The nature of the defect structure of solid solutions based on lead zirconate titanate (PZT): Evidence from EPR and NMR

The nature of intrinsic and impurity point defects in lead zirconate titanate (PZT) ceramics has been explored. Using electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) methods several impurity sites have been identified in the materials, including Fe³⁺-oxygen vacancy (V_O) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe³⁺-V_O paramagnetic complex serves as a sensitive probe of the local crystalline field in the ceramic; the symmetry of this defect is roughly correlated with PZT phase diagram as composition is varied from PbTiO₃ to PbZrO₃. NMR spectra ²⁰⁷Pb in PbTiO₃, PbZrO₃ and PZT with iron content from 0 to 0.4 mol % showed that increasing the iron concentration leads to a distortion of the crystal structure and improve the electrophysical parameters of the piezoceramics. This is due to the formation of the phase, which has a higher symmetry, but at high concentrations of iron (> 0.4 mol. %) leads to sharp degradation of electrophysical parameters.