ИСТИНА

Samples of NaLuF4 were synthesized via thermal decomposition of lutecium trifluoroacetate hydrate and sodium trifluoroacetate with and without an addition of β-cyclodextrin. Heating was carried out in 5 different modes (2, 25, 170 hours at the temperature of 400°C, 2 hours at the temperature of 600°C and 2 hours at the temperature of 700°C). At the temperature of 400°C products contained low-temperature hexagonal phase with some impurities of cubic phase were obtained. However the increase of calcination time leads to formation monophase samples of low-temperature hexagonal phase both for samples prepared with and without an addition of β-cyclodextrin. At the temperature of 600°C pure high-temperature hexagonal phase was obtained. When the temperature rises up to 700°C products obtained contain cubic phase with small amount of low-temperature hexagonal phase. By calcination time increase products contained almost pure cubic phase of NaLuF4 were obtained. All these results are in agreement with the stability of different crystal modifications of NaLuF4 [1]. After analyzing the morphology of substances using SEM it was found that the addition of β-cyclodextrin influences on the shape of the particles of substances obtained. Samples prepared without β-cyclodextrin consist of particles with roundish shape. At the same time samples synthesized with an addition of β-cyclodextrin have particles with more angulate form. The increase of the calcination temperature from 400 to 700°C leads to decreasing the difference between samples prepared with and without addition of β-cyclodextrin (Fig. 1). At the same time the increasing time of calcination at temperature 400°C does not leads to significant changes in samples morphology (Fig. 2) although this leads to change of samples phase composition according XRD data.