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Instruments / Technical Area	Publication Details	Published
	Roadmap on inorganic perovskites for energy applications John Irvine , Jennifer Rupp , Gang Liu , Xiaoxiang Xu , Sossina M Haile , Xin Qian , Alem Snyder , Robert Freer , Dursun Ekren , Stephen Skinner , Ozden Celikbilek , Shigang Chen , Shanwen Tao , Tae Ho Shin , Ryan O'Hayre , Jake Huang , Chuancheng Duan , Meagan Papac , Shuangbin Li , Andrea Russell , Veronica Celorrio , Brian Hayden , Hugo Nolan , Xiubing Huang , Ge Wang , Ian Metcalfe , Dragos Neagu , Susana Garcia Martin Journal Of Physics: Energy DOI: 10.1088/2515-7655/abff18 Open Access Show Abstract ▼ Abstract: Inorganic perovskites exhibit many important physical properties such as ferroelectricity, magnetoresistance and superconductivity as well their importance as Energy Materials. Many of the most important energy materials are inorganic perovskites and find application in batteries, fuel cells, photocatalysts, catalysis, thermoelectrics and solar thermal. In all these applications, perovskite oxides, or their derivatives offer highly competitive performance, often state of the art and so tend to dominate research into energy material. In the following sections, we review these functionalities in turn seeking to facilitate the interchange of ideas between domains. The potential for improvement is explored and we highlight the importance of both detailed modelling and in situ and operando studies in taking these materials forward.	May 2021
B18-Core EXAFS	Revealing strain effects on the chemical composition of perovskite oxide thin films surface, bulk, and interfaces Celeste A. M. Van Den Bosch , Andrea Cavallaro , Roberto Moreno , Giannantonio Cibin , Gwilherm Kerherve , José M. Caicedo , Thomas K. Lippert , Max Doebeli , José Santiso , Stephen J. Skinner , Ainara Aguadero Advanced Materials Interfaces 247 DOI: 10.1002/admi.201901440 Diamond Proposal Number(s): [13530, 16839] Show Abstract ▼ Abstract: Understanding the effects of lattice strain on oxygen surface and diffusion kinetics in oxides is a controversial subject that is critical for developing efficient energy storage and conversion materials. In this work, high‐quality epitaxial thin films of the model perovskite La0.5Sr0.5Mn0.5Co0.5O3−δ (LSMC), under compressive or tensile strain, are characterized with a combination of in situ and ex situ bulk and surface‐sensitive techniques. The results demonstrate a nonlinear correlation of mechanical and chemical properties as a function of the operation conditions. It is observed that the effect of strain on reducibility is dependent on the “effective strain” induced on the chemical bonds. In‐plain strain, and in particular the relative BO length bond, is the key factor controlling which of the B‐site cation can be reduced preferentially. Furthermore, the need to use a set of complimentary techniques to isolate different chemically induced strain effects is proven. With this, it is confirmed that tensile strain favors the stabilization of a more reduced lattice, accompanied by greater segregation of strontium secondary phases and a decrease of oxygen exchange kinetics on LSMC thin films.	Dec 2019
I11-High Resolution Powder Diffraction	Phase evolution and reactivity of Pr2NiO4+δ and Ce0.9Gd0.1O2-δ composites under solid oxide cell sintering and operation temperatures Chen-Yu Tsai , Catriona M. Mcgilvery , Ainara Aguadero , Stephen J. Skinner International Journal Of Hydrogen Energy DOI: 10.1016/j.ijhydene.2019.10.011 Diamond Proposal Number(s): [19574] Show Abstract ▼ Abstract: In developing a new compositae air electrode for Solid Oxide Cells (SOCs) it is essential to fully understand the phase chemistry of all components. Ruddlesden-Popper type electrodes such as Pr2NiO4+δ have previously been proposed as attractive alternatives to conventional La0·6Sr0·4Fe0·8Co0·2O3-δ/Ce1-xGdxO2-δ compositae air electrodes for both fuel cell and electrolyser modes of operation. However, Pr2NiO4+δ have been shown to have limited stability, reacting with a Ce1-xGdxO2-δ interlayer to form a Ce1-x-yGdxPryO2-δ (CGPO) phase of unknown stoichiometry. Additionally, Pr2NiO4+δ are known to decompose to Pr4Ni3O10 ± δ under certain conditions. In this work detailed understanding of the chemical reaction between Pr2NiO4+δ and Ce0.9Gd0.1O2-δ (CGO10) under normal solid oxide cell fabrication and operating temperatures was obtained, identifying the composition of the resulting CGPO phase reaction products. It is shown that, in addition to the unreacted CGO10 