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The range of working temperature in magnetocaloric effect has always been a concern for practical solid-state cooling applications. In this direction, the magnetocaloric effect analysis has been carried out in the composite of hard magnet Barium Hexaferrite and soft magnet Ni-Mn-Sn based Heusler alloy. This composite exhibits a constant high value of magnetic entropy changes with a large working temperature range near and above room temperature. On the other hand, magnetic biasing has been observed between the two magnetic phases in the composite. As a result, the tunable coercivity of the composite can be used in the recording media application. [ABSTRACT FROM AUTHOR]

The strong coupling of the spin and lattice subsystem exactly across the room-temperature region is observed in (MnNiSi)0.66(Fe2Ge)0.34 alloy which leads to a substantial change in magnetocaloric parameters. Substitution of Fe2Ge (Ni2In-type hexagonal symmetry) compound helps to distort the low temperature ferromagnetic phase and stabilize the high temperature paramagnetic phase near the room-temperature region. A large value of isothermal magnetic entropy change (ΔSM) of -13.67 J/kg-K at 300 K and relative cooling power (RCP) of 169.5 J/kg is observed for the (MnNiSi)0.66(Fe2Ge)0.34 alloy for a low magnetic field change of 30 kOe. Near room-temperature MST temperature and obtained large value of isothermal magnetic entropy change with large relative cooling power make the investigated (MnNiSi)0.66(Fe2Ge)0.34 alloy suitable for room-temperature solid state cooling applications. [ABSTRACT FROM AUTHOR]

Lead free NBT (sodium bismuth titanate) is an emerging ferroelectric material due to its ability to replace the lead based ceramics. In this work, the solid state reaction method is employed to prepare Sr modified Na0.5Bi0.5TiO3 (Na0.5Bi0.47Sr0.03TiO3). The structural, dielectric, ferroelectric, and optical properties have been investigated. The crystal symmetry has been identified from XRD and Raman spectra. The surface morphology of the prepared sample has been investigated from the FESEM micrograph. The average crystallite size is found to be 1.6 μm calculated by image J software. The frequency dependent dielectric properties of the sample has been studied in the range 10 Hz to 10 kHz. A wide optical bandgap (∼3.5 eV) of Na0.5Bi0.47Sr0.03TiO3 has been observed from the Tauc plot of UV spectra. [ABSTRACT FROM AUTHOR]

The nanocomposites of hard ferromagnetic BaFe12O19 and soft ferrimagnetic CuFe2O4 have been synthesized by the citrate sol-gel method which is calcined at different temperatures (800°C and 1000°C). The crystal structure, microstructural morphology, and magnetic properties were studied by employing the X-Ray Diffraction(XRD), Field- Emission Scanning Electron Microscopy(FE-SEM) and Vibrating Sample Magnetometer(VSM) techniques respectively. The exchange coupling of hard-soft magnetic nanocomposite materials have been explained by the “Henkel plot”. The nature of exchange interaction and magnetic dipole interaction of nanocomposites have been studied from δm vs H plots. This article gives the easy and inexpensive method for the preparation of hard-soft nanocomposites of magnetic materials and enhances its magnetic properties. [ABSTRACT FROM AUTHOR]

The nanocomposite of ferrites [(60%) BaFe12O19 + (40%) CoFe1.75 Zn0.25O4] has been prepared by the high energy ball milling method. The individual sample BHF (BaFe12O19) and CZF (CoFe1.75 Zn0.25 O4) are synthesized by the modified sol-gel method. The X-ray diffraction technique was employed to study the crystal structure of the sample. The maximum crystallite size of BHF and CZF are found to be 40±2 nm and 36±2 nm respectively in the composite which was annealed at 1000°C. The magnetic hysteresis (M-H) loop of nanocomposite has been recorded by the VSM (vibrational sample magnetometer) technique. The magnetic interaction between soft and hard magnetic phases is studied by plotting the graph between loop width (ΔH) verses magnetization (M). The loop width versus magnetization changes with the annealing temperature due to increase in the particle size. It is observed that there is an interaction between soft and hard magnetic phases. The M-H loops were recorded at different temperatures of sample prepared by the ball milling. Magnetic interaction between soft and hard magnetic phases at low temperature (60K) is different compare to that of room temperature. The maximum magnetic saturation (Ms) and coercivity (Hc) are found to be 77 emu/g and 3.8 kOe at 60K respectively. [ABSTRACT FROM AUTHOR]

