Whitlockite-Related Phosphates Sr9A(PO4)7 (A=Sc, Cr, Fe, Ga, and In): Structure Refinement of Sr9In(PO4)7 with Synchrotron X-Ray Powder Diffraction Data
| Autor: | Vladimir A. Morozov, Masato Okui, Artem P. Malakho, Fujio Izumi, Takuji Ikeda, Alexei A. Belik, Bogdan I. Lazoryak |
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| Rok vydání: | 2002 |
| Předmět: |
Chemistry
X-ray Infrared spectroscopy engineering.material Condensed Matter Physics Electronic Optical and Magnetic Materials Ion Inorganic Chemistry Thermogravimetry Crystallography Octahedron Materials Chemistry Ceramics and Composites Whitlockite engineering Physical and Theoretical Chemistry Powder diffraction Monoclinic crystal system |
| Zdroj: | Journal of Solid State Chemistry. 168:237-244 |
| ISSN: | 0022-4596 |
| DOI: | 10.1006/jssc.2002.9716 |
| Popis: | Five phosphates, Sr 9 A (PO 4 ) 7 ( A =Sc, Cr, Fe, Ga, and In), were synthesized by the solid state method at (1270 to 1420) K and characterized by X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, thermogravimetry, and second-harmonic generation (SHG). SHG showed Sr 9 A (PO 4 ) 7 to be centrosymmetric. Sr 9 In(PO 4 ) 7 is structurally related to β -Ca 3 (PO 4 ) 2 (space group R 3 c ; a=10.439A and c=37.375A; Z=21) and Sr 9+ x A ′ 1.5− x (PO 4 ) 7 ( A ′=Mn, Fe, Co, Ni, Cu, and Cd; space group R3m;a≈10.6A and c≈19.7A Z=3), having a new type of a monoclinic superstructure. Structure parameters of Sr 9 In(PO 4 ) 7 were refined by the Rietveld method from synchrotron X-ray diffraction data on the basis of space group I2/a to afford lattice parameters of a=18.0425(2) A, b=10.66307(4) A, c=18.3714(2) A;, and β=132.9263(5)° ( Z =4). The asymmetric unit of Sr 9 In(PO 4 ) 7 contains five Sr, one In, four P, and 14 O sites. Sr 2+ ions are coordinated to either eight or nine oxide ions. Sr 2+ ions at an Sr4 site are disordered over two positions near a center of symmetry. In 3+ ions occupy an octahedral site. O12 atoms belonging to P1O 4 tetrahedra are highly disordered because they are bonded to the Sr4 atoms. |
| Databáze: | OpenAIRE |
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