Synthesis and thermal decomposition of tetragonal RbClO4 and volume of fluid O-2 from 2 to 9 GPa

Publication Type  Journal Article
Year of Publication  2001
Authors  Walker, D.; Hughes, G.; Cranswick, L. M. D.; Clark, S. M.; Buhre, S.
Journal Title  Geochemistry Geophysics Geosystems
Volume  2
Pages  art. no.-2001GC000154
Journal Date  Oct 11
ISBN Number  1525-2027
Accession Number  ISI:000171523400002
Key Words  oxygen volume; equation of state; rbclo4; thermal decomposition; rbcl; compression; composition of the core; experimental mineralogy and petrology; equations of state; high-pressure behavior; high-pressures; state; core; parameters; equation; halides

Orthorhombic (O) RbClO4 transforms to a new tetragonal (T) form at pressures above 20 kbar. Thermal decomposition proceeds through the reversible equilibrium reaction T RbClO4 = B2 RbCl+2O(2) at modestly increasing temperatures centered similar to 550 degreesC over the pressure range investigated from 20 to 90 kbar. Cell volumes for T RbClO4 and B2 RbCl were determined by high-pressure, high-temperature, in situ X-ray diffraction on station 16.4 of the Daresbury Synchrotron Radiation Source, from which the partial molar volume of O-2 along the decomposition curve was determined. This volume (similar to 10 cm(3)/mol) is in close agreement with volumes determined from studies of the thermal decomposition of KClO3 and KClO4 but is difficult to reconcile with fluid O-2 volumes determined using shock wave techniques. If these new O-2 partial molar volumes are relevant to molten iron solutions, then storage of substantial amounts of O-2 in the core becomes feasible.


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