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A unique demonstration with ball-rolling mechanisms has been developed to illustrate the basic principles of mass analyzers as components of mass spectrometers. Three ball-rolling mechanisms mimicking the currently used mass analyzers (i.e., a quadrupole mass filter, a magnetic sector, and a time-of- flight) have been constructed. Each mechanism was designed to separate balls with three different weights (representing three ionized analytes with different weights) in an attempt to imitate the separation process employed by real mass analyzers. This demonstration helped students understand the basic principles of mass analyzers.

We describe an activity that is suitable for high school students and makes use of plastic bottles. This activity allows students to familiarize themselves with gas chemistry by introducing technologies that were applied in old submarine systems. Plastic bottles, which are representative of submarines, are used as reaction vessels. Three simple experiments regarding gas chemistry are carried out in the plastic bottles: (1) a carbon dioxide absorption reaction using soda lime, which mimics an air-cleaning canister; (2) a chlorine and hydrogen evolution reaction by the electrolysis of brine, which highlights the accidental generation of gases by lead batteries on board submarines; and (3) a catalytic hydrogen peroxide decomposition that exists in submarine propulsion system. To introduce an antisonar countermeasure system outside the submarine, a fourth experiment on hydrogen generation by the reaction of calcium hydride and water is also conducted.

Hydride ion conductors have made remarkable progress in recent years; in particular, the fluorite‐type LaH3‐δ series exhibits high conductivity around room temperature. However, its intrinsic character of hydrogen non‐stoichiometry still makes its application as a solid electrolyte challenging, for which high electronic insulation is essential. Here, Sr‐substituted LaH3‐δ with slight O2− incorporation, represented as La1‐xSrxH3‐x‐2yOy (0.1 ≤ x ≤ 0.6, y ≤ 0.171), is synthesized, which exhibits H− conductivity of 10−4 – 10−5 S cm−1 at room temperature. The galvanostatic discharge reaction using an all‐solid‐state cell composed of Ti|La1‐xSrxH3‐x‐2yOy|LaH3‐δ shows that the Ti electrode is completely hydrogenated to TiH2 for x ≥ 0.2, whereas a short circuit occurs for x = 0.1. These experimental observations, together with calculation studies on the density of states and the defect formation energy, provide clear evidence that electropositive cation, such as Sr, doping critically suppresses the electron conduction in LaH3‐δ. Achieving a superior H− conducting solid electrolyte is a novel milestone in the development of electrochemical devices that utilize its strong reducing ability (E°(H−/H2) = −2.25 V vs SHE), such as batteries with high energy density and electrolysis/fuel cells with high efficiency. [ABSTRACT FROM AUTHOR]

New solid compounds A3−xGaO4H1−y (A = Sr, Ba; x ∼0.15, y ∼0.3), which are the first oxyhydrides containing gallium ions, have been synthesized by high-pressure synthesis. Powder X-ray and neutron diffraction experiments revealed that the series adopts an anti-perovskite structure consisting of hydride-anion-centered HA6 octahedra with tetrahedral GaO4 polyanions, wherein the A- and H-sites show partial defect. Formation energy calculations from the raw materials support that stoichiometric Ba3GaO4H is thermodynamically stable with a wide band gap. Annealing the A = Ba powder under flowing Ar and O2 gas suggests topochemical H− desorption and O2−/H− exchange reactions, respectively. [ABSTRACT FROM AUTHOR]

K2NiF4‐type Ba–Li oxyhydride (BLHO) transitions to a so‐called hydride superionic conductor, exhibiting a high and essentially temperature‐independent hydride ion (H−) conductivity over 0.01 S cm−1 through the disordering of H− vacancies above 300 °C. In this study, a Ba–Li–Na–H–O oxyhydride system synthesized in which lithium is partially substituted with sodium in BLHO and investigated the effects of Na content on the phase transition behavior and the conductivity. Structural refinements and differential scanning calorimetry experiments confirmed a lowering trend in the phase transition temperatures and decreasing enthalpy changes for the transition with increasing Na content. Substitution of not <40% of Li with Na lowered the degree of ordered vacancies at the H− sites at room temperature and improved conductivities by more than two orders of magnitude in the low‐temperature region (T < 300 °C) before the phase transition. These findings clearly show that introducing Na into the lattice effectively stabilizes the high‐conductive phase of BLHO. [ABSTRACT FROM AUTHOR]

We report aliovalent partial substitution of Ba with K in Ba–Li oxyhydride, which exhibits a high H− conductivity caused by structural phase transitions. The phase transition temperatures were decreased by approximately 50 °C via 15% K/Ba substitution, resulting in a high conductivity at lower temperatures. [ABSTRACT FROM AUTHOR]

