Synthesis and Neutron Diffraction Study of La5Si2BO13, an Analog of the Apatite Mineral

✍ Scribed by D. Mazza; M. Tribaudino; A. Delmastro; B. Lebech

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 187 KB
• Volume: 155
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8929

✦ Synopsis

The structure re5nement of an apatite homolog, La 5 Si 2 BO 13 , was performed from neutron powder di4raction spectra. The re5ned sample was synthesized from gel during an investigation of apatite-like compounds with the general formula La 9.33؉x Si 6؊3y B 3y O 26 (space group, P6 3 /m; Z ‫؍‬ 2) in an electric furnace at T ‫؍‬ 11003C for 3 h. Two spectra, collected at ‫؍‬ 1.558 and 2.439 A > at Ris0 National Laboratory (Denmark), were processed together for a Rietveld structure re5nement (wRp all ‫؍‬ 0.087, Rp all ‫؍‬ 0.067, 2 ‫؍‬ 2.2; a 0 ‫؍‬ 9.5587(2); c 0 ‫؍‬ 7.2173(2) A > ).

Comparison with other apatite-like structures shows lower distortion in the M1 polyhedron and unusually short bond length from La in the M2 site and O4 oxygen in the column site (2.303 A > ). These results can be explained in view of the presence of trivalent La and divalent O, respectively, in the M1, M2 sites and in the column anion site, whereas in apatites these sites are occupied by divalent and monovalent ions respectively. 2000 Academic Press