Effects of CaTiO3, BaTiO3, and BaZrO3 on the crystal structures and electrical properties of Bi1/2Na1/2TiO3–SrTiO3 piezoelectric ceramics

This study investigated the effects of CaTiO3, BaTiO3, and BaZrO3 doping on the phase transition and strain properties of lead-free 0.76Bi1/2Na1/2TiO3-0.24SrTiO3 (BNT-24ST) piezoceramics. The nonergodicity of the BNT-24ST ceramic was stabilized as a function of CaTiO3 doping, corresponding to the existence of the ferroelectric-to-relaxor phase transition temperature (TF-R) peak in the dielectric permittivity curves of the samples. However, the BaTiO3- or BaZrO3- doped NBT-24ST samples promote the transition from a nonergodic to an ergodic relaxor phase. The 0.01 mol BaTiO3 or 0.01 mol BaZrO3 doping decreases the TF-R peak of the NBT-24ST sample to below room temperature. Interestingly, it is noted that the nonergodic-to-ergodic relaxor phase transition of the BaTiO3-doped BNT-24ST ceramics was faster than that of the BaZrO3-doped BNT-24ST ceramics. The 0.01 mol BaTiO3-doped BNT-24ST sample presents a maximum dielectric constant of 8000. The maximum piezoelectric actuator coefficient (uni-Smax/Emax) of 525 pm/V was observed for the 0.01 mol BaTiO3-doped BNT-24ST ceramic. The effect of the tolerance factor on the phase transition and electrical properties of the BNT-24ST-ABO3 ceramics is suggested.