Light-induced polaronic absorption at low temperature in pure and (Fe, Ce, Cr) doped SrxBa1-xNb2O6 or Ba1-yCayTiO3 crystals and photodissociation of VIS centers into small polarons
|Stichwörter:||(BCT) barium-calcium-titanate; (SBN) strontium-barium-niobate; charge transfer model; DEFECT; DIELECTRIC-PROPERTIES; light-induced absorption; light-induced dissociation; NB4+ POLARONS; NIR ABSORPTION; Nuclear Science & Technology; PHOTOREFRACTIVE PROPERTIES; Physics; Physics, Condensed Matter; Physics, Fluids & Plasmas; small polarons; STRONTIUM-BARIUM NIOBATE||Erscheinungsdatum:||2003||Herausgeber:||TAYLOR & FRANCIS LTD||Journal:||RADIATION EFFECTS AND DEFECTS IN SOLIDS||Volumen:||158||Ausgabe:||1-6||Startseite:||357||Seitenende:||362||Zusammenfassung:||
Congruent SBN and BCT crystals doped with Fe, Cr, Ce to enhance photorefractive properties, are investigated at low temperature (T>1 K) under illumination with Ar+- and Kr+-laser light. Light-induced absorption changes in a wide spectral range from UV to IR indicate photoinduced charge transfer processes from impurities to polaronic centers. Broad NIR absorptions (at about 0,7 eV) associated with Ti3+ polarons in BCT or with Nb4+ polarons in SBN are observed and their non-linear behaviour with illumination intensity, polarization and temperature is described on the basis of the simple model for the photo charge transport (in SBN: Ce3+ Nb5+ <----> Ce4++ Nb4+). A broad visible absorption VIS (at about 2 eV) appearing together with the NIR polarons, is shown by photodissociation (with a Kr+-laser) to consist at least partly of small polarons (in BCT and SBN).
9th Europhysical Conference on Defects in Insulating Materials, WROCLAW, POLAND, JUL 01-05, 2002
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