Study of the Valence State of the Manganese Ions in PbTiO3 Ceramics by Means of ESR

ESR measurements have been carried out on Mn ions in PbTiO3 ceramics. Mn ions in the PbTiO3 ceramics are incorporated at Ti4+ sites with mixed valence states of Mn2+ and Mn4+. The proportion of Mn2+ ions is the highest for the calcined powder and changes during the firing process. After the firing it decreases with increasing the firing temperature in the range from 800°C and 1100°C, and increases at temperatures above 1150°C. Additionally, the proportion changes with the amount of Mn ions. The proportion of Mn2+ decreases with increasing Mn dopants up to 0.20 wt%. In the range from 0.20 wt% and 0.25 wt% of MnO2 it increases steeply, and the Mn2+ and Mn4+ ratio is not varied when more than 0.25 wt% MnO2 is doped. Piezoelectric properties of Mn doped PbTiO3 can be explained by the changes of the valence states of Mn ions.