present after sintering the compositae at 1100 °C for up to 12 h, a series of CGPO chemical compositions were formed with various Ce, Gd and Pr ratios depending on the relative distance of the doped ceria phases from the Pr2NiO4+δ phases. The extent of the chemical reaction was found to depend on the sintering time and the contact area of the two phases. Further thermal treatment of the resulting products under SOC air electrode operating temperature (800 °C) resulted in the initiation of Pr2NiO4+δ decomposition, forming Pr4Ni3O10 ± δ and Pr6O11 with no detectable change in the composition of previously formed Pr-substituted ceria phases. It is apparent that the Pr2NiO4+δ/CGO10 compositae is unsuitable as an air electrode, but there is evidence that the decomposition products, Pr4Ni3O10 ± δ and Ce1-x-yGdxPryO2-δ are stable and suitable candidates for SOC electrodes.	Nov 2019
B18-Core EXAFS	Redox behaviour and solid solubility of cerium ortho-niobates Cassandra M. Harris , Stephen J. Skinner Journal Of Solid State Chemistry 271, 135 - 143 DOI: 10.1016/j.jssc.2018.12.042 Diamond Proposal Number(s): [7943] Show Abstract ▼ Abstract: Using Ce LIII edge X-ray absorption near edge spectroscopy (XANES), it is shown that acceptor dopants introduced to cerium members of the rare earth ortho-niobate series, Ce1-xSrxNbO4±δ and Ce1-xCaxNbO4±δ, are charge compensated by the formation of holes on the cerium sublattice. These spectroscopic studies are complemented by structural studies, using X-ray and neutron powder diffraction, determining that the solubility limit of the strontium and calcium dopants within the CeNbO4+δ structure is ~10% and ~30% respectively. Under oxidising conditions, the Ce3+/Ce4+ redox couple facilitates reversible redox processes, and it is observed that the Ce1-xSrxNbO4±δ and Ce1-xCaxNbO4±δ materials form commensurate and incommensurately modulated oxygen hyperstoichiometric phases as a function of temperature. Under reducing atmospheres, this redox activity is suppressed, and charge-compensating Ce4+ holes are annihilated.	Mar 2019
I07-Surface & interface diffraction	Understanding surface structure and chemistry of single crystal lanthanum aluminate Stevin S. Pramana , Andrea Cavallaro , Jiahui Qi , Chris L. Nicklin , Mary P. Ryan , Stephen J. Skinner Scientific Reports 7 DOI: 10.1038/srep43721 Diamond Proposal Number(s): [11597] Open Access Show Abstract ▼ Abstract: The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.	Mar 2017
I11-High Resolution Powder Diffraction	Correlation of local structure and diffusion pathways in the modulated anisotropic oxide ion conductor CeNbO4.25 Stevin S. Pramana , Thomas Baikie , Tao An , Matthew G. Tucker , Ji Wu , Martin K. Schreyer , Fengxia Wei , Ryan D. Bayliss , Christian L. Kloc , Timothy J. White , Andrew P. Horsfield , Stephen J. Skinner Journal Of The American Chemical Society 138 (4), pp 1273–1279 DOI: 10.1021/jacs.5b11373 PMID: 26771687 Show Abstract ▼ Abstract: CeNbO4.25 is reported to exhibit fast oxygen ion diffusion at moderate temperatures, making this the prototype of a new class of ion conductor with applications in a range of energy generation and storage devices. To date, the mechanism by which this ion transport is achieved has remained obscure, in part due to the long-range commensurately modulated structural motif. Here we show that CeNbO4.25 forms with a unit cell ∼12 times larger than the stoichiometric tetragonal parent phase of CeNbO4 as a result of the helical ordering of Ce3+ and Ce4+ ions along z. Interstitial oxygen ion incorporation leads to a cooperative displacement of the surrounding oxygen species, creating interlayer “NbO6” connectivity by extending the oxygen coordination number to 7 and 8. Molecular dynamic simulations suggest that fast ion migration occurs predominantly within the xz plane. It is concluded that the oxide ion diffuses anisotropically, with the major migration mechanism being intralayer; however, when obstructed, oxygen can readily move to an adjacent layer along y via alternate lower energy barrier pathways.	Jan 2016
