Crystal structure refinement of synthetic osumilite-type phases BaMg₂Al₆Si₉O₃₀, SrMg₂Al₆Si₉O₃₀ and Mg₂Al₄Si₁₁O₃₀BaMg₂Al₆Si₉O₃₀, SrMg₂Al₆Si₉O₃₀ and Mg₂Al₄Si₁₁ O₃₀ BaMg₂Al₆Si₉O₃₀, SrMg₂Al₆Si₉O₃₀ and Mg₂Al₄Si₁₁ O₃₀BaMg₂Al₆Si₉O₃₀, SrMg₂Al₆Si₉O₃₀ and Mg₂Al₄Si₁₁ O₃₀

Autor(en)

W. Winter, T. Armbruster, Christian Leopold Lengauer

Abstrakt

Three synthetic osumilite-type double-ring silicates of technical interest as crystalline bases of glass-ceramic materials, with compositions BaMg₂Al₆Si₉O₃₀, SrMg₂Al₆Si₉O₃₀ and Mg₂Al₄Si₁₁O₃₀ (MAS), were synthesized by crystallization of glasses; their crystal structures were subsequently refined.

The structure of BaMg₂AI₆Si₉O₃₀ (P6/mcc, a = 10.129(2), c = 14.340(2) Å) was refined to Rw = 2.46 % for 1020 single-crystal reflections with MoKα X-radiation. The structures of SrMg₂AI₆Si₉O₃₀ (a = 10.1273(5),
c = 14.2274(8) Å) and Mg₂AI₄Si₁₁O₃₀ (a = 10.058(2),c = 14.336(3) Å) were refined in space group P6/mcc from CuKα X-ray powder data using multiphase Rietveld methods.
The C site between consecutive double-ring units is occupied by Ba²⁺ and Sr²⁺ in BaMg₂AI₆Si₉O₃₀ and SrMg₂Al₆Si₉O₃₀,respectively,while it is empty in MAS osumilite. This leads to increased C-O2 distances in MAS osumilite (3.18(1) Å) compared to 3.041(1) and 3.025(9) Å for the Ba- and Sr-bearing compounds, respectively. The longer C-O2 distance is compensated by a stronger distortion of the neighbouring Tl double-rings and T2 tetrahedra. In BaMg₂AI₆Si₉O₃₀ and SrMg₂Al₆Si₉O₃₀,Mg is constrained to the octahedral A site whereas in MAS
osumilite the A octahedron and the T2 tetrahedron have a mixed Mg, AI occupation.

Osumilite-type compounds with partial A1 in the six-membered double-rings show a different T1-O-T1 angular distortion compared to double-ring silicates with pure Si₁₂O₃₀ units. The reason for this difference is not primarily the A1 concentration on T1 but the higher ionic valences on A and T2 which become necessary for charge balance. -from Authors

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

TH Darmstadt, Universität Bern

Journal

European Journal of Mineralogy

Band

7

Seiten

277-286

Anzahl der Seiten

10

ISSN

0935-1221

Publikationsdatum

1995

Peer-reviewed

Ja

ÖFOS 2012

105116 Mineralogie, 105113 Kristallographie

ASJC Scopus Sachgebiete

Geochemistry and Petrology

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/crystal-structure-refinement-of-synthetic-osumilitetype-phases-bamg2al6si9o30-srmg2al6si9o30-and-mg2al4si11o30bamg2al6si9o30-srmg2al6si9o30-and-mg2al4si11-o30-bamg2al6si9o30-srmg2al6si9o30-and-mg2al4si11-o30bamg2al6si9o30-srmg2al6si9o30-and-mg2al4si11-o30(310396c8-01a8-4cb7-9768-fa8a53ba3ce8).html