Optimization of the electrical properties on lead-free barium titanate-based piezoelectric by combining grain growth with orthorhombic-tetragonal phase boundary

Barium titanate-based lead-free piezoceramics are considered as a key material for the fabrication of dielectric capacitors due to their large relative dielectric constant (εr) and are also identified as a remarkable electrocaloric material on account of their low Curie temperature (TC) and high spontaneous polarization (Ps). At this work, to optimize the electrical performances of BaTiO3-based Pb-free piezoceramics, chemical doping was used to tailor their composition. The aim is to boost Curie temperature while sustaining decent electrical properties. Besides, to enlighten the underlying physical mechanisms, first-principles calculations based on atomic coupling, orbital hybridization as well as electron localization were carried out. The experimental results show that the dielectric, ferroelectric, and piezoelectric properties are mainly determined by the orthorhombic-tetragonal (O-T) two-phase coexistence and grain size. Notably, a boosted dielectricity, ferroelectricity, and piezoelectricity accompanied by a raised TC is achieved at x = 0.10 mol%. Moreover, the highest TC∼125.40 ℃ is obtained at x = 0.40 mol% along with a degradation in dielectricity, ferroelectricity, and piezoelectricity. •O-T phase boundary is present in all samples at the vicinity of room temperature.•O-T phase boundary and grain growth contribute to piezoelectricity together.•First-principles calculations are used to reveal the inherent mechanisms.•Superior ferroelectricity Pr∼13.49 μC/cm2 is gained at x = 0.16 mol%.•An improved TC = 125.40 ℃ is obtained at x = 0.40 mol%.