Reflectance of Co- and Nb-doped BaTiO3 for photon energies from 1.8 to 70 eV

The reflectance spectra of Co- and Nb-doped BaTiO3 crystals have been measured for photon energies from 1.8 to 70 eV. For both types of crystal, structures observed in the 1.8 to 2.3 eV range can be attributed to the presence of residual impurities. Between 2.3 and 3.2 eV the peaks in the reflectance of the Co-doped crystal are found to be of an acceptor charge transfer type. For Nb-doped crystals structures appear at the bottom of the conduction band. For energies larger than 3.2 eV the spectra are characteristic of pure BaTiO3 crystals, in reasonable agreement with those determined by Baeuerle et al. and calculated by Michel-Calendini and Moretti. 15 refs., 4 figs., 1 tab