Local structure and dynamics of proton and hydride-ion conducting perovskite type oxides
Doktorsavhandling, 2019
Proton and hydride-ion conducting oxides show potential for application in several technological devices, such as solid oxide fuel cells and batteries. However, fundamental properties pertaining to the local structure and conduction mechanisms in these materials are unclear. Such fundamental knowledge is crucial for the development of novel materials and, ultimately, for their application in technological devices. This thesis reports on investigations of local structure and dynamics in two families of hydrogen containing perovskite structured oxides, namely proton-conducting BaZrxM1-xO3Hx (M = In, Sc and Y, x ≤ 0.5) and hydride-ion conducting BaTiO3-xHx (x ≤ 0.15).
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.
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.
hydrogen
local coordination
vibrational dynamics
neutron scattering
vibrational spectroscopy
thin films
Perovskite oxides
lecture hall KA, Kemigården 4, Chalmers Tekniska Högskola
Opponent: Dr. Timmy Ramirez-Cuesta, Spallation Neutron Source, Oak Ridge National Laboratory, U.S.A.
Författare
Laura Mazzei
Chalmers, Fysik, Materialfysik
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
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Local structure and vibrational dynamics in indium-doped barium zirconate
Journal of Materials Chemistry A,; Vol. 7(2019)p. 7360-7372
Artikel i vetenskaplig tidskrift
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
The production of sustainable and clean energy is one of the most important challenges of our time, and it has motivated a great amount of research work in very different areas. Hydrogen fuel cells are amongst the most promising environmental-friendly devices, but their full exploit requires to develop novel components that satisfy the requirement for practical, every day, application. Of crucial importance is to find conducting materials (electrolytes) which can work between 200 and 500 °C and which show high conductivity. Among others, proton conducting oxides with so-called perovskite structure have emerged as some of the best candidates as electrolyte materials in this temperature range. Yet, in order to design materials tailored for application, one needs first to gain a better understanding of how protons move and how the properties of the material influence the way protons move.
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.
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.
Ämneskategorier
Oorganisk kemi
Materialkemi
Annan materialteknik
Den kondenserade materiens fysik
ISBN
978-91-7905-110-5
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4577
Utgivare
Chalmers
lecture hall KA, Kemigården 4, Chalmers Tekniska Högskola
Opponent: Dr. Timmy Ramirez-Cuesta, Spallation Neutron Source, Oak Ridge National Laboratory, U.S.A.