Structural investigation of La{sub 9.33}Si{sub 6}O{sub 26}- and La{sub 9}AESi{sub 6}O{sub 26+{delta}}-doped apatites-type lanthanum silicate (AE=Ba, Sr and Ca) by neutron powder diffraction
- CEA Le Ripault, BP 16 37260 MONTS (France)
- LLB CEA Saclay, 91191 GIF sur YVETTE (France)
Crystalline structures of La{sub 9.33}Si{sub 6}O{sub 26} and La{sub 9}AESi{sub 6}O{sub 26+{delta}} (AE=Ba, Sr and Ca) doped apatites-type lanthanum silicates were investigated by X-ray and neutron powder diffraction at room temperature. The results obtained after different models testing show that the apatite structure is best described using the P6{sub 3} space group. The loss of the mirror symmetry perpendicular to the ionic conduction channel direction results from heterogeneous La{sup 3+}/AE{sup 2+} distribution of the sites so-called ''4f''. The Rietveld refinements do not show splitting of the conduction oxygen (0,0,14) site but rather a very large spread of the nuclear density associated to this site. This effect is more pronounced for the La{sub 9}AESi{sub 6}O{sub 26+{delta}}-doped compounds. Large anisotropic thermal displacement parameters are also observed for the oxygens associated to the isolated [SiO{sub 4}], suggesting a rotation of this tetrahedron around the Si site. Lastly, vacancies were also systematically observed in the lanthanum nine-coordinated sites.
- OSTI ID:
- 20905415
- Journal Information:
- Journal of Solid State Chemistry, Vol. 179, Issue 8; Other Information: DOI: 10.1016/j.jssc.2006.04.056; PII: S0022-4596(06)00229-5; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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