SKM 2023 – scientific programme
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 13: Polar Oxide Crystals and Solid Solutions I
KFM 13.6: Talk
Thursday, March 30, 2023, 11:55–12:15, POT 106
A high-temperature optical spectroscopy study of lithium niobate, LiNbO3 — •Klaus-Dieter Becker1, Jianmin Shi1, Piotr Gaczynski1, Misha Sinder2, Uliana Yakhnevych3, Natalia Syvorotka3, Yuriy Suhak3, Steffen Ganschow4, and Holger Fritze3 — 1Institute of Physical and Theoretical Chemistry, TU Braunschweig, Braunschweig, Germany — 2Materials Engineering Department, Ben Gurion University of the Negev, Beer-Sheva, Israel — 3Institute for Energy Research and Physical Technologies, TU Clausthal, Goslar, Germany — 4Leibniz Institut für Kristallzüchtung, Berlin, Germany
Optical absorption spectra of chemically reduced LiNbO3 (LN) show broad bands in the vis and NIR region which have been attributed to various types of electron small polarons. At 1000°C, spectra are dominated by an absorption band at 0.9 eV due to free small polarons, i.e. 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(+-)0.02. This m-value is in excellent agreement with the value of -1/4 predicted from point defect thermodynamics of the chemical redox model of LN. The experimental kinetics of reduction and oxidation following a rapid change in oxygen partial pressure have been found to provide a novel route to diffusion of lithium vacancies at high temperatures as well as to that of lithium ions in LN.