	Electronic and surface properties of Ga-doped In2O3 ceramics Anna Regoutz , Russell George Egdell , David J Morgan , Robert Palgrave , H. Téllez , Stephen Skinner , David Payne , G.w. Watson , David O. Scanlon Applied Surface Science 349, 970 - 982 DOI: 10.1016/j.apsusc.2015.04.106 Show Abstract ▼ Abstract: The limit of solubility of Ga2O3 in the cubic bixbyite In2O3 phase was established by X-ray diffraction and Raman spectroscopy to correspond to replacement of around 6% of In cations by Ga for samples prepared at 1250 °C. Density functional theory calculations suggest that Ga substitution should lead to widening of the bulk bandgap, as expected from the much larger gap of Ga2O3 as compared to In2O3. However both diffuse reflectance spectroscopy and valence band X-ray photoemission reveal an apparent narrowing of the gap with Ga doping. It is tentatively concluded that this anomaly arises from introduction of Ga+ surface lone pair states at the top of the valence band and structure at the top of the valence band in Ga-segregated samples is assigned to these lone pair states. In addition photoemission reveals a broadening of the valence band edge. Core X-ray photoemission spectra and low energy ion scattering spectroscopy both reveal pronounced segregation of Ga to the ceramic surface, which may be linked to both relief of strain in the bulk and the preferential occupation of surface sites by lone pair cations. Surprisingly Ga segregation is not accompanied by the development of chemically shifted structure in Ga 2p core XPS associated with Ga+. However experiments on ion bombarded Ga2O3, where a shoulder at the top edge of the valence band spectra provide a clear signature of Ga+ at the surface, show that the chemical shift between Ga+ and Ga3+ is too small to be resolved in Ga 2p core level spectra. Thus the failure to observe chemically shifted structure associated with Ga+ is not inconsistent with the proposal that band gap narrowing is associated with lone pair states at surfaces and interfaces.	Sep 2015
	Understanding the defect chemistry of alkali metal strontium silicate solid solutions: insights from experiment and theory Ryan D. Bayliss , Stuart N. Cook , David O. Scanlon , Sarah Fearn , Jordi Cabana , Colin Greaves , John A. Kilner , Stephen Skinner Journal Of Materials Chemistry A 2 (42), 17919 - 17924 DOI: 10.1039/C4TA04299A Show Abstract ▼ Abstract: Recent reports of remarkably high oxide ion conduction in a new family of strontium silicates have been challenged. It has recently been demonstrated that, in the nominally potassium substituted strontium germanium silicate material, the dominant charge carrier was not the oxygen ion, and furthermore that the material was not single phase (R. D. Bayliss et. al., Energy Environ. Sci., 2014, DOI: 10.1039/c4ee00734d). In this work we re-investigate the sodium-doped strontium silicate material that was reported to exhibit the highest oxide ion conductivity in the solid solution, nominally Sr0.55Na0.45SiO2.775. The results show lower levels of total conductivity than previously reported and sub-micron elemental mapping demonstrates, in a similar manner to that reported for the Sr0.8K0.2Si0.5Ge0.5O2.9 composition, an inhomogeneous chemical distribution correlating with a multiphase material. It is also shown that the conductivity is not related to protonic mobility. A density functional theory computational approach provides a theoretical justification for these new results, related to the high energetic costs associated with oxygen vacancy formation.	Sep 2014
I11-High Resolution Powder Diffraction	In situ compatibility studies of lanthanum nickelate with a ceria-based electrolyte for SOFC composite cathodes R. Sayers , J. E. Parker , C. C. Tang , S. J. Skinner Journal Of Materials Chemistry DOI: 10.1039/c2jm14384d Show Abstract ▼ Abstract: The phase stability and compatibility of intermediate temperature solid oxide fuel cell (IT-SOFC) composite cathodes of lanthanum nickelate, La2NiO4+δ (LNO), and ceria-gadolinium oxide, Ce0.9Gd0.1O2−δ (CGO10), have been investigated by high resolution synchrotron X-ray diffraction (XRD). No reaction was observed between LNO and CGO10 at temperatures of up to 900 °C when the composite is open to an ambient air environment. However, in a sealed capillary environment the 50[thin space (1/6-em)]:[thin space (1/6-em)]50 wt% LNO:CGO10 composite undergoes a partially reversible reaction at temperatures of 750 °C and above, whereby LNO decomposes to La2O3 and Ni. Changes in the CGO10 Bragg peaks indicate that this component is actively involved in this process. This study shows that the phase stability of LNO:CGO10 composites is highly dependent on oxygen partial pressure. In addition, it is observed that ex-situXRD is insufficient to determine the presence of reactivity in composite cathodes and that high resolution in situXRD measurements are required to obtain details of the complexity of phase stability in SOFC composite cathodes.	Jan 2012

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