Cs-ferriannite as a possible host for waste cesium: crystal structure and synthesis
Mellini, Marcello; Weiss, Zdenek; Rieder, Milan; Drábek, Milan
European Journal of Mineralogy Volume 8 Number 6 (1997), p. 1265 - 1272
published: Jan 8, 1997
manuscript accepted: Jun 24, 1996
manuscript received: Mar 8, 1996
ArtNo. ESP147050806005, Price: 29.00 €
Abstract Cs-ferriannite, ideally CsFe2+3(Fe3+Si3)O10(OH)2, was synthesized as euhedral crystals, starting from an oxide mix, at 550°C and 0.1 GPa water pressure. Using 860 independent reflections, the crystal structure of its 1M poly type was refined in the C2/m space group with R equal to 5.5 %. All octahedral positions as well as 23 % tetrahedral positions are occupied by iron. Its octahedral sheet is geometrically homooctahedral with all octahedra the same in size. The tetrahedral and octahedral sheets are nearly undistorted. Cs-ferriannite is the 1M mica with the largest unit cell known to date: a = 5.487(1) Å, b = 9.506(2) Å, c = 10.826(6) Å, ß = 99.83(3)°, Z = 2. The mica appears to be a stable crystalline phase that may serve for fixation and storage of radioactive cesium isotopes in its interlayer.