Lead-free piezoelectric compositions based on (Ba,Ca)(Zr,Ti)O 3 have been reported to exhibit many piezoelectric properties similar to the conventionally used Pb(Zr,Ti)O 3 materials, and have thus been attracting much attention as potential replacements for lead-based piezoceramics. However, there appears quite a wide variation in the reported piezoelectric properties of the BCZT ceramics, indicating that such properties may be sensitive to fabrication and processing methods. This paper reports an investigation of a wide range of processing factors, including composition (e.g. ratio of Ba(Zr,Ti)O 3 to (Ba,Ca)TiO 3 ), sintering conditions (temperature and cooling rate), particle size of the calcined ceramic powder, structure and microstructure (e.g. phase, lattice parameters, density and grain size), and their effect on the piezoelectric properties. For individual compositions, lattice constants and grain size, which are themselves dependent on the ceramic powder particle size and sintering conditions, have been shown to be very important in terms of optimising piezoelectric properties in these materials.

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The preparation of Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT) powders by wet chemical methods has been investigated, and the powders used to explore relationships between the microstructure and piezoelectric properties (d 33 coefficient) of sintered BCZT ceramics. Sol-gel synthesis has been shown to be a successful method for the preparation of BCZT nanopowders with a pure tetragonal perovskite phase structure, specific surface area up to 21.8 m 2 /g and a mean particle size of 48 nm. These powders were suitable for the fabrication of dense BCZT ceramics with fine-grain microstructures. The ceramics with the highest density of 95% theoretical density (TD) and grain size of 1.3 lm were prepared by uniaxial pressing followed by a two-step sintering approach which contributed to the refinement of the BCTZ microstructure. A decrease in the grain size to 0.8-0.9 lm was achieved when samples were prepared using cold isostatic pressing. Using various sintering schedules, BCZT ceramics with broad range of grain sizes (0.8-60.5 lm) were prepared. The highest d 33 = 410.8 AE 13.2 pC/N was exhibited by ceramics prepared from sol-gel powder sintered at 1425°C, with the relative density of 89.6%TD and grain size of 36 lm.