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Review

Composition, Thermal Expansion and Phase Transitions in Framework Silicates: Revisitation and Review of Natural and Synthetic Analogues of Nepheline-, Feldspar- and Leucite-Mineral Groups

School of Earth and Environment Sciences (SEES), University of Manchester, Manchester M13 9PL, UK
Solids 2021, 2(1), 1-49; https://doi.org/10.3390/solids2010001
Received: 5 November 2020 / Revised: 9 December 2020 / Accepted: 15 December 2020 / Published: 5 January 2021
(This article belongs to the Special Issue Feature Papers of Solids 2021)
Framework silicates form about 70% of the Earth’s crust, mainly feldspars ~50–60% and quartz ~10–15%. Less-abundant feldspathoids include nepheline-, leucite-, and sodalite-group minerals, rich in structurally challenging properties. This review paper deals with anhydrous feldspar-, nepheline-, and leucite/pollucite groups, emphasising the importance of parallel studies on natural and synthetic samples. Four topics are covered. For decades, petrologists have analysed nephelines and recalculated their compositions as endmember molecules but, by not following rules of stuffed-tridymite crystal chemistry, have not estimated reliably the excess SiO2 present in solid solution. Some materials scientists make similar mistakes, and a new approach is described here. Synthesis studies of analogue feldspars, nephelines, and leucite/pollucites led to collaborative studies, mainly using laboratory and synchrotron X-ray powder diffraction methods at room and elevated temperatures, to study thermal expansion and displacive phase transitions. Such work was recently expanded to address the spontaneous strain relations. Topics covered here include work on nepheline/kalsilite analogues in the system SrAl2O4—BaAl2O4; thermal expansion of (K,Na)Al-, RbAl-, RbGa-, and SrAl-feldspars; and thermal expansion and phase transitions in analogue leucites KGaSi2O6 (tetragonal to cubic) and K2MgSi5O12 (monoclinic to orthorhombic). Results are reviewed in the context of research published in mineralogical and more-widely in physical sciences journals. View Full-Text
Keywords: framework silicates; stuffed-tridymite-nepheline compositions; (Sr,Ba)Al2O4-kalsilite analogues; feldspar thermal expansion; analogue leucite/pollucites; displacive phase transitions framework silicates; stuffed-tridymite-nepheline compositions; (Sr,Ba)Al2O4-kalsilite analogues; feldspar thermal expansion; analogue leucite/pollucites; displacive phase transitions
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MDPI and ACS Style

Henderson, C.M.B. Composition, Thermal Expansion and Phase Transitions in Framework Silicates: Revisitation and Review of Natural and Synthetic Analogues of Nepheline-, Feldspar- and Leucite-Mineral Groups. Solids 2021, 2, 1-49. https://doi.org/10.3390/solids2010001

AMA Style

Henderson CMB. Composition, Thermal Expansion and Phase Transitions in Framework Silicates: Revisitation and Review of Natural and Synthetic Analogues of Nepheline-, Feldspar- and Leucite-Mineral Groups. Solids. 2021; 2(1):1-49. https://doi.org/10.3390/solids2010001

Chicago/Turabian Style

Henderson, C. M.B. 2021. "Composition, Thermal Expansion and Phase Transitions in Framework Silicates: Revisitation and Review of Natural and Synthetic Analogues of Nepheline-, Feldspar- and Leucite-Mineral Groups" Solids 2, no. 1: 1-49. https://doi.org/10.3390/solids2010001

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