Correlation between structural, ferroelectric, piezoelectric and dielectric properties of Ba0.7Ca0.3TiO3-xBaTi0.8Zr0.2O3 (x = 0.45, 0.55) ceramics

Abstract

We report on the correlation between structural, ferroelectric, piezoelectric and dielectric properties of the (1-x)Ba0.7Ca0.3TiO3-xBaTi0.8Zr0.2O3 (x = 0.45, 0.55; abbreviated as 55BCT30 and 45BCT30) ceramics close to morphotropic phase boundary (MPB) region. The 55BCT30 and 45BCT30 ceramics were synthesized by the standard, high-temperature solid state ceramic method. X-ray diffraction (XRD) along with Rietveld refinement indicate that the 55BCT30 ceramics exhibit rhombohedral (R, space group R3m), orthorhombic (O, space group Amm2) and tetragonal (T, space group P4mm) phases while 45BCT30 ceramics exhibit only T and O phases. The temperature dependent Raman spectroscopy measurements confirm the structure and phase transformations observed from XRD. All the ceramics are chemically homogeneous and exhibit a dense microstructure with a grain size of 5–7 µm. The presence of polarization-electric field and strain-electric field hysteresis loops confirm the ferroelectric and piezoelectric nature of the ceramics. The polarization current density-electric field curves show the presence of two sharp peaks in opposite directions indicating the presence of two stable states with opposite polarity. Higher values of direct piezoelectric coefficient (d33 ~ 360 pC/N) were observed due to the existence of low energy barrier near MPB region and polymorphism. The 55BCT30 ceramics exhibit a higher value of electrostrictive coefficient (Q33 ~ 0.1339 m4/C2) compared to the well-known lead-based materials. The temperature dependent dielectric measurements indicate the O to T phase transition for 55BCT30 and 45BCT30. These ceramics exhibit a Curie temperature (Tc) of 380 K with a dielectric maximum of ~ 4500.