Large energy-storage density and positive electrocaloric effect in xBiFeO3-(1-x)BaTiO3 relaxor ferroelectric ceramics

xBiFeO(3)-(1 - x)BaTiO3 relaxor ferroelectric ceramics were synthesized via the high-temperature solid-state reaction process. The X-ray diffraction patterns of xBiFeO(3)-(1 - x)BaTiO3 showed that the structure of samples was transformed from the tetragonal phase to the pseudo-cubic phase when x >= 0.025. The calculated universal Curie-Weiss constants and slim shape of the polarization-electric field hysteresis loops indicated that xBiFeO(3)-(1 - x)BaTiO3 ceramic was converted from a normal ferroelectric to a relaxor ferroelectric. The energy-storage properties of 0.1BiFeO(3)-0.9BaTiO(3) were also measured at room temperature. The maximum discharged energy density and efficiency procured were 1.22 J cm(-3) and 85.98%, respectively. The electric field-dependent energy-storage density was fitted using an exponential function of E-n, and it was found that n < 2. It was worth noting that the positive electrocaloric effect (ECE) was observed in xBiFeO(3)-(1 - x)BaTiO3 bulk ceramics, no matter when directly measured using a thermocouple or indirectly calculated using the Maxwell relation. Also, a Delta T-max of 1.55 K was indirectly calculated from the temperature-dependent P-E hysteresis loops for 0.05BiFeO(3)-0.95BaTiO(3); while a Delta T-max of 2.20 K was directly obtained using the thermocouple. The positive ECE means that the xBiFeO(3)-(1 - x)BaTiO3 is a conventional ferroelectric or relaxor ferroelectric. Finally, the electrocaloric strengths measured were considered with the equation dT/dE obtained by Lu et al.

Automated summary

xBiFeO(3)-(1 - x)BaTiO3 relaxor ferroelectric ceramics were synthesized via a high-temperature solid-state reaction process. The structure of the samples transformed from tetragonal phase to pseudo-cubic phase when x >= 0.025. The ceramics exhibited positive electric-field dependent energy-storage density and a positive electrocaloric effect.