The electrical properties of Ni_0.27Cu_0.10Zn_0.63Fe₂O₄ (NCZF) prepared from auto combustion synthesis of ferrite powders have been studied by impedance and modulus spectroscopy. We studied frequency and temperature dependencies of impedance and electric modulus of NCZF in a wide frequency range (20 Hz–5 MHz) at different measuring temperatures T _SM (30–225 °C). The complex impedance spectra clearly showed both grain and grain boundary effects on the electrical properties. The observed impedance spectra indicated that the magnitude of grain boundary resistance R _gb becomes more prominent compared to grain resistance R _b at room temperature, and with the increase in T _SM, R _gb decreases faster than the intrinsic R _b. The frequency response of the imaginary part of impedance showed relaxation behavior at every T _SM, and the relaxation frequency variation with T _SM appeared to be of Arrhenius nature and the activation energy has been estimated to be 0.37 eV. A complex modulus spectrum was used to understand the mechanism of the electrical transport process, which indicated that a non-Debye type of conductivity relaxation characterizes this material.

We have studied the optical, electronic and mechanical properties of Ni and Mn-doped CsGeCl₃ using DFT calculations.

Non-toxic (lead-free) inorganic perovskites have seized the leading position in the race for the commercialization of solar cells and other photovoltaic devices. The present study is the first theoretical approach to show that metal (Cr/Mn)-doped CsSnCl₃ perovskites exhibit high optical absorption, high photoconductivity, and high dielectric constant not only in the visible but also in the ultraviolet region of light energy due to the narrowing band gap. We carried out density functional theory (DFT) investigations to find the structural, electronic, optical, and mechanical properties of pristine CsSnCl₃, Cr-, and Mn-doped CsSnCl₃ samples in detail. The investigation of the optical functions displayed that the absorption edges of both Cr- and Mn-doped CsSnCl₃ shifted greatly in the direction of the low photon energy area (red-shift) compared with the pristine sample. An extra very high intensity peak of absorption was noted for both Cr- and Mn-doped CsSnCl₃ in the visible energy region. The investigation of the mechanical parameters revealed that both Cr- and Mn-doped CsSnCl₃ samples were as mechanically stable and highly ductile as the pure CsSnCl₃ sample. The investigation of the electronic properties demonstrated that the creation of intermediate states in the band gap for both the Cr- and Mn-doped CsSnCl₃ samples made the transition of excited photoelectrons to the conduction band from the valence band easier. A combined study suggested that Mn-doped CsSnCl₃ was better suited for applications in high potency solar cells and other optoelectronic devices than the other inorganic metal halide perovskites.

Spinel-type ferrites are widely used in practical applications. A fascinating property of Zn-Ni ferrites which reveals a direction for application is reported. A large negative magnetoresistance effect has been observed in ${\mathrm{ZnFe}}_2{\mathrm{O}}_4$ and Ni substituted ${\mathrm{Zn}}_{\text{1−x}}{\mathrm{Ni}}_x{\mathrm{Fe}}_2{\mathrm{O}}_4$ ferrites of spinel structure. These materials are either ferrimagnetic or paramagnetic at room temperature and a spin (cluster) glass transition was found for some compositions at low temperatures. The magnetoresistance is either parabolic or linear with respect to applied field up to 9 T depending on the compositions and temperatures. It was found that the magnetoresistance effect increases as the Ni content increases in ${\mathrm{Zn}}_{\text{1−}\mathrm{x}}{\mathrm{Ni}}_{\mathrm{x}}{\mathrm{Fe}}_2{\mathrm{O}}_4$ up to $\text{x=0.2}$ and then again decreases and finally become negligible for $\text{x=1.0,}$ i.e., ${\mathrm{NiFe}}_2{\mathrm{O}}_4.$ This magnetoresistance effect can be explained with the help of spin-dependent scattering and the Yafet-Kittel angle of the Ni-substituted Zn-Ni ferrites.

Structural, elastic and cation distribution properties have been investigated on stoichiometric and non-stoichiometric cobalt ferrites. Crystal structure, formation of spinel type ferrite, chemical bonding, cation distribution, and thermal properties of two series of Cr³⁺ substituted stoichiometric and non-stoichiometric various cobalt ferrites with general formula Co_1−xCr_xFe₂O₄ (S1), and Co_1+xCr_xFe_2−xO₄ (S2) were reported. Samples are synthesized by the solid-state reaction technique via planetary ball milling. X-ray diffraction (XRD) analysis confirms the formation of a single phase cubic spinel structure with the space group Fdm. Rietveld refinement results show that Cr occupies both the tetrahedral (A-site) and octahedral sites (B-site). The experimental lattice parameters show increasing trends for both the series with increase of Cr content. The cation–anion vacancies, chemical bonding, and the displacement of oxygen have been evaluated to understand the effect of Cr substitution and how the non-stoichiometry affects the physical and chemical properties of the material. The crystallite size is found to be the decreasing value with an increase of Cr concentration for both series of samples. Specific vibrational modes from the FTIR spectra suggest a gradual change of inversion of the ferrite lattice with the increase of Cr concentration which is also evident from Rietveld refinement data. The elastic properties analysis reveals that the synthesized samples for both series are ductile in nature. The non-stoichiometric structure with excess Co²⁺ may pave a new way to realize the lowering of Curie temperature of ferrite that is expected to improve the magnetocaloric properties.