Dynamics of Hydride Ions in Metal Hydride-Reduced BaTiO3 Samples Investigated with Quasielastic Neutron Scattering

Published

January 31, 2019

Author(s)

Carin Eklof-Osterberg, Reji Nedumkandathil, Ulrich Haussermann, Aleksander Jaworski, Andrew J. Pell, Madhu Sudan Tyagi, Niina H. Jalarvo, Bernhard Frick, Antonio Faraone, Maths Karlsson

Abstract

Perovskite-type oxyhydrides, BaTiO_3-xH^_x, have been recently shown to exhibit hydride ion (H^-) conductivity at elevated temperatures, but the underlying mechanism of hydride ion conduction and how it depends on temperature and oxygen vacancy concentration concentration remains unclear. Here we investigate, through the use of quasielastic neutron scattering techniques, the nature of the hydride ion dynamics in three reduced BaTiO₃ samples whihc are characterized by the simultaneous presence of hydride ions and oxygen vacancies. Measurements of elastic fixed window scans upon heating reveal the presence of quasielastic scattering due to hydride ion dynamics for temperatures above ca. 200 K. Analyses of quasielastic spectra measured at low (225 K and 250 K) and high (400 K to 700 K) temperature show that the dynamics can be adequately described by established models of jump diffusion, with a preference for the Chudley-Elliott model. At low temperature, less than or equal to}250 K, any of the models features a characteristic jump distance of about 2.8 angstrom} and thus of the order of the distance between successive jumps of the order of 0.1 nanoseconds. At higher temperatures, >400 K, the jump distance increases to about 4 angstrom} and thus of the order of the distance between next-nearest neighboring oxygen atoms or oxygen vacancies, and a mean residence time of the order of picoseconds. Diffusion constants D were computed from the data measured at low and high temperatures, respectively, and take on values of about 0.4 x 10^-6 cm^-2s^-1 at the lowest applied temperature of 225 K, and between ca. 20x10^-6 cm^-2s^-1 and 100x10⁰⁶ cm^-2su-1^ at temperatures between 400 K and 700 K. Activation energies E_a were derived from the measurements at high temperatures and take on values of about 0.1 eV and show a slight increase with increasing oxygen vacancy concentration.

Citation

Journal of Physical Chemistry C

Volume

123

Issue

4

Pub Type

Journals

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Keywords

neutron scattering, dynamics, hydride ions

Citation

Eklof-Osterberg, C. , Nedumkandathil, R. , Haussermann, U. , Jaworski, A. , Pell, A. , Tyagi, M. , Jalarvo, N. , Frick, B. , Faraone, A. and Karlsson, M. (2019), Dynamics of Hydride Ions in Metal Hydride-Reduced BaTiO₃ Samples Investigated with Quasielastic Neutron Scattering, Journal of Physical Chemistry C, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926177 (Accessed April 23, 2024)