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Electron density distribution and crystal structure of Ca1-x/2AlSi(N3-xOx):Eu2+ (x ∼ 0.11)

Published online by Cambridge University Press:  06 March 2012

Daisuke Urushihara ,
Toru Asaka ,
Takashi Takeda ,
Naoto Hirosaki  and
Koichiro Fukuda
Daisuke Urushihara
Affiliation:
Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
Toru Asaka
Affiliation:
Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
Takashi Takeda
Affiliation:
Nano Ceramics Center, National Institute for Materials Science (NIMS), Ibaraki 305-0044, Japan
Naoto Hirosaki
Affiliation:
Nano Ceramics Center, National Institute for Materials Science (NIMS), Ibaraki 305-0044, Japan
Koichiro Fukuda*
Affiliation:
Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
*
a)Author to whom correspondence should be addressed. Electronic mail: fukuda.koichiro@nitech.ac.jp
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Abstract

Crystal structure of Ca1-x/2AlSi(N3-xOx):Eu2+ (x ∼ 0.11) has been characterized using an X-ray powder diffractometer and a transmission electron microscope equipped with an energy dispersive X-ray analyzer (EDX) and an electron energy loss spectrometer (EELS). The title compound is orthorhombic with space group Cmc21, Z = 4, unit-cell dimensions a = 0.979780(7) nm, b = 0.565197(4) nm, c = 0.506356(3) nm, and V = 0.280404(3) nm3. The atom ratio Al:Si was determined to be 1:1 by EDX, and the presence of O atoms in the crystal structure was confirmed by EELS. The x-value and the atomic coordinates of the final structural model were determined by the Rietveld method. The maximum-entropy methods-based pattern fitting (MPF) method was used to confirm the validity of the structural model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from MPF are Rwp = 9.18%, S = 1.17, Rp = 6.77%, RB = 1.91%, and RF = 0.86%. Atomic arrangements of the final structural model are in an excellent agreement with the three dimensional electron-density distributions determined by MPF.

Keywords

calcium aluminum silicon oxynitrideX-ray powder diffractionRietveld methodmaximum-entropy methodelectron density distributions
Type
Technical Articles
Information
Powder Diffraction , Volume 26 , Supplement S1 , December 2011 , pp. S38 - S43
Copyright
Copyright © Cambridge University Press 2011

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