Low temperature sintering of iron-barium co-doping bismuth sodium titanate lead free piezoelectric

This work reports a detailed study of the crystal structure and electrical properties of a potential lead-free piezoelectric Bi0.5Na0.5TiO3 co-doped with Ba2+ and Fe3+ sintered at relatively low temperature (900 °C). The effect that co-dopants have over the electric properties in (Bi0.5Na0.5)1-xBaxTi1-yFeyO3-0.5y, varying x from 0 to 0.075, x=0.025, and y from 0 to 0.075, y=0.025, was evaluated. XRD analysis showed a successful synthesis of co-doped BNT ceramics with a rhombohedral structure for samples with x < 0.075. In contrast, the sample with x = 0.075 exhibited the coexistence of the rhombohedral and tetragonal structures, confirmed by Rietveld refinement. The co-doping promotes the grain size growth and increase the pellets’ density from 93% to 98%. Dielectric spectroscopy analysis, conducted in the range from 25 to 500 °C, showed an increase in the relative permittivity with the dopant concentration, specifically at high temperatures. Electric analysis validate the piezoelectric behavior and the electric polarization of the co-doped BNT ceramics, unveiling a maximum remnant polarization (Pr) of 25.6 µC/cm2 and, a maximum piezoelectricity coefficient of 53 pC/N, which varied depending on the composition. The obtained results demonstrate that co-doping BNT ceramics with Ba2+ and Fe3+ cations lower the sintering temperature typically used in the solid-state reaction to obtain pure BNT, showing similar properties compared to those of the same material sintered at higher temperatures and longer times.