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 b een explored. Using electron paramagnetic resonance (EPR), several imp urity sites have been identified in the as-received materials, which i nclude FE(3+)-oxygen vacancy (V-O(..)) complier and isolated Cu2+ ions ; both of these ions are incorporated into the lattice by replacing th e Ti (Zr) ion. A Fe3+-V-O(..) complex serves as a sensitive probe of t he local crystalline field environment of the ceramic; the symmetry of this defect is roughly correlated with its phase diagram as the compo sition is varied from PbTiO3 to PbZrO3. The Fe3+-V-O(..) complex exper iences tetragonal, rhombic, or orthorhombic symmetry as the compositio n 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 necessaril y a change in phase, is largely responsible in determining the local e nvironment of this acceptor impurity. Also, the Cu2+ resonance paramet ers weakly reflect the relative Ti-O (Zr-O) bond covalency in the pero vskite lattice.