Congruent Sr0.61Ba0.39Nb2O6 doubly doped with Ce and Cr: Photo- and thermoluminescence investigations

Abstract

Congruent Sr-x Ba1-xNb2O6 (SBN, x=0.61) doped with Ce or Cr ions exhibits enhanced photorefractive properties and new spectral features like increased red sensitivity. Here special emphasis is placed on the luminescence features of doubly doped Ce+Cr SBN crystals. The luminescence excitation and emission spectra combined with the absorption of the impurities allow to draw conclusions about the origin of the charge carriers und their recombination. The well separated thermo-luminescence peaks detected and their spectral line shape in emission point to specific recombination processes following the thermal liberation of light-induced electron trapping centers: Nb4+ polarons and VIS-centers created at low temperature under light irradiation. The thermal activation energy for the hopping motion of Nb4+ polarons and of VIS-centers are estimated to be 0.18+/-0.02 eV and 0.30+/-0.05 eV respectively. Possible excitation and recombination mechanisms in SBN:Ce+Cr are discussed.