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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 9: Focus: Polar oxide crystals and solid solutions
KFM 9.9: Vortrag
Mittwoch, 18. März 2020, 12:30–12:50, TOE 317
A high-temperature optical spectroscopy study of lithium niobate, LiNbO3 — •Klaus-Dieter Becker1, Jianmin Shi1, Holger Fritze2, Günter Borchardt2, and Steffen Ganschow3 — 1TU Braunschweig, Institute of Physical and Theoretical Chemistry, 38106 Braunschweig, Germany — 2Clausthal University of Technology, 38640 Goslar, Germany — 3Leibniz Institute for Crystal Growth, 12489 Berlin
Optical absorption spectra of chemically reduced LN are dominated by broad bands in the visible and NIR region which have been attributed to various types of electron small polarons, see e.g. Ref. [1]. At 1000 ∘C, spectra measured under such conditions are dominated by an absorption band centered at about 0.9 eV due to free small polarons, i.e. due to electrons localized on niobium ions on regular sites. Band intensity has been found to follow a power law dependence on oxygen partial pressure PO2 of the form (PO2)m with m = 0.23 ± 0.01. This m-value is in excellent agreement the value of 1/4 predicted on the basis of point defect thermodynamics for the proposed chemical reduction model of LN. The experimental kinetics of reduction and oxidation processes upon oxygen activity jumps have been found to provide a non-conventional route to diffusion of lithium vacancies as well as to lithium ions in c-LN.
[1] O.F. Schirmer, M. Imlau, C. Merschjann, B. Schoke, J. Phys. Condens. Matter, 21 (2009) 123201.