Electrical transport mechanism in a newly synthesized rare earth double perovskite oxide Sr2CeTaO6

A rare earth double perovskite oxide strontium cerium tantalate, Sr2CeTaO6 (SCT) is synthesized by the solid state reaction technique for the first time. The determination of lattice parameters and the identification of phase are carried out by the Rietveld refinement method (RRM) using the Fullprof program in the space group P2(1)/n (C-2h(5)). A structure of SCT is obtained from RRM. The bond angle and bond length are calculated and listed in Table 1 for SCT. A small amount of impurity of CeO2 is found in the refinement with space group Fm3m. The scanning electron micrograph shows the average grain size similar to 2 mu m. The ac electrical property is investigated in the temperature range from 303 to 703 K and in the frequency range from 0.1 kHz to 1 MHz using impedance spectroscopy. The relaxation mechanism of SCT is explained in detail by fitting experimental impedance and electric modulus data with the modified Debye (Cole-Cole) model. The frequency-dependent electrical data are analyzed in the framework of the conductivity and modulus formalisms. The sigma(ac) data are fitted with Jonscher's universal power law. The dc conductivity (sigma(ac)) (calculated from sigma(ac)) follows an Arrhenius law with the estimated conduction activation energy =0.78 eV. The scaling behavior of imaginary part of electrical impedance (Z `') shows that the relaxation describes the same mechanism at various temperatures. (C) 2012 Elsevier B.V. all rights reserve

A Protease Isolated from the Latex of Plumeria rubra Linn (Apocynaceae) 1: Purification and Characterization

Purpose: To isolate, purify and characterize protease from the latex of the plant. Methods: Protease was isolated from the latex of Plumeria rubra Linn using acetone precipitation method and purified by a sequence of DEAE cellulose column chromatography, followed by two successive column purification in Sephadex G-50 and Sephadex G-200. The molecular weight of the purified protease was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDSPAGE). The protease was given a trivial name, Plumerin-R. Results: Plumerin-R showed a single protein band on SDS-PAGE and molecular weight was approximately 81.85 kDa. It remained active over a broad range of temperature but had optimum activity at 55 °C and pH 7.0 when casein was used as substrate. Activation of the protease by a thiol-activating agent indicated the presence of sulfhydryl as an essential group for its activity. Conclusion: A protease from the latex of Plumeria rubra Linn was purified to homogeneity by a simple purification procedure and then characterized

Structural, vibrational and electrical properties of ordered double perovskite oxide BaLaMnSbO6

BaLaMnSbO6 (BLMS) has been successfully synthesized by solid-state reaction technique. In contrast to earlier reports, Rietveld refinement of powder X-ray diffraction (XRD) data of BLMS shows tetragonal structure having space group I4/m. The octahedral tilt about the direction of the c-axis is found to be 8.99 degrees and the superlattice line (011) indicates the presence of cation ordering. FT-IR and Raman analysis as well as group theoretical investigation confirm the ordered tetragonal structure of BLMS with I4/m space group. The anti-phase distortions appear to be sufficiently large as detected by infrared and Raman spectroscopies, which give rise to the degeneracy and breaking of the symmetries of the normal modes. Impedance spectroscopy is used to investigate the dielectric relaxation and ac electrical conductivity in the temperature range of 303-403 K and in the frequency range of 0.1 kHz-1 MHz. Experimental electric modulus data are fitted to the Cole-Cole model in order to analyse the dielectric relaxation in BLMS. The frequency dependence ac electrical conductivity data are fitted to Jonscher's universal power law at various temperatures. The dc conductivity follows Arrhenius law with activation energy (E-a) 0.51 eV suggesting the polaron hopping. The complex impedance plane plots of BLMS indicate the presence of both grain and grain boundary effects and are analyzed by the electrical equivalent circuit consisting of a resistance and capacitance. (C) 2013 Elsevier B.V. All rights reserved

