AgScO2 Revisited: Synthesis, Crystal Structure Refinement and Properties of the Single-phase 3R Polymorph

Silver scandium oxide AgScO2 has been obtained from Ag2O and Sc2O3 by solid-state reaction at elevated temperature and under high oxygen pressure in stainless-steel autoclaves. AgScO2 was obtained in the 3R Delafossite-type structure, R3̄m, with a = 3.21092(2), c = 18.5398(1) Å and Z = 3, containing virtually no admixtures of the 2H polytype. The fully ordered structure was solved by high-resolution X-ray powder diffraction data, R(F2) = 0.0436, 30 parameters. AgScO2 decomposes at around 740 ◦C into Ag and Sc2O3 with the release of oxygen. The conductivity of AgScO2 increases gradually with temperature from 5.79 × 10−18 to 7.94 × 10−10 S cm−1, and is ionic in nature, the activation energy for ion conduction being 75 kJ mol−1 in the temperature range from 250 to 425 ◦C.