Abstract
Intrinsic double ionized lead vacancies and oxygen vacancies simultaneously exist within PZT compositions and create a defect dipole. Acceptor dopants with a valence of +3 induce extrinsic single ionized oxygen vacancies whereas donor dopants with a valence of +5 induce extrinsic single ionized lead vacancies. An electron exchange can exist between single and double ionized vacancies that it was facilitated in the case of single ionized lead vacancies. As a consequence, such a transfer occurred mainly for soft PZT and almost never for hard PZT. Based on this transfer, this paper explains the softening effect and the squeeze ignition mechanism.