New data on the phase formation in the system NaF-KF-AlF3

The results of the studies of the composition and structure of the crystalline phase, which realized in the system NaF-KF-AlF3, have been presented. The thermal analysis data allowed conclude that the new phase was a polymorph of K2NaAl3F12. The crystal structure has been established by X-ray powder diffraction analysis. The lattice parameters are a=11,878(6)1 Å, с=6,9718(1) Å, c= 11,2493(5) Å, V=935.75 Å 3 S.G. Pcmn. The thermal phase decomposition on air have been studied by the high-temperature X-ray diffraction method.