Schnick, Wolfgang; Huppertz, Hubert; Lauterbach, Rainer
High temperature syntheses of novel nitrido- and oxonitrido-silicates and sialons using rf furnaces.
In: Journal of materials chemistry, Vol. 9, Nr. 1: S. 289-296
The high-temperature reaction of pure metals with silicon diimide Si(NH)2 in a specially developed radiofrequency furnace has been successfully applied to the synthesis of novel highly condensed nitridosilicates. With SrCO3 as an additional starting material this procedure has now been extended to the synthesis of oxonitridosilicates and oxonitridoaluminosilicates (sialons). Two novel sialons SrSiAl2 O3 N2 [space group P21 21 21 (no. 19), a=491.89(6), b=789.73(7), c=1134.94(18) pm, Z=4] and SrErSiAl3 O3 N4 [space group P63 mc (no. 186), a=606.53(3), c=985.90(8) pm, Z=2] have been obtained as coarsely crystalline materials. According to single crystal X-ray diffraction both compounds adopt structure types which are unprecedented for sialons. They derive from the nitridosilicates LnSi3 N5 (Ln=La, Ce, Pr, Nd) and MYbSi4 N7 (M=Sr, Ba, Eu), respectively, by partial substitution of Si by Al and N by O. For SrSiAl2 O3 N2 and SrErSiAl3 O3 N4 an unambiguous crystallographic differentiation between the tetrahedral centres (Al and Si) as well as the bridging atoms of the framework structures (N and O) seems reasonable.