Role of lower valent substituent-oxygen vacancy complexes in polarization pinning in potassium-modified lead zirconate titanate

The dependence of polarization switching on thermal histories has been inve stigated for K1+-modified lead zirconate titanate (PZT) ceramics by Sawyer- Tower polarization methods. It was found that double-loop-like polarization characteristics in the aged condition could be reversed to normal single l oop polarization characteristics by quenching specimens from above the ferr oelectric phase transition temperature. However, the P-E curves reversed ba ck to double-loop-like characteristics after reaging specimens at elevated temperatures. Excess oxygen vacancies in La3+-modified PZT were not found t o result in double-loop-like polarization hysteresis, whereas excess oxygen vacancies in K1+-modified PZT did. These results provide evidence for role of K1+-oxygen vacancy complexes in polarization pinning. (C) 1999 American Institute of Physics. [S0003-6951(99)00929].