Instrumental neutron activation and absorption spectroscopy of photorefractive strontium-barium niobate single crystals doped with cerium

Abstract

Instrumental neutron activation analysis (INAA) was applied to determine the compositions of Sr x Ba 1− x Nb 2O 6: Ce single crystals with x = 0.61, grown from a melt with concentrations of cerium oxide ranging from 0.1 to 1.6 wt%. A decrease of the Ce-crystal-melt distribution coefficient ( C Ce,crystal C Ce,melt ), from 0.93 to 0.58, with increasing Ce concentrations in the melt was found. Furthermore, an increase of the Ba Sr concentrationratios ( C Ba C Sr ) by (14 ± 1%) from the crystal with the lowest to the sample with the highest Ce content is observed. With the assumption of a constant Nb concentration in all SBN-crystals the experiments reveal an increase of the C Ba C Nb ratio by (4 ± 2)% and a decrease of the C Sr C Nb ratio by (7 ± 2)% with increasing Ce concentration in the melt. This produces a shift of the parameter x in the SBN: Ce-formula from 0.61 to 0.57 ± 0.02. The opposite trend in the C Ba C Nb and the C Sr C Nb ratios with increasing Ce contents of the crystals indicates that Ce occupies Sr positions. The absorption coefficient α e for extraordinarily polarized light increases linearly with the increasing concentration C Ce,crystal of Ce in the crystal.