Original paper

Transition metals in micas: synthesis and characterization of Co-rich Cs-tainiolite

Koch, Sebastian; Breu, Josef


Transition-metal rich micas offer interesting properties with regard to magnetism and electric conductivity and moreover allow for a post-synthesis modification of the layer charge by oxidation which makes them interesting for a variety of applications. In this line, a Co and F-rich Cs-mica analogue of tainiolite, Cs(Co2 2+Li)Si4O10F2, was synthesized by high-temperature melt synthesis. Subsequent annealing for 10 days yielded an almost pure, coarse-grained material. Single-crystal X-ray diffraction studies of the Cotainiolite showed the structure to be of the 1M polytype (C2/m(No.12) with cell parameters of a = 5.3051(11) Å, b = 9.1710(18) Å, c = 10.897(2) Å, β = 99.40(5)°, V = 523.05(18) Å 3. Characteristic geometric parameters were compared to the analogous Mn-rich and Fe-rich compounds. All three compounds are outside the compositional stability limits. Mn-rich Cs-tainiolite, as expected, possesses the smallest octahedral flattening angle, but this value then stays almost constant for Fe- and Co-rich tainiolite although the ionic radius steadily decreases going from Mn2+ over Fe2+, to the smallest Co2+. Rather, the individual octahedral distortions do not show the expected behaviour. Moreover, significant differences between the apical (1.607Å) and basal (1.658Å) bond lengths may be regarded as the main adjustments mechanism.


co-cs-tainiolite (synthetic)crystal structuremicasynthetic claystainiolite