| 1. |
- Afif, A., et al.
(författare)
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Ceramic fuel cells using novel proton-conducting BaCe 0.5 Zr 0.3 Y 0.1 Yb 0.05 Zn 0.05 O 3-δ electrolyte
- 2022
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1433-0768 .- 1432-8488. ; 1:26, s. 111-120
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Tidskriftsartikel (refereegranskat)abstract
- Protonic ceramic fuel cells have become extremely interesting due to their high power output at the intermediate temperature range (400–700 °C). Significant progress has been made to develop electrolyte materials, doped barium cerates-zirconate, which gets the leading role due to its high chemical stability and high ionic conductivity. Here, we present a new composition BaCe0.5Zr0.3Y0.1Yb0.05Zn0.05O3-δ (BCZYYbZn05), where addition of 5 mol% Zn with Ce, Zr, Y, and Yb at the B-site of the perovskite material shows high stability with high conductivity. The material was synthesized by solid-state reaction route at 1400 °C which showed 98% relative density. Rietveld analysis of neutron powder diffraction data reveal an orthorhombic structure with Pbnm space group. Thermogravimetric analysis shows about 1.06% weight loss from 200 to 1000 °C which is mainly related to the formation of the oxygen vacancies. In wet hydrogen atmosphere, this material shows higher conductivity and lower activation energy than dry hydrogen atmosphere indicates the conduction type as protonic conduction. The anode-supported single test cell based on this electrolyte material demonstrates peak power densities 649 mW cm−2 at 700 °C using conventional BSCF cathode, representing an important step toward commercially viable SOFC technology.
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| 2. |
- Afroze, Shammya, 1987, et al.
(författare)
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Insight of novel layered perovskite PrSrMn2O5+δ: A neutron powder diffraction study
- 2020
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Ingår i: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 261
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Tidskriftsartikel (refereegranskat)abstract
- Neutron diffraction is very important to characterizing complex oxide materials, especially for the light element position and occupancy. In this study, a new layered perovskite oxide material, PrSrMn2O5+δ, was prepared by the solid-state reaction method and characterized by using X-ray and neutron powder diffraction, scanning electron microscopy and thermogravimetric analysis. X-ray diffraction data showed that the material adopted orthorhombic symmetry and Rietveld refinement of the neutron diffraction data gave accurate unit cell parameters (a = 3.8907 (1) Å, b = 3.8227 (1) Å, and c = 7.6846 (2) Å, atomic positions and space group (Pmmm)). Scanning electron microscopy showed a porous and interlinked microstructure. Thermogravimetric analysis exhibited two-stage weight losses up to 1000 °C from room temperature, indicating a good amount of oxygen losses and high material stability.
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| 3. |
- Afroze, Shammya, 1987, et al.
(författare)
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Neutron and X-ray powder diffraction data to determine the structural properties of novel layered perovskite PrSrMn2O5+δ
- 2020
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Ingår i: Data in Brief. - : Elsevier BV. - 2352-3409. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- The data presented in this article are related to the formation of a novel layered perovskite oxide material, PrSrMn2O5+δ, through a solid-state synthesis route. Here, we present the high-resolution neutron powder diffraction and the X-ray powder diffraction data at room temperature. The new perovskite material crystallizes in the orthorhombic symmetry. Interpretation of this data can be found in a research article titled “Insight of novel layered perovskite PrSrMn2O5+δ: A neutron powder diffraction study” (Shammya et al., 2019) [1].
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| 4. |
- Afroze, Shammya, 1987, et al.
(författare)
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Structure-conductivity relationship of PrBaMnMoO 6-δ through in-situ measurements: A neutron diffraction study
- 2021
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 47:1, s. 541-546
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Tidskriftsartikel (refereegranskat)abstract
- The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P21/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (<5%), an orthorhombic AB2O5 type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO4 in the tetragonal I41/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm−1 at 700 °C.
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| 5. |
- Perrichon, Adrien, 1988, et al.
(författare)
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Local Coordination Environments and Vibrational Dynamics of Protons in Hexagonal and Cubic Sc-Doped BaTiO3 Proton-Conducting Oxides
- 2020
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:16, s. 8643-8651
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Tidskriftsartikel (refereegranskat)abstract
- The proton local coordination environments and vibrational dynamics associated with the two order of magnitude change in proton conductivity in hydrated forms of hexagonal and cubic structured BaTi1-xScxO3Hx (0.16 < x < 0.7) were investigated using optical spectroscopy, neutron spectroscopy, and first-principles calculations. Whereas the cubic structure compositions display a single proton site, we show that protons occupy three distinct sites in compositions exhibiting the hexagonal structure. The principal site is characterized by interoctahedral hydrogen bonds, while two additional low occupancy sites are similar to those in the cubic structure, with classic intraoctahedral geometry. Furthermore, the proton hydrogen bond strength increases with decreasing scandium doping level. We infer from this that the stronger, more energetic hydrogen bonds in the hexagonal structure, resulting from proton sites with lower symmetry (lower multiplicity), are predominantly responsible for the significant reduction in macroscopic conductivity between cubic and hexagonal BaTi1-xScxO3Hx materials, rather than simply the absolute number of protons. Our findings are highly relevant to the field, clarifying the advantages of high-symmetry structures with high-multiplicity proton sites to favorable properties in ceramic proton-conducting oxides.
