Ag3Ni2O4—A new stage-2 intercalation compound of 2H–AgNiO2 and physical properties of 2H–AgNiO2 above ambient temperature

Ag3Ni2O4 was obtained as single crystals from a mixture of 2H–AgNiO2 and Ag2O in oxygen high-pressure autoclaves (P63/mmc (no. 194), image, image Å, image). It may be regarded as a stage-2 intercalation compound of the host 2H–AgNiO2 and is the first staging compound constituted of alternating subvalent image and Ag+ sheets, inserted between NiO2− slabs. From a structural point of view, Ag3Ni2O4 represents an intermediate between AgNiO2 and the recently reported Ag2NiO2. The electronic structures of 2H–AgNiO2 and Ag3Ni2O4 have been investigated based on DFT band structure calculations. The high-temperature characteristics of the starting material 2H–AgNiO2 were investigated. The inverse magnetic susceptibility, electrical resistivity and differential scanning calorimetry (DSC) show a phase transition in the temperature range of image.