EFFECT OF COMPOSITION AND TEMPERATURE ON ELECTRIC FATIGUE OF LA-DOPEDLEAD-ZIRCONATE-TITANATE CERAMICS

Composition and temperature of ferroelectric La-doped lead zirconate t itanate ceramics influence its electric fatigue behavior, defined as t he degradation of the electrical properties under the action of an ac field applied for a long time. Compositions of rhombohedral symmetry e xhibit little or no fatigue compared with those of tetragonal and orth orhombic symmetry. At temperatures higher than the dielectric maximum, no fatigue effect was detected. Compositions close to phase boundarie s (FE-AFE, FE-FE, or FE-PE) display significant fatigue behavior. Elec tric fatigue arises from the pinning of domains by space charges or in jected carriers or from microcracking. The former (which are charge re lated) is accompanied by smaller strains and is recoverable by thermal and electrical treatment, while the latter (arising from microcrackin g) arises from large incompatible stresses between grains and is a per manent damage. The understanding of the mechanism of electric fatigue gained in the present study provides guidelines for enhancing the long -term reliability of devices based on ferroic materials.