Synthesis and crystal structure of LiNbO3-type Mg3Al2Si3O12


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LiNbO3-type Mg2.98(2)Al1.99(2)Si3.02(2)O12 was synthesized by recovering a run product from 2000 K and 45 GPa to ambient conditions using a large volume press. Rietveld structural refinements were carried out using the one-dimensional synchrotron XRD pattern collected at ambient conditions. The unit-cell lattice parameters were determined to be a = 4.8194(3) Å, c = 12.6885(8) Å, V = 255.23(3) Å3 with Z = 6 (Hexagonal, R3c).

 

Fig. 1.

MF-XRD patterns of akimotoite (bottom) with the pyrope composition (py-Ak) synthesized at 27 GPa and 1170 K and LiNbO3-type phase (top) also with the pyrope composition (py-LN) obtained from recovering a sample from 2000 K and 45 GPa.


Takayuki Ishii, Ryosuke Sinmyo, Tetsuya Komabayashi, Tiziana Boffa Ballaran, Takaaki Kawazoe, Nobuyoshi Miyajima, Kei Hirose, Tomoo Katsura (2017) Synthesis and crystal structure of LiNbO3-type Mg3Al2Si3O12: A possible indicator of shock conditions of meteorites. American Mineralogist 102 (9): 1947-1952, 2017. doi.org/10.2138/am-2017-6027 (Accepted Manuscript)