REDUCTION OF THE IONIC-CONDUCTIVITY OF FLUX GROWN KTIOPO4 CRYSTALS

A mechanism and method for reducing the ionic conductivity of KTP crystals grown by the flux technique utilizing the doping of trivalent ions (Ga and Al) on the Ti site and tetravalent ions (Si) on the P site are described. Results are presented showing that, by using appropriate concentrations of these dopants added to the growth solutions, crystals can be grown over a range of growth temperatures which have ionic conductivities that are 1.5 to 3 orders of magnitude lower than undoped KTP crystals grown over similar temperatures. The dopant ion concentrations obtained in the crystals are consistent with the concentrations calculated, using the defect mechanism described, to achieve the observed ionic conductivity reductions. Distribution coefficients have been calculated for the dopants over a wide range of growth temperatures. The distribution coefficient for Ga in KTP appears to be relatively insensitive to concentration or temperature over a range of doping levels and growth temperatures. The use of doping is shown to also be effective in reducing the ionic conductivity of KTA crystals grown by the flux technique.