X-ray luminescence of SrF$_2$:Eu nanopowders

Concentration series of single-phase SrF$_2$:Eu solid solutions with a particle size of $\approx$ 50 nm were synthesized by precipitation from aqueous solutions. The bands of europium in the di- and trivalent states as well as a band of intrinsic exciton luminescence of strontium fluoride were identified in the X-ray luminescence spectra. The most intense luminescence band is the band of trivalent europium with a maximum at 585–590 nm which corresponding to the $^5D_0\to{}^7F_1$ transition. The highest X-ray luminescence intensities upon excitation by an X-ray tube with silver and tungsten anodes are achieved for compositions containing about 15.0 mol.% and 7.5 mol.% europium, respectively.