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 (T-C) from 114 degrees C to 72 degrees C and an increase in the orthorhombic-tetragonal (T-OT) phase transition temperature from 9 degrees C to 27 degrees 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 (epsilon(r)) similar to 4380 at 1.5 kHz frequency, piezoelectric coefficient (d(33)) similar to 431 pC/N, electrostrain (S) similar to 0.142%, and converse piezoelectric coefficient (d(33)*) similar to 403 pm/V.