The Suboxometallates A 9 MO 4 (A = Rb, Cs; M = Al, Ga, In, Fe, Sc)

Single crystals of the suboxometallates A 9 MO 4 (A = Rb, Cs;M = Al, Ga, Fe, Sc) were prepared by reaction of stoichiometric mixtures of M 2 O 3 with alkali metals and their oxides A 2 O. They crystallize in the tetragonal Cs 9 InO 4 structure type (space group I 4/ mcm ) and contain ortho ‐oxometallate(III) anions in a metallic matrix. Cesium can be partially substituted by rubidium, as shown for phases of arbitrary compositions (Rb x Cs 1– x )Cs 8 GaO 4 ( x = 0.57) and (Rb x Cs 1– x )Cs 8 InO 4 ( x = 0.87). The substitution leads to statistical occupation of one crystallographic position. The same holds for substitutions of M, as in Cs 9 (Al x In 1– x )O 4 ( x = 0.51) and Cs 9 (Sc x In 1– x )O 4 ( x = 0.68).