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Study of Ga(3+)-Induced Hydrothermal Crystallization of an α-Quartz Type Ga(1-x)Fe(x)PO(4) Single Crystal by in Situ X-ray Absorption Spectroscopy (XAS).
MedLine Citation:
PMID:  23057790     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The dissolution of α-FePO(4) and the α-Ga(0.75)Fe(0.25)PO(4) solid solution with α-quartz-type structures under hydrothermal conditions in 1 M HNO(3) aqueous solution was investigated by in situ X-ray absorption spectroscopy (XAS) at the Fe K-edge. The solubility of α-FePO(4) increases with temperature and is higher at 25 MPa than at 50 MPa. The Fe(3+) cation in solution is 6-fold coordinated with an average Fe-O distance close to 2.0 Å. A similar experiment was performed with a solid solution of α-quartz-type Ga(0.75)Fe(0.25)PO(4) as the starting phase under a pressure of 25 MPa. By varying the temperature from 303 K up to 573 K a single crystal was grown with 23% Fe(3+) with the α-quartz-type structure. These results show that the crystallization of pure α-quartz-type FePO(4) by the hydrothermal method is not possible due to the formation of very stable Fe(3+) hexa-aquo complexes [Fe(H(2)O)(6)](3+) and to the absence of FeO(4) tetrahedra in solution. Ga(3+) cations in solution induce the formation of gallophosphate complexes at the solid-liquid interface, which are at the origin of the nuclei for crystallization. We propose a crystallization mechanism in which the Fe(3+) substitutes Ga(3+) with a 4-fold coordination in mixed (iron/gallo)-phosphate complexes that leads to the growth of an α-quartz-type Ga(0.77)Fe(0.23)PO(4) single crystal.
Authors:
Manhal Souleiman; Olivier Cambon; Abel Haidoux; Julien Haines; Claire Levelut; Vincent Ranieri; Jean-Louis Hazemann
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-11
Journal Detail:
Title:  Inorganic chemistry     Volume:  -     ISSN:  1520-510X     ISO Abbreviation:  Inorg Chem     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0366543     Medline TA:  Inorg Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Institut Charles Gerhardt Montpellier, Equipe C2M, UMR CNRS-UM2-ENSCM-UM1 5253, Université Montpellier 2 , Place Eugène Bataillon, CC1504, 34095 Montpellier Cedex 5, France.
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