Local structure and dynamics of proton and hydride-ion conducting perovskite type oxides
Doctoral thesis, 2019
For the proton conducting BaZrxM1-xO3Hx materials, the investigations focused on the nature of the proton sites in polycrystalline powder samples and were performed using inelastic neutron scattering and infrared and Raman spectroscopy combined with computer simulations. The results reveal the presence of a distribution of different types of proton sites, which were virtually the same for all chemical compositions except for a high level (x ≥ 0.5) of In-doping. It is argued that the high In-doping results in the presence of additional proton sites located in distorted structural arrangements and which resemble those found in the hydrated form of the brownmillerite structured Ba2In2O5 system. It is also shown that the local environment for a specific proton changes over time due to the lattice vibrational dynamics. Additionally, thin-film samples were investigated by means of X-ray and neutron reflectivity and nuclear reaction analysis, with the aim to obtain details about the incorporation and distribution of protons in the samples. A key result is the observation of a thin (3-4 nm) proton-rich layer near to the surface of the films. This layer features proton sites characterized by relatively week hydrogen-bond interactions and a reduced proton mobility compared to the bulk of the film.
The studies on hydride-ion conducting BaTiO3-xHx materials focused on revealing the nature of the local environments of the hydride ions and were performed using inelastic neutron scattering techniques and computer simulations. It is found that the presence of oxygen vacancies in the proximity of the hydride ions significantly influences their local environments and the vibrational properties.
Chalmers, Physics, Materials Physics
Structure and Conductivity of Epitaxial Thin Films of In-Doped BaZrO3-Based Proton Conductors
Journal of Physical Chemistry C,; Vol. 120(2016)p. 28415-28422
Local structure and vibrational dynamics in indium-doped barium zirconate
Journal of Materials Chemistry A,; Vol. 7(2019)p. 7360-7372
L. Mazzei, A. Perrichon, A. Mancini, L. Malavasi, S. F. Parker, L. Börjesson, M. Karlsson, Local coordination of protons in acceptor doped barium zirconates
C. Eklöf-Österberg, L. Mazzei, E. Jedvik Granhed, G. Wahnström, R. Nedumkandathil, U. Häussermann, S. F. Parker, N. H. Jalarvo, L. Börjesson, M. Karlsson, Local structure and vibrational dynamics of metal hydride reduced BaTiO3
L. Mazzei, B. Grimm-Lebsanft, D. Rukser, F. Biebl, J. Andreasson, D. Pergolesi, L. Börjesson, M. A. Rübhausen, T. Lippert, M. Karlsson, Phonon spectra of pure and acceptor doped BaZrO3 investigated with resonance Raman spectroscopy
In this thesis, I investigated one of the most well-known groups of proton conducting perovskite oxides, BaZrO3 based materials, and another, novel, family of energy-relevant perovskite oxides, oxyhydrates BaTiO3-xHx. For the investigations I mainly used light- and neutrons-based techniques. The basic idea of these techniques is to send a beam, of light or neutrons, on a material, and to study how the beam is modified due to the interaction with it. In this way it is possible to obtain very important information about the position of the atoms (structure) and the way they move (dynamics) in the material.
I specifically looked at the relationship between local structure, i.e. the structure on nanometer scale, and the way hydrogen moves. This helped us to better understand the fundamental properties of proton conducting oxides, especially on the local scale, and how these are affected by the chemical composition of the materials. More generally, the novel insights provided by this work contribute to the understanding and further development of materials for energy application.
Other Materials Engineering
Condensed Matter Physics
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4577
lecture hall KA, Kemigården 4, Chalmers Tekniska Högskola
Opponent: Dr. Timmy Ramirez-Cuesta, Spallation Neutron Source, Oak Ridge National Laboratory, U.S.A.