Depleted brittle mica structure determination in Ba-phlogopite glass–ceramics
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This study concerns the bulk mica phase of a barium phlogopite glass–ceramic, with potential applications in Computer Aided Design and Computer Aided Manufacturing in dentistry, which has been studied in detail and characterized for the first time. A number of analytical techniques including powder X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, electron micro-probe analysis (EMPA), single crystal XRD and Monte-Carlo methods have been used to determine the mica phase composition and crystallographic structure. This has led to the identification of a new species of trioctahedral interlayer deficient brittle mica with an ideal formula of Ba2/3Mg3(Si8/3Al4/3)O10F2. Monte-Carlo simulations of Si/Al cation ordering indicate that the (Si8/3Al4/3) tetrahedral composition is unique and energetically favoured over that of the original assumed mica phase of Ba0.5Mg3(Si3AlO10)F2. The general mica composition X0.5Mg3(Si3Al)O10F2 where X is a divalent interlayer cation; therefore, does not precipitate in brittle mica glass–ceramics.
KeywordsRietveld Refinement Single Crystal Diffraction Single Crystal Growth Interlayer Cation General Mica
We are grateful to the Engineering and Physical Sciences Research Council (EPSRC) for financial support. Practical assistance was provided by Geoff Parr, University of Salford Analytical Services (UK), with XRD/SEM/EDS, Dr. Eric Condliffe, University of Leeds Institute for Materials Research (UK), with EMPA and Colin Kilner, University of Leeds (Chemistry), with the single crystal diffraction experiment.
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