Neutron Reflectivity in Corrosion Research on Metals.

Neutron reflectivity (NR) is potentially a powerful tool for characterizing chemical and morphological changes in thin films and at buried interfaces in corrosion science. While the scope of NR is limited by its inherent demands for low surface roughness and high sample planarity, these drawbacks are compensated for by the unique ability to detect light elements and distinguish between isotopes. Furthermore, the generally weak absorption of neutrons by matter allows the use of bulky sample environments and experiments.

Rotational Dynamics of Organic Cations in Formamidinium Lead Iodide Perovskites.

We report results from quasi-elastic neutron scattering studies on the rotational dynamics of formamidinium (HC[NH], FA) and methylammonium (CHNH, MA) cations in FAMAPbI with = 0 and 0.4 and compare it to the dynamics in MAPbI. For FAPbI, the FA cation dynamics evolve from nearly isotropic rotations in the high-temperature ( > 285 K) cubic phase through reorientations between preferred orientations in the intermediate-temperature tetragonal phase (140 K < ⩽ 285 K) to an even more complex dynamics, due to a disordered arrangement of the FA cations, in the low-temperature tetragonal phase ( ⩽ 140 K).

Promoting Persistent Superionic Conductivity in Sodium Monocarba--dodecaborate NaCBH via Confinement within Nanoporous Silica.

Superionic phases of bulk anhydrous salts based on large cluster-like polyhedral (carba)borate anions are generally stable only well above room temperature, rendering them unsuitable as solid-state electrolytes in energy-storage devices that typically operate at close to room temperature. To unlock their technological potential, strategies are needed to stabilize these superionic properties down to subambient temperatures. One such strategy involves altering the bulk properties by confinement within nanoporous insulators.

Diffusional Dynamics of Hydride Ions in the Layered Oxyhydride SrVOH.

Perovskite-type oxyhydrides are hydride-ion-conducting materials of promise for several types of technological applications; however, the conductivity is often too low for practical use and, on a fundamental level, the mechanism of hydride-ion diffusion remains unclear. Here, we, with the use of neutron scattering techniques, investigate the diffusional dynamics of hydride ions in the layered perovskite-type oxyhydride SrVOH. By monitoring the intensity of the elastically scattered neutrons upon heating the sample from 100 to 430 K, we establish an onset temperature for diffusional hydride-ion dynamics at about 250 K.

Cation Dynamics and Structural Stabilization in Formamidinium Lead Iodide Perovskites.

The vibrational dynamics of pure and methylammonium-doped formamidinium lead iodide perovskites (FAPbI) has been investigated by high-resolution neutron spectroscopy. For the first time, we provide an exhaustive and accurate analysis of the cation vibrations and underlying local structure around the organic moiety in these materials using first-principles electronic-structure calculations validated by the neutron data. Inelastic neutron scattering experiments on FAPbI provide direct evidence of the formation of a low-temperature orientational glass, unveiling the physicochemical origin of phase metastability in the tetragonal structure.

Neutron Scattering Investigations of the Global and Local Structures of Ammine Yttrium Borohydrides.

Complex metal hydrides are a fascinating and continuously expanding class of materials with many properties relevant for solid-state hydrogen and ammonia storage and solid-state electrolytes. The crystal structures are often investigated using powder X-ray diffraction (PXD), which can be ambiguous. Here, we revisit the crystal structure of Y(BD)·3ND with the use of neutron diffraction, which, in comparison to previous PXD studies, provides accurate information about the D positions in the compound.

Phonon spectra of pure and acceptor doped BaZrOinvestigated with visible and UV Raman spectroscopy.

We report results from visible and UV Raman spectroscopy studies of the phonon spectra of a polycrystalline sample of the prototypical perovskite type oxide BaZrOand a 500 nm thick film of its Y-doped, proton conducting, counterpart BaZrYO. Analysis of the Raman spectra measured using different excitation energies (between 3.44 eV and 5.

Hydride Reduction of BaTiO - Oxyhydride Versus O Vacancy Formation.

We investigated the hydride reduction of tetragonal BaTiO using the metal hydrides CaH, NaH, MgH, NaBH, and NaAlH. The reactions employed molar BaTiO/H ratios of up to 1.8 and temperatures near 600 °C.

Role of the doping level in localized proton motions in acceptor-doped barium zirconate proton conductors.

Acceptor-doped barium zirconates are currently receiving considerable interest because of their high proton conductivity at intermediate temperatures, making them applicable as electrolytes in various electrochemical devices, but the mechanism of proton conduction is unclear. Here, we investigate the role of the acceptor-dopant level in the localized proton motions, i.e.

Inorganic Phosphor Materials for Lighting.

This chapter addresses the development of inorganic phosphor materials capable of converting the near UV or blue radiation emitted by a light emitting diode to visible radiation that can be suitably combined to yield white light. These materials are at the core of the new generation of solid-state lighting devices that are emerging as a crucial clean and energy saving technology. The chapter introduces the problem of white light generation using inorganic phosphors and the structure-property relationships in the broad class of phosphor materials, normally containing lanthanide or transition metal ions as dopants.

The role of the ionic liquid C6C1ImTFSI in the sol-gel synthesis of silica studied using in situ SAXS and Raman spectroscopy.

The sol-gel synthesis of a silica based ionogel using the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C6C1ImTFSI) as the solvent has been followed in situ by combined μ-focused X-ray scattering and μ-Raman spectroscopy. By covering the momentum transfer range 0.2 < q < 30 nm(-1) we probe the evolution of the characteristic peaks of the ionic liquid, associated with the existence of polar and non-polar domains, as a function of reaction time.

Structural and vibrational properties of silyl (SiH3(-)) anions in KSiH3 and RbSiH3: new insight into Si-H interactions.

The alkali metal silyl hydrides ASiH3 (A = K, Rb) and their deuteride analogues were prepared from the Zintl phases ASi. The crystal structures of ASiH3 consist of metal cations and pyramidal SiH3(-) ions. At room temperature SiH3(-) moieties are randomly oriented (α modifications).

Proton dynamics in oxides: insight into the mechanics of proton conduction from quasielastic neutron scattering.

This article is concerned with the use of quasielastic neutron scattering as a technique for investigation of the dynamical properties of proton conducting oxides. Currently, the main interest in these materials comes from their promise as electrolytes in future electrochemical devices and particularly through their use as electrolytes in next-generation, intermediate-temperature, fuel cells. However, the realization of such devices depends critically on the development of new, more highly proton conducting oxides.

Perspectives of neutron scattering on proton conducting oxides.

Understanding the fundamental properties of materials of relevance for alternative energy technologies is crucial in addressing the global challenge of cleaner sources of energy. This Perspective article aims to demonstrate the important role that neutron scattering now plays in advancing the state of the art of the basic understanding of proton conducting oxides, which show potential as electrolytes in next-generation intermediate temperature fuel cells. In particular, the breadth of neutron scattering work on perovskite structured oxides, which continue to be the most promising class of electrolytes for intermediate-temperature applications, is reviewed.