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Title: 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

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 materialsmore » remain insulating.« less
Authors:
 [1] ;  [2] ;  [1] ;  [2] ;  [1]
  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)
Publication Date:
OSTI Identifier:
22348597
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 51; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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