Structure of crystalline CaAl_2Si_2O_8 precipitated in a CaO-Al_2O_3-SiO_2 glass-ceramic

摘要

Metastable CaAl2Si2O8 crystalline phase was obtained via heat treatment of CaO-Al2O3-SiO2 glass with metallic molybdenum particles as nucleating agents. Its crystal structure was determined by aberration-corrected scanning transmission electron microscopy (Cs-STEM), Raman spectroscopy, and X-ray diffraction (XRD). Although the hexagonal structure was observed by Cs-STEM and Raman spectroscopy, Rietveld analysis revealed that a triclinic structure with space group P1 provided the best description of the crystal structure. The most appropriate lattice parameters were a = 5 .1163(5) angstrom, b = 5.1155(5) angstrom, c = 15.0031(15) angstrom, alpha = 91.319(3)degrees, beta= 88.172(3)degrees, and gamma = 120.279(3)degrees. The c-axis layers composing the hexagonal plane were slightly distorted a few degrees from their arrangement in the hexagonal CaAl2Si2O8 crystal. (C) 2018 Published by Elsevier B.V.