Achieving excellent temperature-stable dielectric properties of Bi_0.5Na_0.5TiO₃-based lead-free ceramics via doping AgNbO₃

The lead-free ceramics (1 - x)(0.94Bi(0.47)Na(0.47)Ba(0.06)TiO(3)-0.06BiAlO(3))-xAgNbO(3) (denoted as BNBTA-xAN) were synthesized via a solid-state sintering method. The effect of AgNbO3 doping amount on dielectric properties of the ceramics was studied systematically. X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscope were used to detect the structure of the ceramics. Temperature-dependent dielectric spectra, frequency-dependent dielectric constant and alternating current (ac) electric conductance at various temperatures were measured. The doping of AgNbO3 greatly reduces dielectric constant around Curie temperature and thus enhances the temperature stability of the dielectric constant. The ceramic BNBTA-0.03AN exhibits excellent temperature-stable dielectric properties with temperature coefficient of capacitance (TCC) <=+/- 15% between 55 degrees C and 418 degrees C with temperature window 363 degrees C and small changes of dielectric constant and dielectric loss from 100 Hz to 1 MHz at different temperatures. The obtained ceramics are expected to be used in high-temperature capacitors due to its excellent temperature stability.