Synthesis, structure and magnetic properties of Na9Co2O7, a new mixed-valent sodium cobaltate(II,III)
摘要
Na9Co2O7 was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursors (Co3O4, NaN3 and NaNO3) were heated in a special regime up to 450°C and annealed at this temperature for 100 h in specially designed silver containers. Single crystals have been grown by annealing a Na2O/Na9Co2O7 mixture (molar ratio 1:2) at 500°C for 2000 h in silver crucibles, which were sealed in glass ampoules under dried Ar. According to the X-ray analysis of the crystal structure (Pca21, Z=4, a=9.5477(6) Å, b=9.9040(6) Å, c=10.1919(7) Å, 4103 independent reflections, R1