Ferroelectric properties and fatiguing effects of modified PbTiO3 ceramics

Abstract

The ferroelectric properties of fine-grained PbTiO3 ceramics modified by small amounts of La and Mn have been investigated using both quasi-static (∼ 0.05 Hz) and more dynamic (0.5-50 Hz) electric driving fields.Information about the domain reorientation processes were obtained from lateral switching strain and hysteresis loop measurements with low-frequency fields. The lateral remanent switching strain is ∼70.10-5, the remanent polarization ≲ 30 μC/cm2, and the coercive field strength ≳ 40 kV/cm. The number of domains switched by 90° is small (≲10%) but 180° domain alignment is virtually perfect. The spontaneous polarization of PbTiO3 single crystals is estimated to be ∼75 μC/cm2. Polarization reversals under more dynamic conditions (10-50 Hz sine wave excitation) result in the occurrence of fatiguing effects. SEM techniques revealed microcracking as the cause of this degradation behaviour. The cracks run along grain boundaries and they are confined to a surface layer of ≲ 15 grain diameters.