Synthesis of KGd₂F₇:Yb:Er Luminophores by Co-Precipitation from Aqueous Solutions

Single-phase powders of a KGd1.52Yb0.40Er0.08F7 solid solution with an average particle size of 350 nm are synthesized by co-precipitation from aqueous solutions with a different order of mixing reagents. Surface leaching processes of potassium are revealed and studied. The optimal temperature of thermal treatment (525 degrees C) is determined. It enables the achievement of the energy yield of erbium up-conversion luminescence of 1.30 +/- 0.02% at the excitation wavelength of 974 nm with a pump power density of 1 W/cm(2).