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- SourceAvailable from: Paruchuri Kondaiah[Show abstract] [Hide abstract]
ABSTRACT: Thin films of tungsten trioxide (WO3) have been prepared by RF reactive magnetron sputtering of tungsten target at different substrate temperatures in the range 303–673 K and at fixed oxygen partial pressure of 6×10−2 Pa and sputter pressure of 4 Pa. The effect of substrate temperature on the structural, morphological, optical and electrochromic properties of WO3 films was systematically studied. The films formed at 303 K were of X-ray amorphous, while those deposited at substrate temperatures ≥473 K were crystallized into orthorhombic phase WO3. The crystallite size of the films increased from 17 to 24 nm with increase of substrate temperature from 473 to 673 K. Raman studies confirmed that the presence of O–W–O and W=O bonds in WO3 films. The surface morphology of the films was significantly varied with substrate temperature. The optical transmittance data revealed that the optical band gap increased from 3.08 to 3.48 eV and refractive index increased from 2.18 to 2.26 with increase of substrate temperature from 303 to 673 K respectively. The WO3 films formed at substrate temperature of 473 K exhibited better optical transmittance modulation of 40% between colored and bleached state with a color efficiency of 33.8 cm2/C and diffusion coefficient of 1.85×10−11 cm2/s.Physica B Condensed Matter 12/2014; 454:141–147. DOI:10.1016/j.physb.2014.07.029
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ABSTRACT: Keeping in view of the recent increased interest towards phosphor materials and its applications, an attempt has been made in the present paper to analyze the new NaPbB5O9:Dy3+ phosphor with different Dy3+ concentrations. Special attention is paid to investigate their crystal structure, morphology and luminescence properties. X-ray diffraction (XRD) results confirm the formation of NaPbB5O9: Dy3+ phosphor powder. Functional groups present in the phosphors were examined by Fourier transform infrared (FTIR) spectroscopy. The scanning electron microscope (SEM) images show that the grains size is in micrometer range. Photoluminescence spectra were recorded with different excitation wavelengths for the investigated phosphor and analyzed the variation of intensity of emission bands with Dy3+ ion concentration. Color co-ordinates were calculated and are used to characterize the color of the phosphor. It is found that the emission color of Dy3+-doped NaPbB5O9 powders depends on the doping concentration of Dy3+ ion and excitation wavelength.Journal of Physics and Chemistry of Solids 11/2014; 75(11). DOI:10.1016/j.jpcs.2014.05.006
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ABSTRACT: LiFePO4 is one of the most promising cathode materials as it offers low cost, high abundance, appropriate theoretical capacity and environmental friendly. In the present investigation, nano-crystalline LiFePO4 has been synthesized by hydrothermal method and studied spectroscopic and microscopic properties. The XRD and TEM studies exhibited the formation of orthorhombic structure with Pnma space group. The X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy studies confirm the phase purity of the LiFePO4 powder. The electrochemical characteristics of LiFePO4 are measured in non-aqueous region. It exhibited a good reversible cyclic voltammogram on sweeping the potential upward and downward. The chronopotentiometric measurements performed at various C-rates and the cell exhibited a discharge capacity of 143 mA h/g at 0.1 C with good cycling stability.Journal of Alloys and Compounds 11/2014; 614:13–19. DOI:10.1016/j.jallcom.2014.06.072
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