Effect of excess PbO on phase formation and properties of (Pb0.90Ba0.10)ZrO3 ceramics

Polycrystalline samples of (Pb0.90Ba0.10)ZrO3 (PBZ) were prepared by a mixed oxide, solid-state reaction method. Excess PbO (3, 5 or 10 wt.%) was introduced prior to powder calcination to compensate for any PbO that may have been lost from the samples due to volatilisation during heat treatments. X-ray diffraction revealed that, compared to samples made from stoichiometric starting mixtures, a starting excess of PbO of : >= 3 wt.% increased the proportion of the rhombohedral PBZ phase which coexisted with the antiferroelectric orthorhombic phase. Microstructurally, excess PbO produced an increase in average grain size, from similar to 1 mu m for no excess to similar to 1.5 mu m for >= 3 wt.% excess PbO. The fractured surfaces indicated predominantly intra-granular fracture in samples with no added PbO, or 3 wt.% excess PbO, whereas the 5 and 10 wt.% excess PbO samples displayed mainly inter-granular fracture. Dielectric constant-temperature plots showed a maximum peak value of 12,700 for the 3 wt.% sample which was also the most dense sample. (C) 2005 Elsevier B.V All rights reserved.