Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ferroelectric ceramics with refined microstructure and high strain under electric field by mechanosynthesis

Abstract

Lead-free ferroelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 stands out among environmentally friendly alternatives to commercial Pb(Zr,Ti)O3 piezoceramics for its large piezoelectric coefficients, and it is especially suitable for applications in which thermal depoling is not an issue like bio-implanted devices. However, ceramic processing by conventional means consistently results in exaggerated grain growth, which compromises reliability and has prevented its transfer to industry. We report here the application of high-energy milling for the mechanosynthesis of nanocrystalline Ba0.85Ca0.15Zr0.1Ti0.9O3 powders with enhanced reactivity, and to the control of grain growth during ceramic processing to obtain materials with tailored microstructures and decreasing grain sizes down to the sub-10 µm range. Characterization of the electrical and electromechanical properties was accomplished and uncovered triggering of a new mechanism for very large strain under electric field in fine-grained ceramics. Process optimization by precursor selection and preliminary up-scaling studies are also presented.