Structural, electronic and thermodynamic properties of britholites Ca{sub 10−x}La{sub x}(PO{sub 4}){sub 6−x}(SiO{sub 4}){sub x}F{sub 2} (0 ≤ x ≤ 6): Experiment and theory

Journal Article · Sat Mar 01 00:00:00 EST 2014 · Materials Research Bulletin

DOI:https://doi.org/10.1016/J.MATERRESBULL.2013.12.022· OSTI ID:22348597

Njema, H. ^[1]; Boughzala, K. ^[1]; Said, M. ^[2]; Bouzouita, K. ^[1]

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1. Laboratoire de Chimie Industrielle, Ecole Nationale d’Ingnieurs de Sfax, BP1173 Sfax (Tunisia)
2. Laboratoire de la matière condensée et nanosciences, Département de Physique, Faculté des Sciences de Monastir, 5019 Monastir (Tunisia)

Highlights: • The structural and electronic properties of apatites with the general formula Ca{sub 10−x}La{sub x}(PO{sub 4}){sub 6−x}(SiO{sub 4}){sub x}F{sub 2} (0 ≤ x ≤ 6) have been investigated by means of the density functional theory. • The calculated enthalpy of formation of the compounds increased with the substitution degree. • The decrease in stability is probably due to the disorder induced in the Ca/LaO{sub 6}F polyhedron, following the substitution. - Abstract: The apatite-type compounds Ca{sub 10−x}La{sub x}(PO{sub 4}){sub 6−x}(SiO{sub 4}){sub x}F{sub 2} with 0 ≤ x ≤ 6 were prepared using a high temperature solid state reaction and were characterized by X-ray diffraction. The crystal structure, chemical bonding, electronic structure and formation energy of all relaxed structures were analyzed by density functional theory (DFT). The calculated results show that the predicted geometry can well reproduce the structural parameters. The incorporation of La{sup 3+} into the fluorapatite (FA) structure induced especially at the level of the S(2) sites a certain disorder which is responsible for the weakening in the stability with x. Excellent agreement were obtained between the calculated and experimental results. Moreover, the band structure indicates that despite the reduction of the band gap with x content all materials remain insulating.

• OSTI ID: 22348597
• Journal Information: Materials Research Bulletin, Vol. 51; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
APATITES
CERAMICS
CHEMICAL BONDS
CRYSTAL STRUCTURE
DENSITY FUNCTIONAL METHOD
ELECTRONIC STRUCTURE
FORMATION HEAT
INORGANIC COMPOUNDS
LANTHANUM IONS
LANTHANUM OXIDES
PHOSPHATES
SILICATES
SILICON OXIDES
SOLIDS
SYNTHESIS
X-RAY DIFFRACTION