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| 6. |
- Torino, Nico, 1982
(författare)
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Beyond average crystal structures: understanding extended and local environments in proton-conducting Sc-substituted BaTiO3 perovskites
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proton conducting ceramics are very promising for applications concerned with energy sourcing with cleaner, safer, more abundant and cheaper alternatives to fossil fuels. These materials are still in development and advances in the field depend on a better understanding of the role of defects, their identification and location in the host framework, and the assessment of their short- and long-range dynamics and kinetics. With that aim, the work included in this thesis focussed on investigations of the effect of Sc substitution on the long- and short-range structure, oxygen vacancies and protons distribution, and their link to proton conductivity, in BaTiO3 materials. The system BaTi1–xScxO3–x/2 with x = ⅙, 20, 50 and 70 was studied with a combination of thermogravimetric, scattering, spectroscopic and computational methods. Neutron powder diffraction (NPD) provided the first representations of hexagonal and cubic members of the solid solution BaTiO3-Sc2O3. They revealed the different ordering of oxygen vacancies, protons and transition metal ions in the two structural types as a function of the Sc concentration and justified the large improvement in proton conductivity from hexagonal to cubic structures, due to the localised nature of protonic defects in the former. The combination of thermogravimetric and NPD methods applied simultaneously to study the dehydration of cubic members of the series suggested that vacancy-vacancy interactions are attenuated by higher Sc levels where the size difference between oxygen vacancy and protonic defect is larger. The Reverse Monte Carlo method revealed the local ordering of Ti in cubic types, a local symmetry-breaking effect that has repercussions on the physical properties of these materials, causing anomalously small volume changes upon hydration in low-Sc phases. Computer simulations, and spectroscopic methods employing radiation (IR, Raman) and neutrons (Inelastic Neutron Scattering) provided further insight into the structural features and offered a detailed characterisation of the proton sites and their dynamics, suggesting that higher Sc levels are associated to weaker hydrogen bonding and to configurations more favourable for proton transport. The present work contributed further understanding of the factors influencing proton transport in highly defective perovskite-structured materials. It was found that high Sc concentrations in the cubic host lattice of BaTiO3 yield highly stable phases where transport of protonic defects is favoured by a crystal site of high symmetry and multiplicity. Alongside the study of the peculiarities of the BTS system, recommendations for candidate systems identification and doping strategy were provided.
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| 7. |
- Torino, Nico, 1982, et al.
(författare)
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Insight into the dehydration behaviour of scandium-substituted barium titanate perovskites via simultaneous in situ neutron powder thermodiffractometry and thermogravimetric analysis
- 2018
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 324, s. 233-240
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Tidskriftsartikel (refereegranskat)abstract
- Hydration-dehydration cycles are critical to the mechanical performance of ceramic proton conductors. The development of in situ methods is desirable in order to study their structural response under conditions that mimic the operating ones. Neutron powder diffraction studies combined with simultaneous thermogravimetric analysis were performed on the hydrated forms of two members of the oxygen deficient perovskite BaTi1−xScxO3−δseries, with x = 0.5 and x = 0.7. Rietveld analyses agreed with in situ gravimetric data, allowing correlation of occupancy factors of the oxygen site to hydration levels and other structural data. Dehydration is an activated process that impacts on structural parameters and the level of Sc substitution was found to control the structural response during in situ dehydration, with higher Sc content leading to significantly greater volume contraction. This was rationalised by the chemical expansion due to hydration of oxygen vacancies within the x = 0.5 sample being anomalously small. Furthermore, the behaviour of the x = 0.5 system revealed an unexpected cell expansion during the early stages of dehydration, suggesting the hydration level may influence the thermal expansion coefficient (TEC).
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| 8. |
- Torino, Nico, 1982, et al.
(författare)
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The influence of cation ordering, oxygen vacancy distribution and proton siting on observed properties in ceramic electrolytes: the case of scandium substituted barium titanate
- 2017
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 46:26, s. 8387-8398
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Tidskriftsartikel (refereegranskat)abstract
- The origin of the 2-order of magnitude difference in the proton conductivity of the hydrated forms of hexagonal and cubic oxygen deficient BaScxTi1-xO3-delta (x = 0.2 and x = 0.7) was probed using a combination of neutron diffraction and density functional theory techniques to support published X-ray diffraction, conductivity, thermogravimetric and differential scanning calorimetry studies. Cation ordering is found in the 6H structure type (space group P6(3)/mmc) adopted by BaSc0.2Ti0.8O3-delta with scandium preferentially substituting in the vertex sharing octahedra (2a crystallographic site) and avoiding the facesharing octahedra (4f site). This is coupled with oxygen vacancy ordering in the central plane of the facesharing octahedra (O1 site). In BaSc0.7Ti0.3O3-delta a simple cubic perovskite (space group Pm3m) best represents the average structure from Rietveld analysis with no evidence of either cation ordering or oxygen vacancy ordering. Significant diffuse scattering is observed, indicative of local order. Hydration in both cases leads to complete filling of the available oxygen vacancies and permits definition of the proton sites. We suggest that the more localised nature of the proton sites in the 6H structure is responsible for the significantly lower proton conduction observed in the literature. Within the 6H structure type final model, proton diffusion requires a 3-step process via higher energy proton sites that are unoccupied at room temperature and is also likely to be anisotropic whereas the highly disordered cubic perovskite proton position allows 3-dimensional diffusion by well-described modes. Finally, we propose how this knowledge can be used to further materials design for ceramic electrolytes for proton conducting fuel cells.
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