Ferroelectric, piezoelectric and electrostrictive properties of Sn4+-modified Ba0.7Ca0.3TiO3 lead-free electroceramics

Lead-free Ba0.7Ca0.3Ti1-xSnxO3 (x=0.00, 0.025, 0.050, 0.075, and 0.1, abbreviated as BCST) electroceramic system was prepared by the solid-state reaction method and its ferroelectric, piezoelectric, and electrostrictive properties were investigated. X-ray diffraction shows that the compositions with x <= 0.05 exhibit a tetragonal crystal structure having P4mm symmetry; while the compositions x=0.075 and 0.1 exhibit a mixed P4mm+Amm2 phase coexistence of tetragonal and orthorhombic and P4mm+Pm (3) over barm pseudo-cubic lattice symmetries, respectively, at room temperature. The dense microstructure having relative density similar to 90%-92% and average grain size in the range similar to 2.36 mu m to 8.56 mu m was observed for BCST ceramics. Temperature-dependent dielectric measurements support the presence of phase coexistence and show the decrease in Curie temperature (T-C) with Sn4+ substitution. The dielectric loss (tan delta) values in the temperature range (-100 degrees C to 150 degrees C) was observed to be <4%, for all BCST ceramics. The BCST compositions exhibit typical polarization-electric field (P-E) hysteresis and electric field induced strain (S-E) butterfly loop, which confirms the ferroelectric and piezoelectric character. The compositions x=0.025, 0.05 and 0.075 show the peaking behavior of displacement current density (<(J)over right arrow>) to an applied electric field ((E) over right arrow) (J-E) which implies the saturation state of polarization. The maximum electrostrictive coefficient (Q(33)) value of 0.0667 m(4)/C-2 was observed for x=0.075 and it is higher than some of the significant lead-based electrostrictive materials. The compositions x=0.05 and 0.075 exhibit the notable electrostrictive properties that may be useful for piezoelectric Ac device applications. The observed results are discussed and correlated with the structure-property-composition.