Electron paramagnetic resonance investigation of acceptor centers in Pb(Zr,Ti)O-3 ceramics

The nature of extrinsic point defects in lead zirconate titanate (PZT) ceramics of various compositions prepared by solution chemistry has been explored. Using electron paramagnetic resonance (EPR), several impurity sites have been identified in the as-received materials, which include FE(3+)-oxygen vacancy (V-O(..)) complier and isolated Cu2+ ions; both of these ions are incorporated into the lattice by replacing the Ti (Zr) ion. A Fe3+-V-O(..) complex serves as a sensitive probe of the local crystalline field environment of the ceramic; the symmetry of this defect is roughly correlated with its phase diagram as the composition is varied from PbTiO3 to PbZrO3. The Fe3+-V-O(..) complex experiences tetragonal, rhombic, or orthorhombic symmetry as the composition is varied from PbTiO, to PbZrO3. As the composition of the Cu2+ ion is varied, it appears as though the addition of Zr, and nor necessarily a change in phase, is largely responsible in determining the local environment of this acceptor impurity. Also, the Cu2+ resonance parameters weakly reflect the relative Ti-O (Zr-O) bond covalency in the perovskite lattice.