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dc.contributor.authorComodi, Paola
dc.contributor.authorZanazzi, Pier Francesco
dc.contributor.authorWeiss, Zdeněk
dc.contributor.authorRieder, Milan
dc.contributor.authorDrábek, Milan
dc.identifier.citationAmerican Mineralogist. 1999, vol. 84, no. 3, p. 325–332.en
dc.publisherMineralogical Society of Americaen
dc.relation.ispartofseriesAmerican Mineralogisten
dc.title"Cs-tetra-ferri-annite:" High-pressure and high-temperature behavior of a potential nuclear waste disposal phaseen
dc.identifier.locationNení ve fondu ÚKen
dc.description.abstract-enStructure deformations induced by pressure and temperature in synthetic "Cs-tetra-ferriannite" 1M [Cs1.78(Fe21 5.93Fe31 0.07)(Si6.15 Fe31 1.80Al0.05)O20(OH)4], space group C2/m, were analyzed to investigate the capability of the mica structure to store the radiogenic isotopes 135Cs and 137Cs. ‘‘Cs-tetra-ferri-annite’’ is not a mineral name, but for the sake of brevity is used here to designate a synthetic analog of the mineral tetra-ferri-annite. The bulk modulus and its pressure derivative determined by fitting the unit-cell volumes between 0 and 47 kbar to a third-order Birch-Murnaghan equation of state are K0 5 257(8) kbar and K09 5 21(1), respectively. Between 23 8C and 582 8C, the a and b lattice parameters remain essentially unchanged, but the thermal expansion coefficient of the c axis is ac 5 3.12(9) 3 1025 8C21. High pressure (P) and high temperature (T) produce limited internal strain in the structure. The tetrahedral rotation angle, a, is very small and does not change significantly throughout the P and T range investigated. Above 450 8C in air, ‘‘Cs-tetraferri- annite’’ underwent an oxidation of octahedral iron in the M2cis site, balanced by the loss of H and shown by a decrease of the unit-cell volume. Independent isobaric data on thermal expansion and isothermal compressibility data define the ‘‘geometric’’ equation of state for ‘‘Cs-tetra-ferri-annite’’: V/V0 5 1 1 3.0(1) 1025 T 2 2.68(9) 1023 P 1 2.0(2) 3 1025 P2 where T is in degrees Celsius, P is in kilobars. The a/b ratio of about 12 bar/8C indicate that the cell volume of ‘‘Cs-tetra-ferri-annite’’ remains unchanged under geothermal gradients of ;23 8C/km. On the whole, the data confirm that the structure of ‘‘Cs-tetra-ferri-annite’’ may be a suitable candidate for the storage of large ions, such as Cs in the interlayer and should be considered as a potential Synroc component.en

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