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Title: Thermochemistry of stuffed quartz-derivative phases along the join LiAlSiO{sub 4}-SiO{sub 2}

Abstract

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 previouslymore » 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.« less

Authors:
; ; ;  [1];  [2]
  1. Princeton Univ., NJ (United States)
  2. State Univ. of New York, Stony Brook, NY (United States)
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
697149
Resource Type:
Journal Article
Journal Name:
American Mineralogist
Additional Journal Information:
Journal Volume: 84; Journal Issue: 9; Other Information: PBD: Sep 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; LITHIUM OXIDES; ALUMINIUM OXIDES; SILICON OXIDES; QUARTZ; SOLUTION HEAT; CRYSTAL STRUCTURE; ORDER-DISORDER TRANSFORMATIONS; FORMATION HEAT

Citation Formats

Xu, H., Heaney, P.J., Navrotsky, A., Topor, L., and Liu, J. Thermochemistry of stuffed quartz-derivative phases along the join LiAlSiO{sub 4}-SiO{sub 2}. United States: N. p., 1999. Web. doi:10.2138/am-1999-0913.
Xu, H., Heaney, P.J., Navrotsky, A., Topor, L., & Liu, J. Thermochemistry of stuffed quartz-derivative phases along the join LiAlSiO{sub 4}-SiO{sub 2}. United States. doi:10.2138/am-1999-0913.
Xu, H., Heaney, P.J., Navrotsky, A., Topor, L., and Liu, J. Wed . "Thermochemistry of stuffed quartz-derivative phases along the join LiAlSiO{sub 4}-SiO{sub 2}". United States. doi:10.2138/am-1999-0913.
@article{osti_697149,
title = {Thermochemistry of stuffed quartz-derivative phases along the join LiAlSiO{sub 4}-SiO{sub 2}},
author = {Xu, H. and Heaney, P.J. and Navrotsky, A. and Topor, L. and Liu, J.},
abstractNote = {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.},
doi = {10.2138/am-1999-0913},
journal = {American Mineralogist},
number = 9,
volume = 84,
place = {United States},
year = {1999},
month = {9}
}