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In this paper, xPbTiO3/(1-x)NiFe2O4 (PTO/NFO, x = 0.1, 0.2, 0.3, 0.4 and 0.5) ceramic composites were prepared by mixing of sol-gel synthesized PTO and NFO powders, followed by their uniaxial pressing and sintering at 1150 °C. The effects of PTO/NFO composition on crystal structure, surface morphology, electrical, magnetic and magnetoelectric coupling properties were studied. XRD results showed that the prepared ceramics contain only PTO and NFO phases without any impurity phase. The samples were relatively dense while the grains were evenly distributed. The dielectric constant and loss varied monotonically with the frequency for different molar ratios. The hysteresis loop of the composites with high amount of high resistance NFO phase (x = 0.1, 0.2) has the shape characteristic for a material with large leakage current. The samples with x = 0.1 showed the largest saturated magnetization, while the sample with x = 0.2 had the maximum remnant magnetization. It was also shown that the polarization was affected by the external magnetic field of 1 mT and the strongest ME coupling (relative polarization change of 15.4%) was observed for the 0.5PbTiO3/0.5NiFe2O4 composite. In addition, the relevant calculation showed that the leakage mechanism may not be the main factor affecting the polarization of the obtained ceramics.

Co0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 (CZFO/BST) composite ceramics with different molar ratios (1:3, 1:2, 1:1, 2:1 and 3:1) were prepared by combining chemical co-precipitation and sol-gel method. Effects of molar ratio on the microstructure, dielectric and multiferroic properties were investigated. The formation of the individual phases and the composites was confirmed by XRD results and small amount of secondary phase (Ba2Fe2Ti4O13) was observed. The grain sizes of magnetic (CZFO) and ferroelectric phase (BST), measured by SEM, were about 5 µm and 0.5 µm, respectively. The sample with molar ratio (1:2) has the largest dielectric constant, while the sample with molar ratio (3:1) shows the lowest dielectric constant. A distinct loss peak can be observed for all the samples. Both the peak position and peak intensity increase with the frequency, indicating relaxation polarization process generated by space charge or interface polarization. The ceramics with molar ratio (1:1) shows the smallest leakage current (∼ 10−7 A/cm at 1.5 kV/cm), while the leakage current (∼ 10−5 A/cm at 1.5 kV/cm) of the sample with molar ratio (3:1) is the largest. The ferroelectric hysteresis loop is not apparent due to the low Curie temperature of the ferroelectric phase, but the sample with molar ratio (2:1) shows the best ferroelectric properties. It was found that with the increase of CZFO content, the values of saturation (Ms) and remnant (Mr) magnetization increase at first and then decrease. The sample with molar ratio (3:1) has the maximum Ms value (about 50.34 emu/g), while the sample with molar ratio (1:2) shows the minimal Mr value (about 0.46 emu/g). This anomalous magnetic property is induced by the interface interaction between the two phases.

Organic–inorganic hybrid perovskites with 3D perovskite structure have gained much attention as light harvesting materials in thin-film photovoltaics. This is because of their outstanding light-absorption characteristics, charge-transport dynamics and their simple processability using lab-scale solution and vapor phase deposition techniques. However, the inherent instability and lead toxicity of lead-based PSCs are the major problems at present. Recent studies have shown that the (CH3NH3)3Bi2I9 (MBI) 0D bismuth-based compound can be used as an optical absorption layer in solar cells. In this paper, the (CH3NH3)3Bi2I9 was doped with Cl− and a series of (CH3NH3)3Bi2I9−xClx films were prepared. The effects of different doping amounts on the microstructure, photovoltaic properties and ferroelectric properties were systematically investigated. Scanning electron microscope (SEM) and Atomic force microscope (AFM) analysis showed that with the increase of doping content, the density of the films increased and the roughness decreased. The photoelectric conversion efficiency of (CH3NH3)3Bi2I9−xClx raises with the increase of doping content. For example, the photoelectric conversion efficiency of (CH3NH3)3Bi2I3Cl6 is 0.473%. We find that the leakage current descends into the increase in doping content, which may be due to the increase in the film density and the decrease of porosity. These research results have a positive effect on the development of Bi-based lead-free perovskite.