Aluminum in magnesium silicate perovskite: Synthesis and energetics of defect solid solutions

Alexandra Navrotsky; Mirko Schoenitz; Hiroshi Kojitani; Hongwu Xu; Jianzhong Zhang; Donald J. Weidner; Masaki Akaogi; Raymond Jeanloz

doi:10.1557/proc-718-d2.2

Aluminum in magnesium silicate perovskite: Synthesis and energetics of defect solid solutions

Alexandra Navrotsky, Mirko Schoenitz, Hiroshi Kojitani, Hongwu Xu, Jianzhong Zhang, Donald J. Weidner, Masaki Akaogi, Raymond Jeanloz

Research output: Contribution to journal › Conference article › peer-review

1 Scopus citations

Abstract

MgSiO₃ - rich perovskite is expected to dominate the Earth's lower mantle (pressures > 25 GPa), with iron and aluminum as significant substituents. The incorporation of trivalent ions, M³⁺, may occur by two competing mechanisms Mg_A + Si_B = M_A + M_B and Si_B = Al_B + 0.5 V_O. Phase synthesis studies show that both substitutions do occur, and the nonstoichiometric or defect substitution is prevalent along the MgSiO₃ - MgAlO_2.5 join. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO₃ (perovskite) + 0.05 Al₂O₃ (corundum) = Mg_0.95Al_0.10Si_0.95O₃ (perovskite), has an enthalpy of-0.8±2.2 k J/mol. The nonstoichiometric reaction, 0.90 MgSiO₃ (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al₂O₃ (corundum) - MgS_0.9A_0.1O_2.95 (perovskite) has a small positive enthalpy of 8.5±4.6 kJ/mol. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiowüstite, and may significantly affect the elasticity, rheology and water retention of silicate perovskite in the Earth.

Original language	English (US)
Pages (from-to)	103-108
Number of pages	6
Journal	Materials Research Society Symposium - Proceedings
Volume	718
DOIs	https://doi.org/10.1557/proc-718-d2.2
State	Published - 2002
Externally published	Yes
Event	Perovskite Materials - San Francisco, CA, United States Duration: Apr 1 2002 → Apr 5 2002

ASJC Scopus subject areas

General Materials Science
Condensed Matter Physics
Mechanics of Materials
Mechanical Engineering

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10.1557/proc-718-d2.2

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title = "Aluminum in magnesium silicate perovskite: Synthesis and energetics of defect solid solutions",

abstract = "MgSiO3 - rich perovskite is expected to dominate the Earth's lower mantle (pressures > 25 GPa), with iron and aluminum as significant substituents. The incorporation of trivalent ions, M3+, may occur by two competing mechanisms MgA + SiB = MA + MB and SiB = AlB + 0.5 VO. Phase synthesis studies show that both substitutions do occur, and the nonstoichiometric or defect substitution is prevalent along the MgSiO3 - MgAlO2.5 join. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO3 (perovskite) + 0.05 Al2O3 (corundum) = Mg0.95Al0.10Si0.95O3 (perovskite), has an enthalpy of-0.8±2.2 k J/mol. The nonstoichiometric reaction, 0.90 MgSiO3 (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al2O3 (corundum) - MgS0.9A0.1O2.95 (perovskite) has a small positive enthalpy of 8.5±4.6 kJ/mol. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiow{\"u}stite, and may significantly affect the elasticity, rheology and water retention of silicate perovskite in the Earth.",

author = "Alexandra Navrotsky and Mirko Schoenitz and Hiroshi Kojitani and Hongwu Xu and Jianzhong Zhang and Weidner, {Donald J.} and Masaki Akaogi and Raymond Jeanloz",

year = "2002",

doi = "10.1557/proc-718-d2.2",

language = "English (US)",

volume = "718",

pages = "103--108",

journal = "Materials Research Society Symposium - Proceedings",

issn = "0272-9172",

publisher = "Materials Research Society",

}

TY - JOUR

T1 - Aluminum in magnesium silicate perovskite

T2 - Perovskite Materials

AU - Navrotsky, Alexandra

AU - Schoenitz, Mirko

AU - Kojitani, Hiroshi

AU - Xu, Hongwu

AU - Zhang, Jianzhong

AU - Weidner, Donald J.

AU - Akaogi, Masaki

AU - Jeanloz, Raymond

PY - 2002

Y1 - 2002

N2 - MgSiO3 - rich perovskite is expected to dominate the Earth's lower mantle (pressures > 25 GPa), with iron and aluminum as significant substituents. The incorporation of trivalent ions, M3+, may occur by two competing mechanisms MgA + SiB = MA + MB and SiB = AlB + 0.5 VO. Phase synthesis studies show that both substitutions do occur, and the nonstoichiometric or defect substitution is prevalent along the MgSiO3 - MgAlO2.5 join. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO3 (perovskite) + 0.05 Al2O3 (corundum) = Mg0.95Al0.10Si0.95O3 (perovskite), has an enthalpy of-0.8±2.2 k J/mol. The nonstoichiometric reaction, 0.90 MgSiO3 (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al2O3 (corundum) - MgS0.9A0.1O2.95 (perovskite) has a small positive enthalpy of 8.5±4.6 kJ/mol. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiowüstite, and may significantly affect the elasticity, rheology and water retention of silicate perovskite in the Earth.

AB - MgSiO3 - rich perovskite is expected to dominate the Earth's lower mantle (pressures > 25 GPa), with iron and aluminum as significant substituents. The incorporation of trivalent ions, M3+, may occur by two competing mechanisms MgA + SiB = MA + MB and SiB = AlB + 0.5 VO. Phase synthesis studies show that both substitutions do occur, and the nonstoichiometric or defect substitution is prevalent along the MgSiO3 - MgAlO2.5 join. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO3 (perovskite) + 0.05 Al2O3 (corundum) = Mg0.95Al0.10Si0.95O3 (perovskite), has an enthalpy of-0.8±2.2 k J/mol. The nonstoichiometric reaction, 0.90 MgSiO3 (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al2O3 (corundum) - MgS0.9A0.1O2.95 (perovskite) has a small positive enthalpy of 8.5±4.6 kJ/mol. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiowüstite, and may significantly affect the elasticity, rheology and water retention of silicate perovskite in the Earth.

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DO - 10.1557/proc-718-d2.2

M3 - Conference article

AN - SCOPUS:0036450472

SN - 0272-9172

VL - 718

SP - 103

EP - 108

JO - Materials Research Society Symposium - Proceedings

JF - Materials Research Society Symposium - Proceedings

Y2 - 1 April 2002 through 5 April 2002

ER -

Aluminum in magnesium silicate perovskite: Synthesis and energetics of defect solid solutions

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