On the crystal structure of tribarium gallate (Ba3Ga2O6)

Single crystals of tribarium gallate (Ba3Ga2O6) have been synthesized from a melt with composition 70 mol.% BaO and 30 mol.% Ga2O3 in the temperature range between 1200 degreesC and 1400 degreesC. The compound adopts space group Pa (3) over bar With a = 16.746(9) Angstrom and Z = 24 formula units per unit cell. The refinement of the atomic parameters resulted in a residual of RI = 0.040 (wR2 = 0.102) for 1157 observed reflections (I >2 sigma (1)). Ba3Ga2O6 belongs to the group of cyclo-gallates and is closely related to K4SrGe3O9. Main building element are isolated, highly puckered, twelve-membered rings build by [GaO4]-tetrahedra. Charge balance is achieved by incorporation of Ba ions in the voids between the rings. The coordination number of the alkaline earth atoms is six, eight and nine, respectively.