High-temperature synthesis and single-crystal X-ray structure determination of Sr10Sm6Si30Al6O7N54 - a layered sialon with an ordered distribution ofSi, Al, O, and N

The novel oxonitridoaluminosilicate Sr10Sm6Si30Al6O7N54 has been obtained b y the reaction of the powdered metals Sr and Sm with Si(NH)(2), SrCO3 and A lN using a radiofrequency furnace at a maximum reaction temperature of 1600 degrees C. The crystal structure of Sr10Sm6Si30Al6O7N54 has been determine d by single-crystal X-ray crystallography (Fmm2, Z = 4, a = 1706.94(9), b = 3332.4(2), c = 995.36(5) pm, R-1 = 0.0706, wR(2) = 0.1273). This sialon re presents a new structure type which has not been previously observed for a sialon. In the solid a capped double layer structure of the two-dimensional sialon network is formed by corner sharing SiON3, SiN4, AlON3 and AlN4 tet rahedra. A crystallographic differentiation of Si/Al and O/N seems reasonab le on the basis of a careful evaluation of the single-crystal X-ray diffrac tion data combined with lattice energy calculations using the MAPLE concept . (C) 2000 Editions scientifiques et medicales Elsevier SAS. All rights res erved.