Microstructure and dielectric properties of 0.99 (0.94Bi0.47Na0.47Ba0.06TiO3-0.06BiAlO3)-0.01NaNbO3 lead-free ceramics via different methods

In this work, 0.99(0.94Bi0.47Na0.47Ba0.06TiO3-0.06BiAlO3)-0.01NaNbO3 lead-free ceramics were synthesized by means of different methods including conventional solid state sintering (SSS), cold-sintering-assisted sintering (CSS), and spark plasma sintering (SPS) methods. Their microstructure and dielectric properties were studied comparatively. The ceramics via SPS and SSS exhibit pure structure, while a secondary phase exists in the ce-ramics via CSS. Compared to SSS, CSS and SPS can obviously reduce the processing temperatures for obtaining dense ceramics. The ceramics via SPS have the smallest mean grain size of 80 nm, while those via CSS and SSS exhibit increased grain sizes. The dielectric measurement demonstrates that temperature stability in dielectric constant at high temperatures is affected by sintering methods. The SPS sample shows the poorest temperature stability of permittivity. The ceramics post-annealed at 1050 degrees C via CSS exhibits the widest temperature range between 49 degrees C and 412 degrees C for temperature coefficient of capacitance <=+/- 15%, which can be expected to be used in the field of high-temperature capacitors.