Manoranjan Kar

Rietveld analysis of XRD patterns of different sizes of nanocrystalline cobalt ferrite

Nanocrystalline cobalt ferrite powder has been synthesised by citrate precursor and co-precipitation methods. Structural characterization of the samples has been carried out using powder X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscope (FE-SEM). Distribution of cations among the two interstitial sites (tetrahedral and octahedral sites) has been estimated by analysing the powder X-ray diffraction patterns by employing Rietveld refinement technique, and the results reveal the existence of samples as a mixed type spinel with cubic structure. It is observed that the distribution of cations and structural parameters are strongly dependent on synthesis method and annealing temperature. The vibrational modes of the octahedral and tetrahedral metal complex in the sample have been examined using FT-IR in the wave number range of 390 to 750 cm−1, and it shows an absorption band within this range, which confirms the spinel structure of the sample. The existence of constituents in the sample, i.e., Co, Fe and O has been authenticated using energy dispersive spectrum with the help of a FE-SEM.

Existence of multi crystallographic phase in BNT-BTO solid solution near morphotropic phase boundary (MPB)

Lead free Bismuth sodium titanate (BNT) base solid solutions are focusing intensively due to their potential applications as an alternative for Pb-base compounds. In this work, Solid solutions of BNT and barium titanate [(1-x) BNT + x BTO with x=0.00, 0.06, 1.00] have been prepared via conventional solid state route by using the planetary ball mill method. Crystallinity of the samples characterized by XRD and various structural parameters are calculated by employing Rietveld refinement technique. The distinct peak (002/200) splitting around 460 to 470 confirmed the presence of both rhombohedral and tetragonal phase in the solid solution. Dielectric constant of the solid solution near the morphotropic phase boundary (x= 0.06) is significantly enhanced as compared to BNT and BTO. The electrical conductivity of the solid solution was found to reduce w.r.t to BNT. The above results indicate the possible application of BNT-BTO solid solution near MPB in the field of energy storage.

Effect of strontium substitution on dielectric constants of PZT nanocrystalline ceramics

The influence of soft isovalent doping at Pb2+ site of PZT had been extensively investigated for various specific properties required in either thin films or bulk ceramics. In this report, we have studied the influence of isovalent Sr2+ substitution on A site of PZT on dielectric constant and impedance spectroscopy. The samples with the stoichiometry Pb1-xSrx(Zr0.52Ti0.48)O3, x = 0.02, 0.06 & 0.1 were synthesized by the sol gel method. Temperature dependent dielectric study has been carried out in the temperature range of 35 °C to 450 °C. The impedance study shows NTCR properties in the sample.

Nanostructured zinc oxide as a prospective room temperature thermoelectric material

Nanostructured Zinc oxide (ZnO) was synthesized via a ball milling for 10 hours using high energy planetary ball mill. Phase purity and homogeneity of all the samples have been investigated by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). All the diffraction peaks can be indexed to the hexagonal phase ZnO with hexagonal symmetry (space group P63mc). Average crystallite size was observed to be 20 nm. There was a remarkable suppression in thermal conductivity (κ) compared to the bulk values by a factor of ∼50 at room temperature. This suggests to the possibility of using nanostructured ZnO as a prospective room temperature thermoelectric material.

Enhance of ferroelectric properties by modifying Pb2+ side by Mg2+ in PZT (52/48) ceramics

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.

Effect of excess bismuth on synthesis of bismuth ferrite

BiFeO3 ceramics were prepared by using the sol-gel technique with adding excess amount of bismuth. Different concentrations of excess bismuth were used to study the evolution of crystal structure and physical properties of BiFeO3. The phase purity and crystal structure of all samples have been studied by powder X-ray diffraction. The primary BiFeO3 phase could be indexed to R3C space group and analyzed by Rietveld method to extract different crystallographic parameters. Secondary phases were suppressed with addition of 4% excess bismuth. The leakage current for all the samples for all samples have been studied by ferroelectric hysteresis loop at room temperature in the maximum electric field of ±100 kV/cm. The leakage current for 4% sample is least (1.86 nA) among all samples due to reduction of extra phases.

Crystal structure and magnetic properties of Cr doped barium hexaferrite

The Cr3+ substituted BaFe12O19 has been synthesized by modified sol-gel method to tailor the magnetic anisotropy and coercivity for technological applications. Some basic studies have revealed that this substitution leads to unusual interactions among the magnetic sublattices of the M-type hexaferrite. In order to investigate these interactions, BaFe12-xCrxO19 (x = 0.0, 0.5, 1.0, 2.0, and 4.0) M-type hexaferrites were characterized by employing XRD (X-ray Diffractometer). It is confirmed that, all the samples are in nanocrystalline and single phase, no impurity has been detected within the XRD limit. The magnetic hysteresis (m-H) loops revealed the ferromagnetic nature of nanoparticles (NPs). The coercive field were increasing with the increasing Cr3+ content, but after the percolation limit it decreases. The magnetocrystalline anisotropy is increasing with the Cr3+ concentration in samples and high values of magnetocrystalline anisotropy revealed that all samples are hard magnetic materials. Magnetic hysteresis loops were analyzed using the Law of Approach to Saturation method.The Cr3+ substituted BaFe12O19 has been synthesized by modified sol-gel method to tailor the magnetic anisotropy and coercivity for technological applications. Some basic studies have revealed that this substitution leads to unusual interactions among the magnetic sublattices of the M-type hexaferrite. In order to investigate these interactions, BaFe12-xCrxO19 (x = 0.0, 0.5, 1.0, 2.0, and 4.0) M-type hexaferrites were characterized by employing XRD (X-ray Diffractometer). It is confirmed that, all the samples are in nanocrystalline and single phase, no impurity has been detected within the XRD limit. The magnetic hysteresis (m-H) loops revealed the ferromagnetic nature of nanoparticles (NPs). The coercive field were increasing with the increasing Cr3+ content, but after the percolation limit it decreases. The magnetocrystalline anisotropy is increasing with the Cr3+ concentration in samples and high values of magnetocrystalline anisotropy revealed that all samples are hard magnetic materials. Magnetic hys...

Lead free Bi0.5Na0.5TiO3 (BNT) and polyvinylidene fluoride (PVDF) based nanocomposite for energy storage applications

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 (er ≈ 78) relative to pure PVDF (er ≈ 10) at 100u2005Hz. In addition to this, it exhibits relaxor type ferroelectric behavior with energy storage efficiency up to 77% for the volume fraction (ϕ) of 10.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 (er ≈ 78) relative to pure PVDF (er ≈ 10) at 100u2005Hz. In addition to this, it exhibits relaxor type ferroelectric behavior with energy storage efficiency up to 77% for the volume fraction (ϕ) ...

Role of lattice distortion on diffuse phase transition temperatures in Bi0.5Na0.5TiO3-BaTiO3 [BNBTO] solid solutions

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.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 so...

Role of grain and grain boundary on the electrical and thermal conductivity of Bi0.9Y0.1Fe0.9Mn0.1O3 ceramics

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.