Rietveld Refinement

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Sanjay Sharma - One of the best experts on this subject based on the ideXlab platform.

  • Eu3+/Tb3+-codoped Y2O3 nanophosphors: Rietveld Refinement, bandgap and photoluminescence optimization
    Journal of Physics D: Applied Physics, 2012
    Co-Authors: Sudipta Som, Sanjay Sharma
    Abstract:

    In this work, Eu-doped, Tb-doped and Eu, Tb-codoped Y2O3 nanophosphors were synthesized by the combustion synthesis method. The prepared phosphors were characterized by x-ray diffraction (XRD), Rietveld Refinement and Fourier transform infrared (FTIR) spectroscopy. XRD studies and Rietveld Refinement confirmed the body-centred cubic structure of doped and codoped phosphors. FTIR studies also confirmed the formation of these compounds. Thermal analysis results indicated that there was no phase transition for all the phosphors in the studied temperature range. In the optical properties, diffuse reflectance (DR) and photoluminescence (PL) measurements were performed. DR spectra were used to determine the bandgap and it increased in the doped and codoped samples due to the crystallite size effect. A strong characteristic emission from Eu3+ and Tb3+ ions was identified and the influence of doping concentration and annealing temperature on PL properties was systematically studied. Transfer of energy was observed from Tb3+ to Eu3+ ions in the codoped phosphor at room temperature.

  • eu3 tb3 codoped y2o3 nanophosphors Rietveld Refinement bandgap and photoluminescence optimization
    Journal of Physics D, 2012
    Co-Authors: Sudipta Som, Sanjay Sharma
    Abstract:

    In this work, Eu-doped, Tb-doped and Eu, Tb-codoped Y2O3 nanophosphors were synthesized by the combustion synthesis method. The prepared phosphors were characterized by x-ray diffraction (XRD), Rietveld Refinement and Fourier transform infrared (FTIR) spectroscopy. XRD studies and Rietveld Refinement confirmed the body-centred cubic structure of doped and codoped phosphors. FTIR studies also confirmed the formation of these compounds. Thermal analysis results indicated that there was no phase transition for all the phosphors in the studied temperature range. In the optical properties, diffuse reflectance (DR) and photoluminescence (PL) measurements were performed. DR spectra were used to determine the bandgap and it increased in the doped and codoped samples due to the crystallite size effect. A strong characteristic emission from Eu3+ and Tb3+ ions was identified and the influence of doping concentration and annealing temperature on PL properties was systematically studied. Transfer of energy was observed from Tb3+ to Eu3+ ions in the codoped phosphor at room temperature.

M. Almeida - One of the best experts on this subject based on the ideXlab platform.

Terrence J Udovic - One of the best experts on this subject based on the ideXlab platform.

  • electronic structure and Rietveld Refinement parameters of ti doped sodium alanates
    Journal of Alloys and Compounds, 2004
    Co-Authors: Vidvuds Ozolins, E H Majzoub, Terrence J Udovic
    Abstract:

    Abstract The structure of Ti-doped sodium aluminum deuteride has been determined using Rietveld Refinement of X-ray and neutron powder diffraction data and compared to values for undoped NaAlD 4 and NaAlH 4 . The refined lattice parameters for the tetragonal NaAlD 4 structure are found to be a =5.010 A and c =11.323 A, while those of the monoclinic Na 3 AlD 6 structure are a =5.402 A, b =5.507 A, c =7.725 A, and β =89.491°. Results of ab initio calculations of the lattice parameters are within a few percent of the Rietveld-refined values. The generalized gradient approximation (GGA) is found to produce significantly better agreement with the experimental data than the local-density approximation (LDA), which is attributed to a very inhomogeneous distribution of electronic density in the alanates. The Rietveld Refinement, LDA, and GGA results for the Al–H bond length in NaAlD 4 are 1.626, 1.634, and 1.631 A, respectively. Refined values of the Al–H bond lengths in Na 3 AlD 6 , are in agreement within 2% of earlier work on undoped Na 3 AlD 6 [J. Alloy Comp. 299 (1–2) (2000) 101]. The calculated GGA formation energies for the decomposition reactions of NaAlD 4 and Na 3 AlD 6 are 33.5 and 49.9 kJ/mol of H 2 , respectively. The corresponding LDA values are significantly higher: 44.6 and 70.3 kJ/mol of H 2 . Comparison with the experimental enthalpy data suggests that the GGA results are in a very good agreement with the measured Δ H [Proceedings of the 1999 DOE Hydrogen Program Annual Peer Review, NREL/CP-570-26938; J. Alloy Comp. 302 (1–2) (2000) 36]. Detailed theoretical analyses of the electronic band structure, valence charge density distribution, and lattice bonding properties are given.

