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

摘要

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 Fe~(3+)-oxygen vacancy (V_O) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe~(3+)-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 PbTiO_3 to PbZrO_3. NMR spectra ~(207)Pb in PbTiO_3, PbZrO_3 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.