Development of mixed phase with improved dielectric and piezoelectric properties in Ca and Sn modified BaTiO3 ceramics

In the present study, we investigated the structural, dielectric and piezoelectric properties of lead-free polycrystalline BaTiO3 (BT) and Ba0.95Ca0.05Ti0.95Sn0.05O3 (BTCS) ceramics. The ceramics were synthesized using the conventional solid-state reaction route. Rietveld analysis confirmed a tetragonal symmetry (space group P4mm) in BT ceramic, and a double-phase coexistence of tetragonal and orthorhombic (space group Amm2) symmetry in BTCS ceramic at room temperature. The dielectric study revealed a decrease in the Curie temperature (TC) from 114 °C to 72 °C and an increase in the orthorhombic-tetragonal (TOT) phase transition temperature from 9 °C to 27 °C in comparison to the same structural transitions of BT system. Further, the BTCS ceramic exhibited a relaxor ferroelectric behavior with frequency dispersion and diffused phase transitions. Due to the T-O phase coexistence, significant enhancements in the dielectric and piezoelectric properties were observed in the BTCS ceramic at room temperature, with a giant RT dielectric constant (Ɛr) ~ 4380 at 1.5 kHz frequency, piezoelectric coefficient (d33) ~ 431 pC/N, electrostrain (S) ~ 0.142%, and converse piezoelectric coefficient (d33⁎) ~ 403 pm/V.