Study of synthetic fluoroapatites

The paper deals with studies of the effect of alkaline earth and rare earth elements on the structure formation and properties of fluosilicates of the composition M4TR6(SiO4)6.F2, in which M=Mg, Ca, Sr, Ba and TR=Nd, Y, Yb. As a result of the investigations it is possible to follow variations in physical and chemical properties as a function of the type of alkaline-earth and rare-earth element involved. After roasting the samples were investigated by methods of crystal-optics and X-ray-phase analysis. Infra-red absorption spectra were obtained. It is shown that the synthesized silicates have a structure similar to that of apatite. The conditions for the synthesis of fluorine-containing silicate-apatites were worked out. It was established that the optimum condition for synthesis is roasting under a low argon pressure at 1200-13500C. The duration of thermal treatment depends primarily on the cation characteristics. (N.K.)