Cationic ordering and dielectric relaxation in a new series of double perovskite BaNdCoXO6 (X = Nb, Sb and Ta)

Three new double perovskites oxides have been synthesized using solid state reaction technique. XRD, SEM, EDAX, FTIR and impedance spectroscopy are used to analyze the structural and electrical data for all three compounds. (C) 2015 Elsevier Ltd. All rights reserved

Micro-structure, optical properties and ac conductivity of rare earth double perovskite oxides: Sr2ErNbO6

A polycrystalline rare earth double perovskite oxide strontium erbium niobate, Sr2ErNbO6 (SEN) is synthesized by the solid state reaction technique. Rietveld analysis of X-ray diffraction pattern reveals that SEN has monoclinic phase with space group P2(1)/n. Fourier transform infrared spectrum shows two phonon modes of the sample due to the antisymmetric NbO6 stretching vibration. The compound shows significant frequency dispersion in its dielectric properties. The frequency dependent ac conductivity spectra follow the Jonscher's universal power law. The conductivity at 100 Hz varies from 1.38 x 10(-6) Sm-1 to 2.34 x 10(-4) Sm-1 with the increase of temperature from 303 K to 653 K respectively. The increase of conductivity can be explained from the Correlated barrier hopping (CBH) model. The relaxation mechanism of the sample in the framework of electric modulus formalism is modelled by Davidson-Cole equation. The activation energy of the sample, calculated from both conductivity and modulus spectra is found to be similar to 0.8 eV which indicates that the conduction mechanism for SEN is due to ion hopping. The scaling behavior of imaginary electric modulus suggests that the relaxation describes the same mechanism at various temperatures. (C) 2013 Elsevier B.V. All rights reserved

A Protease Isolated from the Latex of Plumeria rubra Linn (Apocynaceae) 2: Anti-inflammatory and Wound- Healing Activities

Purpose: The aim of this study was to investigate the anti-inflammatory and wound-healing activities of the protease isolated from the latex of Plumeria rubra Linn. Methods: The protease was isolated from the latex of the plant by acetone precipitation method and given a trivial name, Plumerin-R. The anti-inflammatory activity of the protease was based on its effects on carrageenan-induced paw oedema in rats. Its wound healing effect was investigated using an excision wound rat model. Results: Four hours after treatment, the reduction in carrageenan-induced rat paw oedema by 20, 40 and 80 mg/kg body weight of plumerin-R was 21.6, 33.8 and 48.8 %, respectively, while oedema reduction by indomethacin (10 mg/kg) was 58.0 %. Plumerin-R showed significant (p<0.05) wound closure and epithelialization time compared with control. Conclusion: This study demonstrates that the protease, Plumerin-R, has significant anti-inflammatory and wound-healing properties

Cationic ordering, relaxation dynamics and polaron hopping in a new double perovskite oxide: BaPrCoTaO6

The Rietveld refinement method is used to investigate the cationic ordering of a new double perovskite oxide BaPrCoTaO6 (BPCT) synthesized by the solid-state reaction technique. X-ray diffraction pattern of BPCT shows monoclinic phase P2(1)/n (C-2h(5)) at room temperature with ordering of the B-cations. The super-lattice reflections suggest the existence of simultaneous in-phase and out-of-phase tilting. Scanning electron micrograph shows an average grain size similar to 3 mu m. The Fourier transform infrared spectra suggest two phonon modes. Impedance spectroscopy is used to investigate the relaxation dynamics and hopping mechanism in the temperature range of 303-523 K and in the frequency range of 0.1 kHz-1 MHz. Experimental electric modulus and electrical impedance data are fitted to the Cole-Cole model. The electrical conductivity data are fitted to Jonscher's universal power law. The activation energy (E-a) calculated from the Arrhenius plots is found to be similar to 0.36 eV which shows polaron hopping in BPCT. Impedance data that have capacitive and resistive components is represented by Nyquist diagram. (C) 2014 Elsevier B.V. All rights reserved