Ferromagntic Fe2MnSi0.5Al0.5 heusler alloy has been studied here by analyzing its magnetic properties. To obtain the higher para to ferro magnetic transition temperature i.e. Curie temperature from the existing value of the parent compound, this particular compound has been chosen and, its critical exponent analysis has been done as there is no unique model for the 3d transition magnetic alloys to define their nature of phase transition. It has been observed that the material exhibit its Curie temperature at 225K and the Arrott plot technique employed here for obtaining Curie temperature also suggests that the magnetic phase transition observed here is of 2nd order. The critical exponent values 𝑖. 𝑒. 𝛽 = 0.49, 𝛾 = 1.001 𝑎𝑛𝑑 𝛿 = 3.04 are closely matching with theoretical Mean field value which indicates the existence of long range ferromagnetic ordering in the sample. [ABSTRACT FROM AUTHOR]

In the literature, it is found that the experimental value of saturation magnetization for Co2TiAl1-xSix (0≤x≤1) quaternary Heusler alloy is low compared to that of theoretical prediction by the Slater-Pauling rule. Hence, Co2TiAl0.75Si0.25 alloy has been prepared to enhance the saturation magnetization. The sample is characterized by the Xray diffraction technique and energy dispersive X-ray analysis. Magnetic hysteresis loops are recorded at different temperatures. Temperature dependence of magnetic saturation has been demonstrated by employing the Law of Approach (LA) to saturation and Bloch’s law at low temperature. Saturation magnetization at 0 K (extrapolated) has been found to be 1.09 µB/f.u.. However, anti-site disorder between Ti-Al and spin wave excitation at low temperature cause the reduction of the saturation magnetization at 0 K from the predicted value by the Slater- Pauling rule. [ABSTRACT FROM AUTHOR]

Lead free NBT (sodium bismuth titanate) is an emerging ferroelectric material due to its ability to replace the lead based ceramics. In this work, the solid state reaction method is employed to prepare Sr modified Na0.5Bi0.5TiO3 (Na0.5Bi0.47Sr0.03TiO3). The structural, dielectric, ferroelectric, and optical properties have been investigated. The crystal symmetry has been identified from XRD and Raman spectra. The surface morphology of the prepared sample has been investigated from the FESEM micrograph. The average crystallite size is found to be 1.6 μm calculated by image J software. The frequency dependent dielectric properties of the sample has been studied in the range 10 Hz to 10 kHz. A wide optical bandgap (∼3.5 eV) of Na0.5Bi0.47Sr0.03TiO3 has been observed from the Tauc plot of UV spectra. [ABSTRACT FROM AUTHOR]

The aluminium doped barium hexaferrite BaFe12-xAlxO19 with x =0.0, 1.0, 2.0, 4.0 and 6.0 have been synthesized by the sol-gel method to modify the magnetic properties for technological applications. The crystal structure and phase purity of all the samples have been explored by employing the X-ray diffraction (XRD) technique. It confirms that the sample is nanocrystalline, hexagonal symmetry and all the intense peaks could be indexed to the P63/mmc space group. The obtained lattice parameters from the XRD analysis decrease with the increase in Al3+ content in the samples. The microstructural morphology and particle sizes of all samples were studied by using the Field Emission Scanning Electron Microscopy (FESEM-Hitachi-S4800) technique. The magnetic hysteresis (M-H) loops measurement has been carried out at room temperature by employing the vibrating sample magnetometer (VSM) over a field range of +20 kOe to -20 kOe. The magnetic hysteresis (M-H) loops revealed the ferromagnetic (hard magnetic materials) nature of the samples and, analyzed by using the Law of Approach to Saturation. [ABSTRACT FROM AUTHOR]

