Polyvalency in post transition metal intercalation compounds of 2H-TaS2: a TDPAC study
We report on the in situ measurement of the nuclear quadrupole interaction (NQI) of radioactive 181Ta labels in 2H-TaS2 during thermal intercalation of the post transition metals In, Ga, Sn and Cd. At sufficiently high temperatures all intercalates diffuse rapidly enough to yield a motionally averaged NQI. Based on a previously determined NQI-frequency versus charge transfer relationship we obtain for a formal uptake of x = 1 (intercalate/TaS2) a formal average valence state of <v> = + 1 for In and Ga and <v> ∿ + 2/3 for Cd and Sn, suggesting the formation of an intercalate conduction band in the latter two cases. During intercalation metastable intermediate phases with high charge transfer show up for Ga and Sn. Moreover, for InxTaS2 we observe a continuous decrease of <v> from +1.75 towards +1.0 when x increases from ∿ 0.33 towards ∿ 1.00. Both observations suggest the formation of higher oxidation states (Sn4+, In3+, Ga3+) at low intercalate concentrations.
KeywordsHigh Oxidation State Nuclear Quadrupole Inter Average Valence Time Differential Perturb Angular Correlation Partial Charge Transfer
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