Preparation, Structure Determination, and Redox Characteristics of New Calcium Copper Phosphates

The intercalation and deintercalation processes for nearly stoichiometric 1T-TaS2 have been investigated by X-ray powder diffraction, thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry. The maximum ammonia stoichiometry that has been prepared for a 4-month reaction time is (NH+4)0.06 (NH3)0.07 (1T-TaS2)0.06-. The reaction mechanism can be accounted for within a redox-rearrangement model in which part of the NH3 is oxidized to NH+4 upon intercalation, with the NH+4 decomposing at the host-layer edges to liberate NH3 and H2 upon deintercalation. All intercalation compounds prepared could be deintercalated at relatively low temperatures. The intercalates retained some 1TTaS2 host material, which may be associated with the rather low concentration of intercalant combined with intercalation reaction fronts that only partially penetrate the host in a nucleation and growth process. This study indicates that ammoniated 1T-TaS2 is a unique redoxrearrangement intercalation system.