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In this article, we present the results of low-temperature dielectric, magnetic and magnetodielectric properties of BiFeO3 nanoceramics prepared by auto-combustion method. Rietveld refinement results of X-ray diffraction data show that sample crystallizes in single-phase rhombohedral perovskite structure with R3c (No. 161) space group. The average crystallite size was found to be ≈ 600 Å from Williamson–Hall analysis. The temperature-dependent dielectric data have been presented in permittivity and modulus formalism to understand the relaxation dynamics. Three non-Debye-type relaxation processes were observed in the experimental window (173 to 423 K), which are explained using Kohlrausch–Williams–Watts (KWW) decay function. The temperature variation of relaxation times obeys Arrhenius's behaviour. The anomaly observed in the temperature dependence of relaxation times data near 240 K corresponds to the magnetic transition of BiFeO3. We found that single ionized oxygen vacancies with activation energy ranging from 0.4 to 0.8 eV are involved in the relaxation process. A crossover from AFM/PM to weak ferromagnetic ordering is observed at low temperature. The variation of capacitance with an applied magnetic field shows a hysteresis effect. The magnetocapacitance (MC%) changes by 3% at a magnetic field of 2 T for 200 kHz, indicating an intrinsic bulk magnetocapacitance effect in the ceramics. Hence, the above findings highlight the significance of the material as a potential candidate for device applications. [ABSTRACT FROM AUTHOR]

In this report, we have investigated the effect of BaTiO3 on the preliminary structural analysis, ferroelectric phase transition and electrical properties of (1 − x) P b (F e 0.5 N b 0.5 ) O 3 − x B a T i O 3 (P F N − B T) (x = 0 , 0.025 , 0.05, and 0.1) solid solutions. Conventional solid-state reaction technique is adopted to synthesize P F N − B T solid solution. X-ray diffraction (XRD) analysis is used to study the preliminary structural analysis, which suggests the formation of the single-phase materials. The surface morphology is studied using field emission scanning electron microscope (FESEM). The temperature-dependent dielectric properties display a broad diffuse phase transition from ferroelectric to paraelectric state and the phase transition temperature was found to be decreased with an increase in BT concentrations. Ferroelectric property of the solid solutions is confirmed by the polarization vs. electric field (P–E) loops study at room temperature. Variation of AC conductivity with frequency and temperature is also studied. The addition of BT leads to a decrease in the dielectric loss and phase transition temperature. [ABSTRACT FROM AUTHOR]

This manuscript presents a systematic study of conductivity and dielectric relaxations in the solid solution of (BiFeO3)1-x -(YMnO3)x for compositional range (0.0 ≤ x ≤ 0.2) as function of frequency, temperature, and magnetic field. The samples have been synthesized by combustion method. The thermal activations of dc-conductivity and relaxation time obey Arrhenius behavior for, x = 0.0, 0.025, 0.05 but follow variable range hopping of small polarons above, x ≥ 0.075 with activation energy 0.45 eV. The compositional time-temperature superposition of dielectric modulus data suggests that conduction mechanism changes with composition. The bulk capacitance decreases with increase in magnetic field. [ABSTRACT FROM AUTHOR]

This paper presents an advanced technique for calculating activation energy of oil-impregnated pressboard through dielectric response current measurement under switching impulse voltage at different temperatures. The proposed technique analyzes the measured impulse voltage and current signals to formulate its equivalent circuit at different temperatures. The equivalent circuit parameters are utilized to determine the shifting of ac conductivity curve along frequency axis with variations in temperatures. Based on the shifted ac conductivity curves at different temperatures, the corresponding activation energy of the insulation is estimated. The effectiveness of the proposed technique is investigated through a few laboratory prepared test samples. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile/functionalized single-walled carbon nanotubes (PAN/f-SWCNTs) nanocomposites were synthesized by an emulsifier-freein situpolymerization process. Interaction of polyacrylonitrile with functionalized single-walled carbon nanotubes was evidenced by ultraviolet-visible and Fourier transforms infrared spectroscopy. The structure and morphology of nanocomposites were characterized by X-ray diffraction, field emission scanning electron microscopy and high resolution transmission electron microscopy. Electrical conductivity was found to be increased by addition of f-SWCNTs. Thermogravimetric analysis study of PAN/f-SWCNT nanocomposites show more thermal resistance compared to the virgin PAN. The oxygen barrier property of PAN/f-SWCNT nanocomposites was reduced by eight times with increasing f-SWCNTs proportions. [ABSTRACT FROM PUBLISHER]

Abstract: A nanocomposite electrolyte comprising a polymer–salt complex (PEO25–NaClO4) and an organically modified sodium montmorillonite (Na-MMT) has been prepared using tape casting technique. The effect of clay concentration on structural, microstructural and electrical properties has been investigated. X-ray diffraction (XRD) analysis confirmed the formation and structure of the nanocomposite. FTIR analysis suggested a clear evidence of polymer–ion–clay interaction indicated by the changes appearing in the ν(ClO4 −) and ν(C–O–C) bands as a function of the clay concentration. The surface properties and microstructure has been studied using atomic force microscopy (AFM) technique. Complex impedance spectrum (CIS) shows the existence of bulk and grain boundary effects in the nanocomposite films. The temperature dependence of electrical conductivity obeys VTF pattern of variation. [Copyright &y& Elsevier]