Skip to Main Content
Skip Nav Destination
GEOREF RECORD

High-pressure phase behavior and equations of state of ThO (sub 2) polymorphs

Bethany A. Chidester, Olivia S. Pardo, Rebecca A. Fischer, Elizabeth C. Thompson, Dion L. Heinz, Clemens Prescher, Vitali B. Prakapenka and Andrew J. Campbell
High-pressure phase behavior and equations of state of ThO (sub 2) polymorphs
American Mineralogist (May 2018) 103 (5): 749-756

Abstract

ThO (sub 2) is an important material for understanding the heat budget of Earth's mantle, as well as the stability of nuclear fuels at extreme conditions. We measured the in situ high-pressure, high-temperature phase behavior of ThO (sub 2) to approximately 60 GPa and approximately 2500 K. It undergoes a transition from the cubic fluorite-type structure (thorianite) to the orthorhombic alpha -PbCl (sub 2) cotunnite-type structure between 20 and 30 GPa at room temperature. Prior to the transition at room temperature, an increase in unit-cell volume is observed, which we interpret as anion sub-lattice disorder or pre-transformation "melting" (Boulfelfel et al. 2006). The thermal equation of state parameters for both thorianite [V0 = 26.379(7), K (sub 0) = 204(2), alpha K (sub T) = 0.0035(3)] and the high-pressure cotunnite-type phase [V (sub 0) = 24.75(6), K0 = 190(3), alpha K (sub T) = 0.0037(4)] are reported, holding K (sub 0) ' fixed at 4. The similarity of these parameters suggests that the two phases behave similarly within the deep Earth. The lattice parameter ratios for the cotunnite-type phase change significantly with pressure, suggesting a different structure is stable at higher pressure.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 103
Serial Issue: 5
Title: High-pressure phase behavior and equations of state of ThO (sub 2) polymorphs
Affiliation: University of Chicago, Department of the Geophysical Sciences, Chicago, IL, United States
Pages: 749-756
Published: 201805
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 50
Accession Number: 2018-052690
Categories: General geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2018

or Create an Account

Close Modal
Close Modal