SILICATES AND GERMANATES WITH THE STRUCTURE OF SILICOCARNOTITE

A number of lanthanoid-containing compounds Ca(3)Ln(2)(XO(4))(3) with X = Si, Ge have been prepared, which have the silicocarnotite structur e. With the silicates, Ln ranges from Sm to Lu, with the germanates on ly from Sm to Tb. Ca3Y2(SiO4)3 crystallizes in this structure type, to o. In the case of Ln = La-Nd, mixtures ''Ca(3)Ln(2)(XO(4))(3)'' are fo rmed containing apatite phases. The germanates Ca(3)Ln(2)(CeO4)(3) wit h Ln = Dy-Lu; Y, Sc and Ca3Sc2(SiO4)(3), have the garnet structure, as already known. In addition, the lead compounds Pb3La2(SiO4)(3), Pb3Y2 (SiO4)(3) and Pb2Y3(SiO4)(3)O-0.5 have been synthesized. They have an apatite structure where the halogen positions are unoccupied or half-o ccupied.