The effect of A site non-stoichiometry on 0.94(NayBix)TiO3-0.06BaTiO3

A good knowledge of the defect chemistry of a lead free piezoelectric ceramic enables the control of electromechanical properties and microstructure. Especially for (NayBix)TiO3, it was already shown that certain acceptor doping and Bi deficiency lead to vastly increased oxygen ionic conductivity rendering it unsuitable for piezoelectric applications. In this work, the focus is on the more relevant 0.94(NayBix)TiO3-0.06BaTiO3 (NyBxT-BT) solid solution. There is an increase in conductivity due to Bi deficiency but it is by far not as extensive as for pure NBT. While Bi deficiency leads to a dominating ionic contribution for NBT material, electronic conductivity can still be dominant for NBT-BT. However, not only the conductivity or dielectric loss is influenced by the presence of defects, but also the grain growth and piezoelectric constants. Hence, the control of the stoichiometry is very important and offers a new way to modify the piezoelectric response.