Abstract
The shift of the morphotropic phase boundary (MPB) in the PZT system under the influence of electric fields and uniaxial stresses parallel to the z-axis is calculated according to the phenomenological theory of Devonshire. Two sets of coefficients were used to describe the Gibbs free energy. The first one has been fitted to a modified PZT ceramic; the second one has been published by Amin et al. for pure PZT ceramics. If electric fields are applied the MPB is shifted towards higher zirconium concentration by about 0.10 to 0.15 mole% Zr per kV/cm. This shift is reversed by compressive stresses, whereas tensile stresses have the same effect as electric fields.