Lead-free In₂O₃-doped (Bi_0.5Na_0.5)_0.93Ba_0.07TiO₃ ceramics synthesized by direct reaction sintering

Lead-free (Bi_0.5Na_0.5)_0.93Ba_0.07TiO₃–x wt %In₂O₃ ceramics synthesized by direct reaction sintering have been studied. X-ray diffraction reveals that all (Bi_0.5Na_0.5)_0.93Ba_0.07TiO₃–x wt %In₂O₃ ceramics are of a perovskite structure with coexistence of rhombohedral and tetragonal phases. It is found that the direct reaction sintering promotes growing of ceramic grains while doping of In₂O₃ contributes to inhibit and homogenize the grain growth, as shown by scanning electron microscopy. The ceramics show excellent piezoelectric and dielectric properties with thickness electromechanical coupling factor k_t=0.503, piezoelectric constant d₃₃=205 pC/N, dielectric constant ε₃₃^T/ε₀=1046, and loss tangent tan δ=0.036.