Sun Yat Sen Univ, Sch Chem & Chem Engn, State Key Lab Optoelect Mat & Technol, Guangzhou 510275, Guangdong, Peoples R China
; Chinese Acad Sci, Changchun Inst Appl Chem, Lab Rare Earth Chem & Phys, Changchun 130022, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Lab Beijing Synchrotron Radiat, Beijing 100039, Peoples R China
The coordination numbers for the samarium atoms and the Sm-O bond distances in SrB4O7:Sm and SrB6O10:Sm prepared in air were determined by means of Sm-L-3 edge EXAFS. The coordination. was found to be nine-folded for both these hosts and the bond distance was 2.40-2.42 Angstrom in SrB4O7:Sm and 2.42-2.44 Angstrom in SrB6O10:Sm. For SrB4O7:Sm the coordination number is coincident with that of the strontium. atoms suggesting the substitution of the samarium atoms at the strontium sites. The coordination number of the strontium atoms in SrB6O10 was also suggested to be nine assuming the same type of substitution. The valences of samarium were determined from the luminescent spectra. Both divalent and trivalent ions were present in both SrB4O7:Sm and SrB6O10:Sm, while the fraction of Sm2+ was higher in the former than in the latter. This difference has been assigned to the difference in rigidity between the B-O networks in these structures. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.