Novel ceramic-polymer nanocomposites have great potential for electrical energy storage applications due to its high energy storage density. In the present work, BNT and PVDF based flexible polymer nanocomposites (BNT-PVDF) with different volume fraction (ϕ = 0, 5, 10, 15) were fabricated by solution casting method. Enhancement in beta phase of PVDF polymer matrix with the volume fraction (ϕ = 5, 10, 15) of BNT has been confirmed by X-ray diffraction (XRD) technique as well as Fourier transform infrared (FTIR) spectroscopy analysis. The enhancement of β phase increases as compared to (α) phases with volume fraction (ϕ) of nanofiller (BNT) in the matrix (PVDF) due to internal stress at the interface as well as structural modification of PVDF matrix. BNT-PVDF nanocomposites (with ϕ=10) showed a high dielectric constant (εr ≈ 78) relative to pure PVDF (εr ≈ 10) at 100 Hz. In addition to this, it exhibits relaxor type ferroelectric behavior with energy storage efficiency up to 77% for the volume fraction (ϕ) of 10. [ABSTRACT FROM AUTHOR]

Bi1-xLaxFe1-xMnxO3 ceramics with x = 0.00, 0.05, 0.10 and 0.20 were synthesized by the tartaric acid modified sol-gel technique with required optimization. The co-substitution suppresses the impurities phases in bismuth ferrite which is usually observed. It was observed that the composition-driven structural transition from rhombohedral (R3c space group) to orthorhombic symmetry (Pbnm space group) plays an important role in modifying the dielectric properties of bismuth ferrite. The dielectric constant was found to be increased in La and Mn co-substituted BiFeO3 due to significant large off-center movement of Fe3+ ions in the oxygen octahedra. The dispersion of dielectric constant in the frequency range of 100 Hz to 1 MHz has been analyzed by employing the modified Debye's function which suggests the contribution of multiple charge carriers in the dielectric relaxation. [ABSTRACT FROM AUTHOR]

To obtain the material with high dielectric constant and high dielectric strength for the technological applications, nanocomposite of Lanthanum Strontium Nickelete (La1.8Sr0.2NiO4) as nanofiller and polyvinylidene fluoride (PVDF) as polymer matrix has been prepared. The different nanofiler weight concentration varies from 2-8 weight percent. X-ray diffraction technique confirms the phase formation of nanocomposite. Differential scanning calorimeter (DSC) has been employed to study the percentage of crystallinity and Impedance measurement has been carried out to study the dielectric constant. DSC analysis shows decreasing trend of crystallinity whereas impedance analysis gives increasing dielectric constant with increasing La1.8Sr0.2NiO4 concentration in the nanocomposite. Also, these materials can be used as insulator in the transformer as the strength and dielectric behavior of present composite meets the technological requirements. [ABSTRACT FROM AUTHOR]

(1-x)Cobalt ferrite-(x)reduced graphene oxidenanocomposites with x=0, 0.1, 0.2 and 0.3 were prepared by the ultrasonic method. The crystal symmetry modification due to reduced graphene oxide and cobalt ferrite interaction has been studied by employing the X-ray diffraction technique. Morphology of the samples was studied by the Field emission scanning electron microscopy (FE-SEM). Study on electrical properties of the cobalt ferrite-reduced graphene oxide nanocomposites explores the possible application of these composites as anode material. Impedance decreases with an increase in frequency as well as temperature, which supports an increase in ac electrical conductivity. The modified Debye relaxation model can explain the behavior of impedance in cobalt ferrite-reduced graphene oxide nanocomposites. [ABSTRACT FROM AUTHOR]

