Becker, Klaus-Dieter

Borchardt, Günter

Fielitz, Peter

Fritze, Holger

Schulz, Michael

Shi, Jianmin

Swanson, Claudia H.

English

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diffusion-fundamentals   The Open-Access Journal for the Basic Principles of Diffusion Theory, Experiment and Application www.diffusion-fundamentals.org, ISSN 1862-4138; © 2005-2010   Diffusion Fundamentals 12 (2010) 48  © C. H. Swanson Examinations of High-Temperature Properties  of Stoichiometric Lithium Niobate Claudia H. Swanson,*,1 Michael Schulz,1 Holger Fritze,1 Jianmin Shi,2 Klaus-Dieter Becker,2 Peter Fielitz,3 Günter Borchardt3 1 TU Clausthal, LaserAnwendungsCentrum, Am Stollen 19, 38640 Goslar, Germany  2 TU Braunschweig, Institut für Physikalische und Theoretische Chemie, Hans-Sommer Str.10, 38106 Braunschweig, Germany 3 TU Clausthal, Institut für Metallurgie, Robert-Koch Str. 42,  38678 Clausthal-Zellerfeld, Germany  E-Mail: claudia.swanson@tu-clausthal.de   Presented at the Bunsen Colloquium: Spectroscopic Methods in Solid State Diffusion and Reactions September 24th − 25th, 2009, Leibniz University Hannover, Germany  Non-stoichiometric lithium niobate has lithium contents of 46 ‒ 49 % Li2O and can be applied for surface acoustic wave devices and guided-wave optics because of its excellent piezoelectric and opti-cal properties, respectively. However, when non-stoichiometric lithium niobate is heated to higher temperatures, the lithium content in the crystal decreases leading to its decomposition. Lithium niobate with stoichiometric ratios of lithium and niobium was prepared by different research groups [1,2]. Several companies supplied samples for the experiments, all of which promised a lithium content of 50 % Li2O; DelMar Photonics (USA), Crystal Technology (USA), OXIDE (J) and Hungarian Acade-my of Sciences (H). An analysis of the lithium content in the different samples is performed using UV-Vis spectros-copy. The absorption edge for the absorptivity of lithium niobate at α = 20 cm−1 is known to give in-formation about the lithium content in the sample [3,4]. Fig. 1 shows the results for the different sam-ples and their lithium content determined from the absorption edge. For the analysis of lithium loss from high-temperature treatment, the crystals were heated to 900 °C in ambient air for 24 h.  Absorp-tion measurements and secondary ion mass spectroscopy indicate no lithium loss within the accuracy of the instruments [5]. Samples with 49.0 % Li2O (Del Mar) and 49.7 % Li2O (CrysTech) are analyzed using impedance spectroscopy in order to determine the electrical conductivity.  Fig. 2 shows the temperature dependent conductivity graph and the different activation energies of the lithium niobate samples.  The sample containing less lithium has an activation energy 0.29 eV greater than the samples with higher lithium content (for T ≤ 750 °C). The difference in conductivity might be related to oxygen vacancies in the lattice and explained by the following equation involving antisite defects: Nb O 3 4 Nb O 3Nb 2O Li NbO Li 2V 2LiNbO′′′′+ + + +  The preliminary results underline the potential of stoichiometric LiNbO3 for high-temperature applica-tions. Detailed investigations of transport phenomena, defect chemistry and electromechanical proper-ties will be performed as subject of an ongoing research project.  C. H. Swanson et al., High-temperature properties of LiNbO3  diffusion-fundamentals    www.diffusion-online.org  Diffusion Fundamentals 12 (2010) 49  © C. H. Swanson  Fig. 1  Li2O content of different lithium niobate samples determined from the absorption edge (α = 20 cm−1).    Fig. 2  Temperature dependence of the ionic conductivity for LiNbO3 with different Li2O contents.  References [1] D. Jundt, M. Fejer, R. Norwood, P. Bordui, J. Appl. Phys. 72 (1992) 3468.  [2] K. Polgár, Á. Péter, L. Pöppl, M. Ferriol, I. Földvári, J. Cryst. Growth 237 (2002) 682. [3] Y. L. Chen, J. P. Wen, Y. F. Kong, S. L. Chen, W. L. Zhang, J. J. Xu, G. Y. Zhang, J. Cryst. Growth 242 (2002) 400.  [4] M. Wöhlecke, G. Corradi, K. Betzler, Appl. Phys. B: Lasers and Optics, Springer 1996, 63, 323.  [5] G. Ohlendorf, D. Richter, J. Sauerwald, H. Fritze, Diff. Fundam. 8 (2008) 6.1 

Examinations of high-temperature properties of stoichiometric lithium niobate

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Examinations of high-temperature properties of stoichiometric lithium niobate

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