  • electronic structure and Rietveld Refinement parameters of ti doped sodium alanates
    Journal of Alloys and Compounds, 2004
    Co-Authors: Vidvuds Ozolins, E H Majzoub, Terrence J Udovic
    Abstract:

    Abstract The structure of Ti-doped sodium aluminum deuteride has been determined using Rietveld Refinement of X-ray and neutron powder diffraction data and compared to values for undoped NaAlD 4 and NaAlH 4 . The refined lattice parameters for the tetragonal NaAlD 4 structure are found to be a =5.010 A and c =11.323 A, while those of the monoclinic Na 3 AlD 6 structure are a =5.402 A, b =5.507 A, c =7.725 A, and β =89.491°. Results of ab initio calculations of the lattice parameters are within a few percent of the Rietveld-refined values. The generalized gradient approximation (GGA) is found to produce significantly better agreement with the experimental data than the local-density approximation (LDA), which is attributed to a very inhomogeneous distribution of electronic density in the alanates. The Rietveld Refinement, LDA, and GGA results for the Al–H bond length in NaAlD 4 are 1.626, 1.634, and 1.631 A, respectively. Refined values of the Al–H bond lengths in Na 3 AlD 6 , are in agreement within 2% of earlier work on undoped Na 3 AlD 6 [J. Alloy Comp. 299 (1–2) (2000) 101]. The calculated GGA formation energies for the decomposition reactions of NaAlD 4 and Na 3 AlD 6 are 33.5 and 49.9 kJ/mol of H 2 , respectively. The corresponding LDA values are significantly higher: 44.6 and 70.3 kJ/mol of H 2 . Comparison with the experimental enthalpy data suggests that the GGA results are in a very good agreement with the measured Δ H [Proceedings of the 1999 DOE Hydrogen Program Annual Peer Review, NREL/CP-570-26938; J. Alloy Comp. 302 (1–2) (2000) 36]. Detailed theoretical analyses of the electronic band structure, valence charge density distribution, and lattice bonding properties are given.

Sudipta Som - One of the best experts on this subject based on the ideXlab platform.

  • Eu3+/Tb3+-codoped Y2O3 nanophosphors: Rietveld Refinement, bandgap and photoluminescence optimization
    Journal of Physics D: Applied Physics, 2012
    Co-Authors: Sudipta Som, Sanjay Sharma
    Abstract:

    In this work, Eu-doped, Tb-doped and Eu, Tb-codoped Y2O3 nanophosphors were synthesized by the combustion synthesis method. The prepared phosphors were characterized by x-ray diffraction (XRD), Rietveld Refinement and Fourier transform infrared (FTIR) spectroscopy. XRD studies and Rietveld Refinement confirmed the body-centred cubic structure of doped and codoped phosphors. FTIR studies also confirmed the formation of these compounds. Thermal analysis results indicated that there was no phase transition for all the phosphors in the studied temperature range. In the optical properties, diffuse reflectance (DR) and photoluminescence (PL) measurements were performed. DR spectra were used to determine the bandgap and it increased in the doped and codoped samples due to the crystallite size effect. A strong characteristic emission from Eu3+ and Tb3+ ions was identified and the influence of doping concentration and annealing temperature on PL properties was systematically studied. Transfer of energy was observed from Tb3+ to Eu3+ ions in the codoped phosphor at room temperature.

  • eu3 tb3 codoped y2o3 nanophosphors Rietveld Refinement bandgap and photoluminescence optimization
    Journal of Physics D, 2012
    Co-Authors: Sudipta Som, Sanjay Sharma
    Abstract:

    In this work, Eu-doped, Tb-doped and Eu, Tb-codoped Y2O3 nanophosphors were synthesized by the combustion synthesis method. The prepared phosphors were characterized by x-ray diffraction (XRD), Rietveld Refinement and Fourier transform infrared (FTIR) spectroscopy. XRD studies and Rietveld Refinement confirmed the body-centred cubic structure of doped and codoped phosphors. FTIR studies also confirmed the formation of these compounds. Thermal analysis results indicated that there was no phase transition for all the phosphors in the studied temperature range. In the optical properties, diffuse reflectance (DR) and photoluminescence (PL) measurements were performed. DR spectra were used to determine the bandgap and it increased in the doped and codoped samples due to the crystallite size effect. A strong characteristic emission from Eu3+ and Tb3+ ions was identified and the influence of doping concentration and annealing temperature on PL properties was systematically studied. Transfer of energy was observed from Tb3+ to Eu3+ ions in the codoped phosphor at room temperature.

P.s. Salamakha - One of the best experts on this subject based on the ideXlab platform.

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