The sol gel technique was used to prepare Pb1-xNdx Zr0.52Ti0.48O3 with x = 0.02, 0.04, 0.06 and 0.10 samples. Room temperature Raman spectra of all the sample were recorded in the range of wave number 30-1000 cm-1. It suggests that the increase in contribution of tetragonal crystallographic phase with the increase in Nd concentration in the sample. FTIR study shows the presence of characteristic bending and streching vibrations of perovskite (ABO3) structure. Ferroelectric and piezoelectric properties were enhanced by the Nd substitution at Pb site of PbZr0.52Ti0.48O3. [ABSTRACT FROM AUTHOR]

Co1-xSrxFe2-xTixO4 (x= 0.01, 0.05, 0.1, 0.15, 0.2) has been synthesized using the sol-gel technique. The phase purity of the material has been studied by employing the X-ray powder diffraction (XRD) technique. The obtained XRD pattern shows the characteristic of Fd3m space group in cubic symmetry. The magnetic hysteresis loop has been recorded using vibrating sample magnetometer (VSM) at room temperature in the field range of ±2T. The loop has been studied using Law of Approach (LA) to saturation to calculate magnetocrystalline anisotropy. The magnetocrystalline anisotropy and saturation magnetization decrease with increase in doping concentration. Competition between strain mediated magnetism and magnetism due to superexchange interactions between cations has been observed. [ABSTRACT FROM AUTHOR]

The PVDF-CoFe1.5Cr0.5O4 (PVDF-CFCO5) nanocomposite films are synthesized with different weight % of CoFe1.5Cr0.5O4 as filler in PVDF matrix. X-ray diffraction pattern detected the existence of α and β phases and, also validate the result by Fourier transform infrared microscopy. The inclusion of CFCO5 nanoparticles in the polymer medium initiates the alteration of phase between α and β and, offers the nanocomposites greater mobile charge carriers which contribute in the interfacial polarization. The dielectric properties of PVDF-CFCO5 films have superior dielectric constant and considerably a lesser dissipation factor (tan δ) as compared to pure PVDF as well as pure cobalt ferrite. The dielectric constant decreases at higher concentrations of CFCO5 due to agglomeration of the nanoparticles. Thus, their controlled inclusion in a polymer medium to get improved electrical properties will have a significant impact to the present day research. The enhanced dielectric constant of PVDF-CFCO5 film can be utilized for wide applications such as dielectric material for capacitor application. [ABSTRACT FROM AUTHOR]

Role of grain and grain boundary on electrical and thermal conductivity of Bi0.9Y0.1Fe0.9Mn0.1O3 ceramic was investigated systematically. Tartaric acid modified sol gel method was used to synthesize the compound. X-ray diffraction technique was used to confirm the formation of single phase orthorhombic (Pbnm) structure. Electrical properties of the sample were measured with a wide frequency range from 100Hz to 10MHz at different temperature from 40°C to 250°C. AC impedance studies indicate the presence of grain and grain boundary effect. The negative temperature coefficient of resistance (NTCR) behaviour of the compound has been confirmed by the cole-cole plot. DC electrical and thermal conductivities of the compound were explained on the basis of grain and grain boundaries. [ABSTRACT FROM AUTHOR]

Cobalt ferrite of different average crystallites (from nanocrystallite to micro crystallites) has been prepared by the Sol-Gel Method. The X-ray diffraction (XRD) analysis confirms the cubic spinel phase with no trace of impurity phases. The effect of annealing temperature on micro structure and electric transport properties as a function of frequency and temperature has been studied. It is observed that the electric impedance and conductivity are strongly dependent on grain size. The impedance spectroscopic study is employed to understand the electrical transport properties of cobalt ferrite. [ABSTRACT FROM AUTHOR]

