Structure, dielectric and piezoelectric properties of Ba0.90Ca0.10Ti1−xSnxO3 lead-free ceramics

Lead-free piezoelectric ceramics Ba0.90Ca0.10Ti1−xSnxO3 have been prepared by a conventional ceramic fabrication technique and the effects of Sn4+ on the structure, dielectric and piezoelectric properties of the ceramics have been investigated. All the ceramics exhibit a pure perovskite structure. After the substitution of Sn4+, the crystal structure of ceramics is transformed gradually from a tetragonal to an orthorhombic phase, and becomes a pseudo-cubic phase at x≥0.14. The substitution also decreases the Curie temperature greatly from 138 °C at x=0 to 33 °C at x=0.12, and shifts the orthorhombic–tetragonal phase transition to higher temperatures. Coexistence of the orthorhombic and tetragonal phases is formed in the ceramic at x=0.10, leading to significant improvements in the piezoelectric properties: d33=521 pC/N and kp=45.5%. Our results also reveal that the ceramics sintered at higher temperatures contain larger grains, and thus exhibit more noticeable tetragonal–orthorhombic phase transition and enhanced ferroelectric and piezoelectric properties.