Rietveld refinement and dielectric relaxation of a new rare earth based double perovskite oxide: BaPrCoNbO6

A new rare earth based double perovskite oxide barium praseodymium cobalt niobate, BaPrCoNbO6 (BPCN) is synthesized by solid-state reaction technique. Rietveld analysis of X-ray diffraction (XRD) data shows that the compound crystallizes in a perovskite like tetragonal structure which belongs to the 14/mmm space group with lattice parameters a=b=5.6828(9) A, c=8.063(2) A. Structural analysis reveals 1:1 ordered arrangement for the Co2+ and Nb5+ cations over the six-coordinate B-sites of BPCN. The superlattice line (1 0 1) at 2 theta=19.10 degrees arising from the alternate ordering of Co2+ and Nb5+ sites is observed in the XRD pattern which confirms the presence of cation ordering in BPCN. Fourier transform infrared spectrum shows two phonon modes of the sample due to the antisymmetric NbO6 stretching vibration. The relaxation dynamics of the conductive process in BPCN is investigated in the temperature range 303 to 503 K and in the frequency range 100 Hz to 1 MHz using impedance spectroscopy. The relaxation mechanism of the sample in the framework of electric modulus formalism is modeled by Davidson-Cole model (DCM). The values of a (distribution of relaxation time) for the DCM varies from 0.1 to 0.3 which suggests the asymmetric distribution of relaxation time for BPCN. The activation energy of the sample, calculated from both conductivity and modulus spectra, are found to be almost the same similar to 0.4 eV, which indicates that the conduction mechanism for BPCN is polaron hopping. The scaling behaviour of the imaginary part of electric modulus suggests that the relaxation follows the same mechanism at various temperatures. (C) 2013 Elsevier Inc. All rights reserved

Dielectric relaxation and anti-ferromagnetic coupling of BiEu03 and BiGd03

BiEuO3 (BE) and BiGdO3 (BG) are synthesized by the solid-state reaction technique. Rietveld refinement of the X-ray diffraction data shows that the samples are crystallized in cubic phase at room temperature having Fm3m symmetry with the lattice parameters of 5.4925(2) and 5.4712(2) A for BE and BG, respectively. Raman spectra of the samples are investigated to obtain the phonon modes of the samples. The dielectric properties of the samples are investigated in the frequency range from 42 Hz to 1.1 MHz and in the temperature range from 303 K to 673 K. An analysis of the real and imaginary parts of impedance is performed assuming a distribution of relaxation times as confirmed by the Cole-Cole plots. The frequency-dependent maxima in the loss tangent are found to obey an Arrhenius law with activation energy similar to 1 eV for both the samples. The frequency-dependent electrical data are also analyzed in the framework of conductivity formalism. Magnetization of the samples are measured under the field cooled (EC) and zero field cooled (ZFC) modes in the temperature range from 5 K to 300 K applying a magnetic Field of 500 Oe. The FC and ZFC susceptibilities show that BE is a Van Vleck paramagnetic material with antiferromagnetic coupling at low temperature whereas BG is an anti-ferromagnetic system. The results are substantiated by the M-11 loops of the materials taken at 5 K in the ZFC mode. (C) 2014 Elsevier B.V. All rights reserve

<span style="font-size:10.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-US">Electronic structure and elastic properties of ATiO₃ (A = Ba, Sr, Ca) perovskites: A first principles study</span>

102-109The elastic constants of perovskite oxides ATiO3 (A = Ba, Sr, Ca) in the cubic phase are calculated using the full-potential linearized augmented plane wave method within the density functional theory in its generalized gradient approximation. The modified Becke-Johnson potential (TB-mBJ) is applied for the electronic structure calculation. The calculated results are used to obtain the Young's modulus, shear modulus, Poisson’s ratio, isotropic shear modulus, longitudinal, transverse and average sound velocities, Zener anisotropy factor, Kleinman parameter and Debye temperature of the systems. The calculated results are compared with the available experimental data