STRUCTURE OF THE COMPOUNDS LA3ALGE5O16, LA3GAGE5O16 AND CE3GAGE5O16

Hydrothermal synthesis in the systems LaCl3 (CeCl3)-Al(OH)(3) (Ga2O3)- GeO2 yielded crystals of composition La3AlGe5O16, La3GaGe5O16 is and C e3GaGe5O16, respectively. The syntheses were carried out at temperatur es of 1023 K-1073 K under pressures of 1000 bar. The space group of th e three substances was determined as P (1) over bar with the pseudosym metry P2(1)/(c). All compounds are isostructural. The lattice paramete rs are a = 4.794(4)Angstrom, b = 8.102(8)Angstrom, c = 15.722(8)Angstr om, alpha = 90.42(3)degrees, beta = 94.46(2)degrees, gamma = 89.91(2)d egrees for La3AlGe5O16, a = 4.827(4)Angstrom, b = 8.090(4)Angstrom, c = 15.707(6)Angstrom, alpha = 90.76(5)degrees, beta = 94.01(7)degrees, gamma = 90.01(7)degrees for La3GaGe5O16 and a = 4.768(7)Angstrom, b = 8.088(5)Angstrom, c = 15.600(2)Angstrom, alpha = 90.55(4)degrees, beta = 94.46(4)degrees, gamma = 89.63(4)degrees for Ce3AlGe5O16. There are two formula units in the unit cell.