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Issue 36, 2018
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Oriented nucleation and crystal growth of Ge-fresnoite (Ba2TiGe2O8) in 2BaO·TiO2·2GeO2 glasses with additional GeO2

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Abstract

Glasses of the mol composition 2BaO·TiO2·2GeO2 + xGeO2 (with x = 0.0, 0.2, 0.75 and 1.5 mol) were prepared, polished and crystallised at 730 and 970 °C for 5 h. All glasses showed the surface crystallisation of Ge-fresnoite (Ba2TiGe2O8) as well as the formation of BaGe4O9 at 970 °C. An additional unidentified phase occurs at the surfaces of the glass-ceramics with x = 0.0 and x = 0.2. The crystal orientations at the immediate surfaces were analysed by electron backscatter diffraction (EBSD) and showed that all glasses show a non-random orientation distribution, i.e. oriented nucleation at the surface. The intensity of the orientation preference increases with an increased amount of additional GeO2 and crystallising at higher temperatures leads to more discrete orientation preferences. BaGe4O9 shows the same oriented nucleation as Ge-fresnoite. The crystal growth into the bulk was analysed by EBSD and generally shows a growth selection towards the 001-texture previously associated with dendritic growth in this system. Crystallising the stoichiometric glass at 730 °C, however, led to the formation of a 110-texture during growth into the bulk. All analysed glasses show bulk nucleation except for the glass with 1.5 mol additional GeO2 where the opposing growth fronts collided in the middle of the ca. 1 mm thick sample. The effects of adding network formers to stoichiometric Ba-, Sr- and Ge-fresnoite glass-ceramics are compared and discussed.

Graphical abstract: Oriented nucleation and crystal growth of Ge-fresnoite (Ba2TiGe2O8) in 2BaO·TiO2·2GeO2 glasses with additional GeO2

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Publication details

The article was received on 09 Jul 2018, accepted on 22 Aug 2018 and first published on 29 Aug 2018


Article type: Paper
DOI: 10.1039/C8CE01123K
Citation: CrystEngComm, 2018,20, 5409-5421
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    Oriented nucleation and crystal growth of Ge-fresnoite (Ba2TiGe2O8) in 2BaO·TiO2·2GeO2 glasses with additional GeO2

    W. Wisniewski, J. Dimitrijevic and C. Rüssel, CrystEngComm, 2018, 20, 5409
    DOI: 10.1039/C8CE01123K

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