Some dielectric and optical properties of PbF2-codoped CaF2:YbF3 crystals

YbF3-doped and PbF2-codoped CaF2 crystals were grown using the vertical Bridgman method. The optical absorption spectra reveal the existence of both Yb2+ and Yb3+ ions. The Pb2+ ions modify the characteristic absorption peaks of the Yb2+ ions, but do not influence the Yb3+ ion peaks. The dielectric relaxation gives information about the impurity-defect aggregates. The obtained dielectric spectra show that for our low-YbF3-concentration samples, the main dipole complexes are NN type. The Pb2+ ions do not have an important influence on the dielectric spectra. The activation energy for the dipole reorientation and the relaxation time constant have been determined.