High-temperature stability of dielectric and energy-storage properties of weakly-coupled relaxor (1-x)BaTiO3-xBi(Y1/3Ti1/2)O3 ceramics

Lead-free (1-x)BaTiO3-xBi(Y1/3Ti1/2)O3 ceramics (abbr. (1-x)BT-xBYT) were synthesized via a solid state process. X-ray diffraction (XRD) measurements and Raman spectra reveal that, for x > 0.05, the ceramics structure changes from a ferroelectric tetragonal to a pseudo-cubic phase at room temperature. Dielectric tests indicate that the ceramics exhibit a relaxor behavior, the temperature (Tm) at which the maximum dielectric constant (epsilon m) is obtained shifts towards lower values. As the BYT content increases, the dielectric dispersion factor (gamma) increases from 0.99 to 1.86, the temperature coefficient of permittivity (TC epsilon) decreases to -60 ppm/degrees C, and the capacitance variation is within temperature coefficient of capacitance (TCC) <= 15% in the temperature range from RT to 400 degrees C (x = 0.20). Furthermore, as the BYT content increases, high polarization maxima (Pmax), low remnant polarization (Pr), and slim P-E hysteresis loops can be observed. An energy storage density (Wrec) of 1.02 J/cm3 and energy efficiency (eta) of 78% were achieved for x = 0.15, while these amounted to 0.77 J/cm3 and 90% for x = 0.2. Moreover, good temperature stability of energy storage properties is also obtained. These results indicate that the as-synthesized (1-x)BT-xBYT ceramics are potential lead-free materials for energy storage applications.