Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

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Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Electrical characterizations of Nb2O5 doped 0.65BiFeO3–0.35BaTiO3 (0.65BF–0.35BT) ceramic were carried out over broad temperature and frequency ranges through dielectric spectroscopy, impedance spectroscopy, and ac conductivity measurements. The dielectric constant and loss tangent are drastically reduced with introducing Nb2O5 into the 0.65BF–0.35BT system. Two dielectric anomalies are detected in the temperature regions of 100 °C ≤ T ≤ 280 °C and 350 °C ≤ T ≤ 480 °C, and the Curie temperature (TC) was confirmed in higher temperature region. A dielectric relaxation with large dielectric constants was detected near the TC. This dielectric relaxation becomes even stronger with the gradual increase in the Nb2O5 content. Impedance spectroscopy results clearly show the contributions of grains and grain boundaries in the frequency range of 100 Hz ≤ f ≤ 1 MHz, and the relaxation processes for grains and grain boundaries are non-Debye-type. The grain boundaries are more resistive than that of the grains, revealing the inhomogeneity in samples. The experimental results are well fitted based on a Maxwell-Wagner (MW) interfacial polarization model below 100 kHz, and the MW interfacial polarization effect becomes more and more obvious with the increase in the Nb2O5 content. The increase in dielectric constant is possibly related to space charge polarization, which is caused by charges accumulated at the interface between the grain and grain boundaries. Frequency dependence of the ac conductivity confirms the MW interfacial polarization effect below 100 kHz.

Dielectric relaxation and Maxwell-Wagner interface polarization in Nb2O5 doped 0.65BiFeO3–0.35BaTiO3 ceramics

A previous study of the growth conditions has shown that single-phase BiFeO3 thin films can only be obtained in a narrow pressure-temperature window and that these films display a weak magnetic moment. Here we study in more detail the structure and the magnetism of single-phase BiFeO3 films by means of reciprocal space mapping, Raman spectroscopy and neutron diffraction. X-ray and Raman data suggest that the BiFeO3 structure is tetragonal for 70 nm-thick films and changes to monoclinic for 240 nm-thick films, thus remaining different from that of the bulk (rhombohedral) structure. In the 240 nm monoclinically distorted film neutron diffraction experiments allow the observation of a G-type antiferromagnetic order as in bulk single crystals. However, the satellite peaks associated with the long-wavelength cycloid present in bulk BiFeO3 are not observed. The relevance of these findings for the exploitation of the magnetoelectric properties of BiFeO3 is discussed.

Structural distortion and magnetism of BiFeO3 epitaxial thin films: a Raman spectroscopy and neutron diffraction study

Microstructure and ferroelectric properties of Nb2O5-modified BiFeO3-BaTiO3 lead-free ceramics for energy storage

An optimized lead-free formamidinium Sn-based perovskite solar cell design for high power conversion efficiency by SCAPS simulation

Evidences of magneto-electric coupling in BFO–BT solid solutions

Impedance spectroscopy and conductivity analysis of multiferroic BFO–BT solid solutions

Effects of Sb, Zn doping on structural, electrical and optical properties of SnO2 thin films

The present study pertains to magnetoelectric coupling and energy storage analysis of (1 − x)BiFe0.95Mn0.05O3-xBaTiO3 (BFMO-BT) with x = 0.1, 0.2, 0.3 lead free solid solutions. BFMO-BT solid solutions possessed a cubic structure as confirmed from powder XRD and the Rietveld refinement. A maximum ferroelectric polarization of 0.82 μC/cm2 was observed in BFMO-0.3BT. BFMO-0.3BT exhibited a maximum energy storage density (WU) of 1.97 J/cm3 and an energy conversion efficiency of 81.7%. Enhanced bulk magnetization was associated with the lattice defects; however, it decreased with increased BT content. For BFMO-0.3BT, temperature dependent susceptibility, dielectric measurement, and differential scanning calorimetry measurement revealed the magnetic transition temperature to be 275 °C, 293 °C, and 223 °C, respectively. The linear magnetoelectric coupling coefficient was measured by quantifying change in maximum polarization with respect to the applied magnetic field and was found to be 28.55 mV cm−1 Oe for BFMO-0.3BT. Conductivity measurements of BFMO-0.3BT revealed a maximum value of activation energy, i.e., 0.21 eV at 1 kHz.

Manish Kumar

Papers

An optimized lead-free formamidinium Sn-based perovskite solar cell design for high power conversion efficiency by SCAPS simulation

Evidences of magneto-electric coupling in BFO–BT solid solutions

Impedance spectroscopy and conductivity analysis of multiferroic BFO–BT solid solutions

Effects of Sb, Zn doping on structural, electrical and optical properties of SnO2 thin films

Enhanced magneto-electric coupling and energy storage analysis in Mn-modified lead free BiFeO3-BaTiO3 solid solutions