The compositional driven crystallographic phase transition and its effect on the dielectric constant have been investigated on Nd and Mn Co-substituted BiFeO3 Ceramics. The distinct changes in phonon modes of Raman spectra and transmission band of FT-IR show the evidence for structural transition (rhombohederal (R3c) to orthorhombic orthorhombic (Pbnm)) with the increase in the substitution concentration. The dielectric constant was found to increase by significant magnitude with the increase in substitution concentration of Nd and Mn around morphotropic phase Boundary (7.5 % of co-substitution) due to increase in the off-centre movement of Fe3+ ions and Bi3+ in the oxygen octahedra and cuboctahedra respectively. [ABSTRACT FROM AUTHOR]

Effect of lattice distortion on diffuse phase transition in BNBTO solid solutions near Morphotropic phase boundary (MPB) has been investigated. Solid solutions of (Bi0.5Na0.5)1−xBaxTiO3 (with mole % of x= 0.04, 0.05, 0.06, 0.07 and 0.08) were prepared by the planetary ball mill method in ethanol medium. Rietveld refinement technique with rhombohedral (R3c) and tetragonal (P4bm) crystal symmetry has been employed for structural as well as phase analysis of the solid solutions. Both rhombohedral and tetragonal lattice distortion (c/a) tends toward the pseudo-cubic crystal symmetry with the increase of mole fraction of Ba2+ near MPB (x= 6 mole %). Also, the average crystallite size and grain size decrease with increase of mole fraction of Ba2+ in BNT ceramic are due to larger ionic radius of Ba2+ and grain boundary pinning process in the solid solutions respectively. Additionally, depolarization temperature (Td) and maximum temperature (Tm) reduces due to the lattice distortion of both the phases in BNBTO solid solutions, which is explained extensively. Significant increase of dielectric constant has been observed near MPB composition (x=6%) in BNBTO solid solutions. [ABSTRACT FROM AUTHOR]

Magnesium substituted lead zirconate titanate Pb1-xMgxZr0.52Ti0.48O3 (x=0.02, 0.04, 0.06 & 0.08) have been prepared by the sol-gel method. The crystal structure and phase purity of the samples were studied by powder X-ray diffraction (XRD) technique. The ferroelectric hysteresis loop measurements were carried out at room temperature using ferroelectric loop tracer over a field range of 4.5kv/cm. The saturation polarization and coercivety and remnant polarization increase with the increase in magnesium concentration. The piezoelectric constant was measured by varying the polling field was found to be decrease with the increase in concentration of magnesium. [ABSTRACT FROM AUTHOR]

Lanthanum and titanium doped BiFeO3 ceramics Bi1-xLaxFe1-xTixO3 (x&0.0, 0.03 & 0.06) were synthesized by using the Sol-gel method. The phase purity has been studied by powder X-ray diffraction technique. No secondary phases were evident after lanthanum and titanium addition in certain proportion. The XRD patterns have been analyzed by employing Rietveld refinement technique with the help of Fullprof program. The XRD pattern could be refined by R3c space group in rhombohedral symmetry. The electrical characteristics for all samples have been studied by ferroelectric hysteresis loop at room temperature in the applied electric field of 60 kV/cm. [ABSTRACT FROM AUTHOR]

Bi1-xLaxFe1-xMnxO3 ceramics with x = 0.00, 0.05, 0.10 and 0.20 were synthesized by the tartaric acid modified sol-gel technique with required optimization. The co-substitution suppresses the impurities phases in bismuth ferrite which is usually observed. It was observed that the composition-driven structural transition from rhombohedral (R3c space group) to orthorhombic symmetry (Pbnm space group) plays an important role in modifying the dielectric properties of bismuth ferrite. The dielectric constant was found to be increased in La and Mn co-substituted BiFeO3 due to significant large off-center movement of Fe3+ ions in the oxygen octahedra. The dispersion of dielectric constant in the frequency range of 100 Hz to 1 MHz has been analyzed by employing the modified Debye's function which suggests the contribution of multiple charge carriers in the dielectric relaxation. [ABSTRACT FROM AUTHOR]