Effect of SrTi0.875Nb0.1O3 Doping on Energy Storage Density of Lead-fFee Bi0.5Na0.5TiO3-BaTiO3 Based Piezoelectric Ceramics

Abstract

Lead-free piezoelectric ceramic of (0.94-x)[(Bi_0.5Na_0.5)TiO₃] + 0.06BaTiO₃ + xSrTi_0.875Nb_0.1O₃ (abbreviated as BNBT-xSTN) with x equal 0.0, 0.1, 0.2, 0.3, and 0.4 were synthesized using solid state reaction. The mixing of raw materials was ball milled in alcohol for 24 hours and then calcined at 850 ^oC for 2 hours to form BNBT-xSTN powder. The BNBT-xSTN powders were further shaped and sintered at 1175 °C with a heating rate of 5 °C per minute and held at the sintering temperature for 2 hours. The crystal structure, microstructure, dielectric, ferroelectric, strain, and energy storage density of the BNBT-xSTN ceramics were systematically investigated. The BNBT-xSTN ceramic materials were analyzed using X-ray diffraction (XRD), all samples show a typical perovskite structure without any trace of secondary phase with a crystal structure coexisting in rhombohedral and tetragonal phases (R&T). Scanning electron microscopy (SEM) images showed the grain boundaries and porosity. The highest dielectric constant was 2511 at x equal 0.2. On the other hand, polarization and strain of STN doped on BNBT were induced with various electric fields E equal 40 to 60 kV/cm, the electric field-induced strain curves of the analyzed samples show a phase transition from a ferroelectric phase to a relaxor phase when the STN is doped. The x equal 0.1 sample showed the maximum energy storage density of 0.3 J/cm³ at E equal 60 kV/cm, corresponding to the W_rec/E_max value of approximately 5 × 10^{- 3} J/(kV.cm²).