A new polymorph of eucryptite (LiAlSiO4), ε-eucryptite, and thermal expansion of α- and ε-eucryptite at high pressure
-
Jianzhong Zhang
,
Aaron Celestian
Abstract
X-ray diffraction experiments have been carried out on b-eucryptite (LiAlSiO4) at pressures up to 2.5 GPa and temperatures up to 1073 K in a large-volume apparatus. With room-temperature compression, we observed a phase transition to a new polymorph between 0.83 and 1.12 GPa. This transition is reversible in character. The new phase, referred to here as e-eucryptite, can be indexed according to an orthorhombic unit cell with a = 10.217(4) Å, b = 8.487(4), Å, c = 5.751(3) Å, and V = 498.7(4) Å3 for XRD data at 2.2 GPa and 298 K. On heating at 2.2 GPa, e-eucryptite and beucryptite were metastable over the temperature interval 298-873 K; at higher temperatures they underwent an irreversible phase transition to a-eucryptite.
Both hexagonal α-eucryptite and ε-eucryptite show anisotropic thermal expansion. For α-eucryptite, we obtained αa = 6.71(±0.25) × 10-6 K-1, αc = 1.07(±0.05) × 10-5 K-1, and αv = 2.42(±0.1) x 10-5 K-1 at 1.94(2) GPa over the temperature range 298-1073 K. For ε-eucryptite at 2.32(8) GPa, we find larger thermal expansion in a smaller temperature range 298-773 K, with αa = 1.47(±0.15) × 10-5 K-1, αb = 6.65(±1.33) x 10-6 K-1, αc = 7.83(±0.88) × 10-6 K-1, and αv = 2.99(±0.15) × 10-5 K-1. In combination with a previous determination of thermal expansion at ambient pressure, the pressure effect on volume thermal expansion of a-eucryptite is determined to be -2.68 × 10-6 GPa-1 K-1, and the temperature derivative of the bulk modulus is estimated to be -0.015 GPa/K.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Titanium in biotite from metapelitic rocks: Temperature effects, crystal-chemical controls, and petrologic applications
- Local equilibrium in polymetamorphic gneiss and the titanium substitution in biotite
- The enthalpy of formation and internally consistent thermodynamic data of Mg-staurolite
- Coexisting andalusite, kyanite, and sillimanite: Sequential formation of three Al2SiO5 polymorphs during progressive metamorphism near the triple point, Sivrihisar, Turkey
- Co-existing aluminum silicates in quartz veins: A quantitative approach for determining andalusite-sillimanite equilibrium in natural samples using oxygen isotopes
- Stability of corundum + quartz relative to kyanite and sillimanite at high temperature and pressure
- Andalusite-sillimanite replacement (Mazarrón, SE Spain): A microstructural and TEM study
- Hydroxyl-rich topaz in high-pressure and ultrahigh-pressure kyanite quartzites, with retrograde woodhouseite, from the Sulu terrane, eastern China
- Coesite exsolution from supersilicic titanite in UHP marble from the Kokchetav Massif, northern Kazakhstan
- Composition of synthetic tremolite-tschermakite solid solutions in amphibole + anorthiteand amphibole + zoisite-bearing assemblages
- Paragenesis and thermobarometry of Ca-amphiboles in the Barcroft granodioritic pluton, central White Mountains, eastern California
- B and Li in Proterozoic metapelites from the Black Hills, U.S.A.: Implications for the origin of leucogranitic magmas
- The role of Fe and cation order in the crystal chemistry of surinamite, (Mg,Fe2+)3(Al,Fe3+)3O[AlBeSi3O15]: A crystal structure, Mössbauer spectroscopic, and optical spectroscopic study
- Fe3+ and Fe2+ partitioning among silicates in metapelites: A synchrotron micro-XANES study
- Thermodynamic and structural behavior of analcime–leucite analogue systems
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- The crystal structures of grossular and spessartine between 100 and 600 K and the crystal chemistry of grossular-spessartine solid solutions
- The structures of becquerelite and Sr-exchanged becquerelite
- Elasticity and equation of state of orthoenstatite, MgSiO3
- Reidite: An impact-produced high-pressure polymorph of zircon found in marine sediments
- A new polymorph of eucryptite (LiAlSiO4), ε-eucryptite, and thermal expansion of α- and ε-eucryptite at high pressure
- Disordering during melting: An 17O NMR Study of crystalline and glassy CaTiSiO5 (titanite)
- Characterization of Mn oxides in cemented streambed crusts from Pinal Creek, Arizona, U.S.A., and in hot-spring deposits from Yuno-Taki Falls, Hokkaido, Japan
