Orthorhombic-tetragonal phase coexistence and enhanced piezoelectric properties at room temperature in Zn and Ta modified (BaCa)(ZrTi)O ceramics through the synergistic effect of lattice distortion.

This study provides a fundamental understanding of the enhanced piezoelectric properties in ABO perovskite based lead-free piezoelectric materials. For this we synthesized (BaCa)(ZrTi (ZnTa) )O((1 - )BCZT-()ZT) ( = 0.00, 0.005, 0.01, and 0.02) solid solutions exhibiting high piezoelectric response. The (1 - )BCZT-ZT materials are synthesized by a high-temperature solid-state ceramic reaction method by varying in the full range ( = 0.00-0.02). In-depth exploratory research is performed on the structural, dielectric, ferroelectric, and piezoelectric properties of (1 - )BCZT-()ZT ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X-ray diffraction (XRD) analyses, which also reveals that the Ca, Zr, Zr and Ta are well dispersed within the BaTiO lattice. For all (1 - )BCZT-()ZT ceramics, thorough investigation of phase formation and phase-stability using XRD, Rietveld refinement, Raman spectroscopy, and temperature-dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (2 + 4) phases at room temperature. The steady transition of 2 crystal symmetry to 4 crystal symmetry with increasing content is also demonstrated by Rietveld refinement data and related analyses. The / ratio of the tetragonal phase greatly influenced the electric properties of the ceramics. The / ratio of the tetragonal phase increases from 1.0112 for = 0 to 1.0157 for = 0.005 and subsequently decreases to 1.0038 for = 0.02. When the / of the tetragonal phase reaches its maximum value, the ceramic with = 0.005 has the best piezoelectricity ( ∼ 297 pC N). The calculated degree of relaxation () increases with the increase in BZT content, indicating that the BCZT-BZT ceramics are ferroelectric materials with diffuse phase transition. Main dielectric, piezoelectric and ferroelectric parameters of (1-)BCZT-ZT ceramics were optimized around = 0.005 with a high piezoelectric coefficient ( = 297 pC N), a remnant polarization ( = 7.58 μC cm), spontaneous polarization ( = 10.25 μC cm) and a high dielectric constant ( = 4449 at and 2330 near RT) at 1 kHz, indicating promising applications for lead-free piezoelectric ceramics.