Thermochemistry of stuffed quartz-derivative phases along the join LiAlSiO[sub 4]-SiO[sub 2]
- Princeton Univ., NJ (United States)
- State Univ. of New York, Stony Brook, NY (United States)
Enthalpies of drop-solution ([Delta]H[sub drop-soln]) of a suite of stuffed quartz-derivative phases with the composition Li[sub 1[minus]x]Al[sub 1[minus]x]Si[sub 1+x]O[sub 4] (0 [le] x [le] 1) have been measured in molten 2PbO[center dot]B[sub 2]O[sub 3] at 974 K. Substitution of Si[sup 4+] for Li[sup +] + Al[sup 3+] results in more exothermic enthalpies of drop-solution, which is consistent with behavior seen in other crystalline and glassy aluminosilicates. Al/Si ordering serves to stabilize these phases, and long-range ordering for compositions with x approximately <0.3 can be discerned in both calorimetric data and in structural data obtained by electron and synchrotron X-ray diffraction (XRD). In contrast, a structural but not an energetic discontinuity is apparent at x [approx equal] 0.65, which corresponds to a compositionally induced [alpha]-[beta] quartz transition with a small enthalpy of transformation. An enthalpy for the Al/Si order-disorder reaction in [beta]-eucryptite was measured as 25.9 [+-] 2.6 kJ/mol. Standard molar enthalpies of formation of the stuffed quartz-derivative phases from constituent oxides ([Delta]H[sub f.ox][sup 0]) and elements ([Delta]H[sub f.el][sup 0]) at 298 K also are presented. [Delta]H[sub f.ox][sup 0] = [minus]69.78 [+-] 1.38 kJ/mol and [Delta]H[sub f.el][sup 0] = [minus]2117.84 [+-] 2.50 kJ/mol for [beta]-eucryptite, which are in good agreement with results previously determined by HF solution calorimetry at 346.7 K (Barany and Adami 1966). The enthalpies of formation of other compositions are reported for the first time.
- OSTI ID:
- 6063909
- Journal Information:
- American Mineralogist, Vol. 84:9; ISSN 0003-004X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM OXIDES
CRYSTAL STRUCTURE
FORMATION HEAT
LITHIUM OXIDES
ORDER-DISORDER TRANSFORMATIONS
QUARTZ
SILICON OXIDES
SOLUTION HEAT
ALKALI METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
ENTHALPY
LITHIUM COMPOUNDS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
REACTION HEAT
SILICON COMPOUNDS
THERMODYNAMIC PROPERTIES
360606* - Other Materials- Physical Properties- (1992-)
360602 - Other Materials- Structure & Phase Studies