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Crystal structure of low-cristobalite-type Al0.5Ga0.5PO4: A combined Rietveld refinement of neutron and X-ray diffraction data

Published online by Cambridge University Press:  01 March 2012

S. N. Achary ,
A. K. Tyagi ,
S. K. Kulshreshtha ,
O. D. Jayakumar ,
P. S. R. Krishna ,
A. B. Shinde  and
K. R. Chakraborty
S. N. Achary
Affiliation:
Applied Chemistry Division, Bhabha Atomic Research Centre, Mumbai (400 085), India
A. K. Tyagi
Affiliation:
Applied Chemistry Division, Bhabha Atomic Research Centre, Mumbai (400 085), India
S. K. Kulshreshtha
Affiliation:
Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Mumbai (400 085), India
O. D. Jayakumar
Affiliation:
Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Mumbai (400 085), India
P. S. R. Krishna
Affiliation:
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (400 085), India
A. B. Shinde
Affiliation:
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (400 085), India
K. R. Chakraborty
Affiliation:
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai (400 085), India
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Abstract

The low-cristobalite-type modification of Al0.5Ga0.5PO4 is prepared by annealing the amorphous precipitate of stoichiometric phosphate at 1300 °C. The phase purity of the sample is ascertained by powder X-ray diffraction. The crystal structure is refined by Rietveld refinements of the neutron and X-ray diffraction data of the polycrystalline powder. This compound crystallizes in an orthorhombic lattice with unit cell parameters, a=7.0295(8), b=7.0132(8), and c=6.9187(4) Å, V=341.08(6) Å3, Z=4 (Space group C 2221, No. 20). The crystal structure analysis reveals the random distribution of the Al3+ and Ga3+ having tetrahedral coordination with typical M–O (M=Al3+:Ga3+) bond lengths as 1.74 Å. Similarly, the P5+ have tetrahedral coordination with typical P–O bond lengths 1.52–1.54 Å. The Mo4 and PO4 tetraheda are linked by common corners forming a three-dimensional framework lattice. The details of the crystal structure are presented in this paper.

Keywords

phosphatecristobaliteRietveld refinementcrystal structureneutron diffractionX-ray diffraction
Type
Technical Articles
Information
Powder Diffraction , Volume 20 , Issue 3 , September 2005 , pp. 207 - 211
Copyright
Copyright © Cambridge University Press 2005

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