VARIATION OF LUMINESCENCE AND SECOND HARMONIC GENERATION OF DEFECT POLARIZATION CLUSTERS INDUCED BY REDUCTION IN PURE KTaO3 AND KTaO3:Fe

Autor(en): Horst, C. Auf Der
Magnien, S.
Kapphan, S.
Stichwörter: Materials Science; Materials Science, Multidisciplinary; Physics; Physics, Condensed Matter
Erscheinungsdatum: 1996
Herausgeber: TAYLOR & FRANCIS LTD
Journal: FERROELECTRICS
Volumen: 185
Startseite: 265
Seitenende: 268
Zusammenfassung: 
Nominally pure and Fe doped KTaO3 crystals were investigated by means of optical second harmonic generation (SHG) and luminescence. Reduction of KTaO3 (vacuum or H-2 atmosphere, T = 1000 degrees C) increases both, the luminecence intensity (lambda(max) approximate to 520 nm, lambda(exc) approximate to 340 nm) and the low temperature (T < 50 K) SHG intensity. Oxidation (02 atmosphere, p = 20 bar, T = 750 degrees C) leads to a vanishing of both, SHG and luminescence intensity. The results are interpreted in terms of inversion symmetry breaking dipolar defects associated with oxygen vacancies, inducing dipolar microregions in the highly polarizable KTaO3 host lattice. Fe doped crystals (5000 ppm Fe in the melt) do show essentially the same behavior with lower magnitude compared to the nominally pure KTaO3 in both the SHG and luminescence intensity. Therefore, low symmetry rhombic Fe3+ centers with neighbouring oxygen vacancies, suggested to be the origin of dipolar microregions, can not account for the drastic effects of reduction/oxidation treatments, whereas Ta3+ oxygen vacancy centers appear to be good candidates. Moreover it should be stressed that in well oxidized samples the effects of inversion symmetry breaking defects are seen to be minimized.
ISSN: 00150193
DOI: 10.1080/00150199608210529

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