New Sr sub(1-x-z)R sub(x)(NH sub(4)) sub(z )F sub(2+x-z) (R = Yb, Er) solid solution as precursor for high efficiency up-conversion luminophor and optical ceramics on the base of strontium fluoride

In this paper, we describe the use of self-fluorinating conditions for the thermal treatment of Sr sub(1-x-y-z)Yb sub(x)Er sub(y)(NH sub(4)) sub(z)F sub(2+x+y-z) precursor for the preparation of high-efficiency SrF sub(2):Yb:Er up-converter powders. We report actual SrF sub(2):Yb:Er compositions with up-conversion efficiencies exceeding 4% (pumping power 1 W/cm super(2) at 974 nm wavelength) and describe the synthesis of ceramics with higher than 80% transmittance at 0.42-7.0 mu m. The latter ceramics can be used as a potential IR radiation visualizer. For the first time, we present an analysis of correlation between up-conversion luminescence energy yield and specimen composition for SrF sub(2):Yb:Er nanopowders. Taking into account the observed erbium ion up-conversion luminescence in the red part of the visible spectrum, we recommend certain SrF sub(2):Yb:Er compositions for practical application in photodynamic cancer therapy.