Some Aspects of the Intercalation Chemistry of the Niobium and Tantalum Carbide Chalcogenides Nb2S2S, Ta2S2C and Ta2Se2C

Abstract

It is shown that metastable 1T-Nb2S2C can act as a host lattice for intercalation by soft chemical methods similar to isotypic Ta2S2C. The hydrated intercalation compounds Mx(H2O) y[Nb2S2C] (M…Na, K) are prepared by ion exchange in Cux[Nb2S2C] using NaCN or KCN or by reductive intercalation into the host lattices T2S2C at pH~10 using dithionite as reducing agent. The intercalation phases are characterized by TGA and X-ray powder diffraction. Nax(H2O)y[Nb2S2C] and Nax(H2O)y[Ta2S2C] have an expanded 1T-type with two layers of co-intercalated water while in Kx(H2O)y[Nb2S2C] only one layer of water is held by the less hydrated potassium ions. Kx(H2O)y[Nb2S2C] has a 3R(Ib)-type stacking. The intercalation phases are not very stable, especially Nax(H2O)y[Nb2S2C] and Nax(H2O)y[Ta2S2C] are very quickly deintercalated by oxidation. After deintercalation colloidal suspensions are formed. Ethylene diamine is spontaneously intercalated into Nb2S2C and Ta2S2C. Nb2S2C.enx has a 3R(Ib)-type stacking similar to that of Kx(H2O)y[Nb2S2C]. Ta2Se2C is isotypic to 1T- Ta2S2C (P m1, a = 3.313(1) Å, c = 8.968(2)Å, Z = 1). Ta2Se2C does not form intercalation phases under soft chemical conditions.