The effect of grain size on the high field dielectric properties of hard PZT ceramics

Hard (Mn-doped) PZT ceramics having grain sizes in the range 4 to 9 μm were subjected to an AC electric field with an amplitude E0 of 0.1 to 3.5 kV mm-1. The dielectric characteristics were determined by analysis of the measured P-E (polarisation-electric field) hysteresis data. It was found that the saturation polarisation Ps, measured at a field amplitude of 3.5 kV mm-1, reduced from 29 to 21 μC cm-2 as the grain size reduced from 7.1 to 4.1 μm, indicating an increased resistance to ferroelectric domain switching in the fine-grained material. In contrast, the dielectric permittivity and loss (εr′, εr″), measured in the field range below the coercive field Ec, both increased with a reduction in grain size; this was attributed to an increase in the domain wall density in fine-grained ceramics. Near-linear εr′-E0 Plots were obtained for 0.3 kV mm-1