HYDROTHERMAL GROWTH AND PROPERTIES OF KGDF4

The hydrothermal phase equilibria of the KF-GdF3-H2O system were studied at a temperature of 450 degrees C and 10 kpsi. Crystals of K2GdF5, KGdF4 and KGd2F7 were grown. The fluorides were found to be stable only with excess KF in solution. Research was subsequently focused on KGdF4 synthesis, a potential material for 1.3 mu m optical amplifiers when doped with Pr and Yb. Solubility and P-V-T measurements were used to determine conditions for the formation of KGdF4 single crystals doped with either Pr or Pr + Yb. Absorbance and fluorescence of these crystals are reported and compared with those for heavy metal fluoride glasses. These dopants were chosen in order to produce luminescence at a wavelength of 1.3 mu m, an important wavelength for optical amplifiers for optical fiber communication. Energy transfer from Yb to Pr was demonstrated and concentration quenching occurred only at similar to 10 x the concentration seen for rare earths in glass hosts. The results can be used as a guide for co-doping other fluorides and for growing larger crystals of KGdF4.