Defect dipole-induced high piezoelectric response and low activation energy of amphoteric Yb3+ and Dy3+ co-doped 0.5BaTi0.8Zr0.2O3-0.5Ba0.7Ca0.3TiO3 lead-free ceramics

Abstract Co-doping of piezoelectric ceramics by amphoteric rare earth ions has resulted in synergistic improvement of their electrical properties. In this study, Yb3+ and Dy3+ co-doped lead-free 0.5BaTi0.8Zr0.2O3-0.5Ba0.7Ca0.3TiO3 nanoparticles and ceramics were prepared. The synthetic process of the nanoparticles by a modified Pechini polymeric precursor method was studied by FT-IR, TG-DSC, HRTEM, XRD, and Raman spectroscopy. The densified (>96%) ceramics were obtained by sintering the as-synthesised nanoparticles at 1220 °C, and the influence of Yb content (x) on the phase structure, permittivity, ferroelectricity, piezoelectricity, and thermophysical performances was studied. Initially, for low x, Yb3+ occupied A sites in the perovskite structure as donor dopants, resulting in improved ferroelectric and piezoelectric properties and decreased domain switching activation energy with few oxygen vacancies; while the electrical properties deteriorated as x increased further. The relationships of the defect dipole-induced electrical properties or/and activation energy with internal stress, structure distortions, and impurity phase were deduced. The optimum piezoelectric coefficient (d33* = 683 p.m./V) with the lowest domain switching activation energy (Ea = 0.233 eV) was determined at x = 0.60 mol%, indicating that the ceramics were suitable for practical applications.