Evidence for trivalent ytterbium in ytterbium-ammonia intercalation compounds of titanium disulfide

A prototypical ytterbium-ammonia intercalation compound of TiS2 having a nominal composition (Yb)0.060(NH3)0.32TiS2 has been synthesized by reaction of Yb-NH3 solutions with TiS2, characterized by thermogravimetric analysis and powder X-ray diffraction, and investigated by SQUID magnetometry and electron paramagnetic resonance. Both thermogravimetric and magnetic measurements confirm the presence of Yb3+. This compound is best described by the formula (Yb3+)0.060(NH4+)0.06(NH3)0.26TiS20.24-, and it crystallizes primarily in a 3R-type structure in which every layer is occupied by intercalated species. The intercalation process involves first the oxidation of Yb2+ to Yb3+, then the oxidation of NH3 to NH4+, and finally the insertion of neutral NH3. (Auth.)