ИСТИНА

In this work a new synthetic approach to obtaining metal fluorides MF2 (M = Ca, Sr, Ba) and fluorite-type solid solutions M1-xYbxF2+x (M=Ca, Sr, Ba) with beta-cyclodextrin is proposed. The synthesis was carried out by thermal decomposition of the metal trifluoroacetate hydrates with beta-cyclodextrin. This method has some important advantages: the simplicity of the process and low synthesis temperature. The preparation of simple metal fluorides MF2 (M = Mg, Ca, Sr, Ba) shows that the addition of beta-cyclodextrin into the reaction mixture leads to the formation of high dispersive metal fluorides [1] that have relatively large surface area (Fig. 1). This fact opens the opportunities to use these materials as catalysts or the supports for catalysts. Also it is interesting to mention that there is a specific content of beta-cyclodextrin in the reaction mixture and its value is various for different metal fluorides. The optimal conditions for obtaining pure samples for each metal fluoride with the large surface area are given in the study. Also it was shown that the use of beta-cyclodextrin is very effective for the preparation of fluorite-type solid solutions M1-xYbxF2+x (M = Ca, Sr, Ba) [2]. It should be emphasized that the decomposition of the metal trifluoroacetates hydrates without beta-cyclodextrin does not lead to the formation of these solid solutions. Moreover, the increase of the synthesis temperature or the synthesis time does not result in obtaining these substances if the reaction mixture does not contain beta-cyclodextrin. However, the using of beta-cyclodextrin allows to obtain pure fluorite-type solid solutions with homogeneous distribution of elements under mild temperature conditions.