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.

Lead zirconate titanate (PZT) is the excessively used material for electromechanical device applications for decades. However, the toxic effects of absorption of metallic lead by the human body can cause lethal poisoning. 1 Consequently, European Union adopted various regulations. 2,3 As a response, in 2004 Saito et al 4 reported (K,Na)NbO 3 (KNN)-based lead-free piezoceramics with properties comparable to those found in PZT. Functional properties of BaTiO 3 (BT)-based ceramics were insufficient compared to PZT-based materials together with low

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We report a large piezoelectric constant (d33), 720 pC/N and converse piezoelectric constant (d33*), 2215 pm/V for 0.55(Ba0.9Ca0.1)TiO3‐0.45Ba(Sn0.2Ti0.8)O3 ceramics; the biggest value achieved for lead‐free piezoceramics so far. The ceramic powders were calcined between 1050°C‐1350°C and sintered at 1480°C. The best properties were obtained at a calcination temperature (CT) of 1350°C. The fitting combination of processing and microstructural parameters for example, initial powder particle size >2 µm, ceramics density ~95%, and grain size ~40 µm led to a formation of orthorhombic‐tetragonal‐pseudo‐cubic (O‐T‐PC) mixed phase boundary near room temperature, supported by Raman spectra, pointed to the extremely high piezoelectric activity. These conditions significantly increase piezoelectric constants, together with high relative permittivity (εr) >5000 and a low loss tangent (tan δ) of 0.029. In addition, the d33 value stabilizes in the range of 400‐500 pC/N for all samples calcined between 1050°C and 1250°C. The results entail that the (Ba,Ca)(Sn,Ti)O3 ceramics are strong contenders to be a substitute for lead‐based materials for room temperature applications.