Piezoelectric performance of 0.5BaZr0.2Ti0.8O3-0.5Ba1-xCaxTiO3 at triple phase point

0.5BaZr0.2Ti0.8O3-0.5Ba1-xCaxTiO3 ceramic samples with x = 15–35% have been fabricated to investigate the composition-driven phase evolution, ferroelectric, and piezoelectric properties. X-ray diffraction and temperature-dependent permittivity studies reveal the structural phase transition from the rhombohedral (R) to R + orthorhombic (O) and then O + tetragonal (T) having a tricritical triple phase points consisting of the R + O + T at x = 29.6%. The average grain size tends to increase with x but there is an exception of reducing grain size for x = 29.6%. The triple phase point displays the outstanding properties, such as minimum relaxation time (τ = 6.4 ms), large piezoelectric response (d33 = 543 pC/N), high saturation polarization (PS = 16.5 μC/cm2), small coercive field (Ec = 0.6 kV/cm), and high dielectric permittivity, over 8700 peaking at 21,765. These parameters reduce drastically at the O/R and O/T phase boundaries. Our studies indicate the important role of multiphase coexistence for enhancing the piezoelectric properties.