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

Large energy storage density and big electrocaloric strength in the BiFeO3–BaTiO3 system.

Hot pressing process ameliorates internal defects of PBZ/PVDF composite film for a high electrocaloric effect near room temperature

The poor interface compatibility between inorganic fillers and organic polymer matrix in nanocomposite has presented considerable challenges, which limit the applicable electric field ranges and reduce the interface polarization interaction. In this paper, Pb[Formula: see text]Ba[Formula: see text]ZrO3 (PBZ) nanofibers were introduced into the polyvinylidene fluoride (PVDF) matrix to prepare composite film, and the effect of hot pressing on interface compatibility was investigated at volume composite ratios of 3% and 4%. For the untreated film, [Formula: see text] and [Formula: see text] of the 3 vol.% composite film are 9.68 [Formula: see text]C/cm2 and 401 MV/m, respectively, and those for the 4 vol.% composite film are 9.15 [Formula: see text]C/cm2 and 408 MV/m, respectively. These differences are mainly due to the impact of internal defects. After hot pressing, [Formula: see text] and [Formula: see text] for the 3 vol.% composite film became 10.22 [Formula: see text]C/cm2 and 490 MV/m, respectively. Those for the 4 vol.% composite film are 9.85 [Formula: see text]C/cm2 and 485 MV/m. Experiment and simulation results showed the beneficial effect of hot pressing, which ameliorated poor interfacial compatibility, reduced internal defects, and improved the crystallinity of the composite film. A high electrocaloric effect (ECE) was obtained by using the direct measure method. At −30[Formula: see text]C, the [Formula: see text] values of hot-pressed PBZ/PVDF film at 3[Formula: see text] and 4[Formula: see text] vol.% were 23.81 and 19.73 K, respectively. When temperature increased to 70[Formula: see text]C, the [Formula: see text] values were 9.44 and 7.01 K, respectively, which were 1.58 times of the values of a non-hot-pressed film. These results indicated that hot pressing alleviated the interface problem and resulted in high EC performance under a high-strength electric field.