 (CST) ceramics were extensively investigated in this study. O2 atmosphere sintering resulted in a decrease in the concentration of oxygen vacancies, as revealed by the expanded unit cell and increased Ti ions' valence state. The reverse was the case for samples sintered in N2. Interestingly, sintering in both of O2 and N2 resulted in deteriorated bulk resistivity, due to the transition of the conduction mechanism (n-type electronic→ionic→p-type electronic conduction) with increasing oxygen partial pressure (PO2). This was verified by subjecting the samples to annealing treatment in different atmospheres and measuring their high-temperature equilibrium conductivities. Additionally, Mn-doped CST ceramics demonstrated higher resistivity than that of the pure CST ceramics, regardless of the sintering atmospheres, which could be attributed to the self-changing of Mn ions’ valence state in different PO2.