Influence of co-dopants average valence on microstructural and electromechanical properties of lead titanate ceramics

Effects of Ni, Nb and Mn co-doping on microstructural, dielectric and electromechanical properties of lead titanate (PT) dense ceramics, obtained as a result of decreasing lattice anisotropy with increasing amount of co-dopants, were investigated.Different values of the average valence (AV) of Ni–Nb co-dopants were obtained by mutual valence compensation between these acceptor–donor ions of various relative concentrations.Significantly higher amounts of Mn2+ (resulted by reduction of Mn4+ in presence of donor co-dopants) were found in materials with Ni–Nb AV > 4+. These materials show higher coupling factors, correlated with higher mechanical quality factors, compared to the rest of materials. Hard-like piezoelectric behavior was manifested in materials with Ni–Nb AV < 4+, whereas ceramics with Ni–Nb AV > 4+, and without manganese, turned out to have a soft-like behavior.Electromechanical properties of PT ceramics are discussed in terms of average valence of Ni–Nb co-dopants and multivalence state of manganese.