BaZrO3-BaTiO3-CaTiO3 piezoceramics by a water-based mixed-oxide route: Synergetic action of attrition milling and lyophilization

This manuscript shows an innovative water-based processing route to fabricate lead-free piezoceramics. It faces the challenge of substituting conventionally used organic solvents by innocuous water. The procedure involves two methods of widespread use in industry: attrition ball-milling and freezing-lyophilization. Powders with nominal composition (Ba0.92Ca0.08)(Ti0.95Zr0.05)O3 were effectively obtained. A narrow monomodal size distribution (600 nm) proved high reactivity that allowed solid-state synthesis at ultra-low temperature (700°C-2h). Optimal two-step sintering method (900°C-3h,1280°C-6h) allowed well-sintered homogeneous ceramics with pure tetragonal perovskite phase. They showed high piezo-sensitivity (d33=320 pC/N, d31=-110 pC/N, kp=31.45% and Np=2750 kHz·mm,ε′33T=3670, tanδ=0.036 at 1 kHz), comparable to that found for routes in organic media. Therefore, attrition ball milling in water and lyophilization work in synergy to successfully activate the precursors, influencing on the structural, microstructural and electrical properties of the final BCZT ceramics. This is an unprecedented development to produce piezoelectric ceramics using a sustainable, environmentally benign water-based process, with a positive impact in noteworthy industrial applications.