Effect of the fluorinating agent type (NH₄F, NaF, KF) on the particle size and emission properties of SrF₂:Yb:Er luminophores

Single-phase powders of SrF2:Yb:Er solid solutions with different particle sizes were synthesized using different fluorinating agents, such as ammonium fluoride, sodium fluoride and potassium fluoride, under the same synthesis conditions by co-precipitation from the aqueous solution technique. The incorporation of K and Na into the crystal lattice of strontium fluoride was found to be about 1 and 4 mol%, respectively. The achieved values of potassium and sodium concentration were equal to their solubility limits in the crystal lattice of strontium fluoride. The particle size increased with rising alkali element content. The embedding of sodium and potassium led to a change in the up-conversion emission spectrum and manifested in a redistribution of the intensities of the red luminescence bands (F-4(9/2 )-> (4)I1(5/2) transition). The achieved quantum yield of up-conversion luminescence (6.80% at 300 W cm(-2)) for the powders synthesized using sodium fluoride as a fluorinating agent was comparable to the values for single crystals.