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In this paper, barium ferrite powders were synthesized by sol-gel method, calcined at different temperatures, and on this basis the corresponding ceramics were prepared. The effects of calcination temperature on the structure, magnetic, dielectric and multiferroic properties of BaFe12O19 ceramics were studied. XRD results confirmed similarity between powders and ceramics, where dominant phase is BaFe12O19 and a small amount of an apparent BaFe2O4 impurity phase was formed at lower calcination temperature. The impurity BaFe2O4 phase is the main reason for decreasing powder magnetization. The maximum dielectric constant of 100 (at 10 kHz) and maximum remanent polarization, remanent magnetization and saturation magnetization of 0.46 μC/cm2, 47.37 emu/g and 79.96 emu/g, respectively, were obtained in the barium ferrite ceramics prepared from the powder calcined at 1100°C. This research could be the basis for the study of single-phase multiferroic materials and the development of multi-order electronic devices.

To address the current problem of low photoelectric conversion efficiency of BiFeO3 (BFO)-based photovoltaic (PV) devices, a TiO2/BFO core–shell nanowire array structure was constructed in this study based on the characteristics of excellent light reflection, stronger light-trapping effect, large specific surface area, fast transport rate of photogenerated carriers, and good energy band matching relationship. The TiO2/BFO core–shell nanowire arrays were prepared by the hydrothermal and sol–gel methods. The experimental results show that the light absorption performance of the TiO2/BFO core–shell nanowire arrays is significantly enhanced compared with the previously reported BFO-based ferroelectric photovoltaic (FEPV) films, and the conversion efficiency has significantly improved to 0.1177%. The intrinsic mechanism of PV enhancement of the designed TiO2/BFO core–shell nanowire array structure was illustrated by combining optical absorption, carrier lifetime, and energy band structure. This study further demonstrates the potential applications of transport material/ferroelectric material core–shell nanowire array structures in PV devices. [ABSTRACT FROM AUTHOR]

Magnetoelectric composites have attracted much attention due to their strong magnetoelectric coupling effect. In this paper, PbTiO3-NiFe2O4 (PTO/NFO) composite ceramics were prepared by sol-gel method. Effect of sintering temperatures on the structure, dielectric properties and multiferroic properties were studied. XRD results show that PTO/NFO ceramics have been successfully prepared. When the sintering temperature is 1050 °C, the secondary phase PbO2 exists in the ceramics. SEM results show that there were two kinds of grains with different sizes. EDS analysis suggested that the large particles are NFO and the small particles are PTO. The sintering temperature has a great influence on the dielectric and ferroelectric properties of the prepared ceramics. When the sintering temperature is 950 °C, the ceramics show the maximum dielectric constant at low frequency. When the sintering temperature is 1150 °C, the maximum residual polarization is 1.236 μC/cm2. The conductive mechanism of ceramics is dominated by Space Charge – Limited Conduction. The remanent magnetization and coercive field decrease with increasing the sintering temperature. The magnetoelectric coupling coefficient shows that ceramics have strong magnetoelectric coupling performance (5.7 V/cm·Oe). [ABSTRACT FROM AUTHOR]