Barium titanium oxyhydride BaTiO3−xHx is a promising functional material that exhibits H−/e− mixed conduction. Here, for the first time, we report a direct synthesis of BaTiO3−xHx by a mechanochemical method. The as-prepared polycrystalline sample was able to work as a hydrogen permeable electrode. [ABSTRACT FROM AUTHOR]

A new layered perovskite oxyhydride Ba2YHO3 was synthesized via high pressure synthesis. Powder X-ray and neutron diffraction experiments revealed that in Ba2YHO3 the ordered H− and O2− anions form [Ba2H2] rock-salt layers wherein H− conduction is allowed. The conductivity reached 0.1 mS cm−1 at 350 °C, which is higher than that of isostructural Ba2ScHO3 with anion-disordered [Ba2HO] layers. [ABSTRACT FROM AUTHOR]

Recently, non-crystalline coordination materials have been shown to represent a versatile class of functional materials. However, such materials incorporating metal complex clusters have remained largely unexplored. Herein, we demonstrate that a luminescent tetranuclear ReV cluster melts at 489 K, with the cluster structure being maintained in the corresponding supercooled ionic liquid phase. [ABSTRACT FROM AUTHOR]

The high-pressure synthesis of a manganese oxyhydride LaSrMnO3.3H0.7 is reported. Neutron and X-ray Rietveld analyses showed that this compound adopts the K2NiF4 structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO4 that result in only oxygen-deficient phases down to LaSrMnO3.5. This suggests that high H2 pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition-metal oxyhydrides. Magnetic susceptibility revealed a spin-glass transition at 24 K that is due to competing ferromagnetic (Mn2+-Mn3+) and antiferromagnetic (Mn2+-Mn2, Mn3+-Mn3+) interactions. [ABSTRACT FROM AUTHOR]

Oxynitrides have been explored extensively in the past decade because of their interesting properties, such as visible-light absorption, photocatalytic activity and high dielectric permittivity. Their synthesis typically requires high-temperature NH3 treatment (800-1,300 °C) of precursors, such as oxides, but the highly reducing conditions and the low mobility of N3− species in the lattice place significant constraints on the composition and structure-and hence the properties-of the resulting oxynitrides. Here we show a topochemical route that enables the preparation of an oxynitride at low temperatures (<500 °C), using a perovskite oxyhydride as a host. The lability of H− in BaTiO3−xHx (x ≤ 0.6) allows H−/N3− exchange to occur, and yields a room-temperature ferroelectric BaTiO3−xN2x/3. This anion exchange is accompanied by a metal-to-insulator crossover via mixed O-H-N intermediates. These findings suggest that this 'labile hydride' strategy can be used to explore various oxynitrides, and perhaps other mixed anionic compounds. [ABSTRACT FROM AUTHOR]

Oxynitrides have been explored extensively in the past decade because of their interesting properties, such as visible-light absorption, photocatalytic activity and high dielectric permittivity. Their synthesis typically requires high-temperature NH3 treatment (800-1,300 °C) of precursors, such as oxides, but the highly reducing conditions and the low mobility of N3− species in the lattice place significant constraints on the composition and structure-and hence the properties-of the resulting oxynitrides. Here we show a topochemical route that enables the preparation of an oxynitride at low temperatures (<500 °C), using a perovskite oxyhydride as a host. The lability of H− in BaTiO3−xHx (x ≤ 0.6) allows H−/N3− exchange to occur, and yields a room-temperature ferroelectric BaTiO3−xN2x/3. This anion exchange is accompanied by a metal-to-insulator crossover via mixed O-H-N intermediates. These findings suggest that this 'labile hydride' strategy can be used to explore various oxynitrides, and perhaps other mixed anionic compounds. [ABSTRACT FROM AUTHOR]

Transition-metal oxyhydrides are an emerging class of functional materials; however, the known compounds have mostly been limited to perovskite-type sturctures. Here, we successfully synthesized Li 2 NbHO 2 , the first example of a rock-salt-type transition-metal oxyhydride, using mechanochemical methods. Galvanostatic charge/discharge tests revealed that Li 2 NbHO 2 functions as an electrode for lithium secondary batteries.

New solid compounds A 3- x GaO 4 H 1- y (A = Sr, Ba; x ∼0.15, y ∼0.3), which are the first oxyhydrides containing gallium ions, have been synthesized by high-pressure synthesis. Powder X-ray and neutron diffraction experiments revealed that the series adopts an anti-perovskite structure consisting of hydride-anion-centered HA 6 octahedra with tetrahedral GaO 4 polyanions, wherein the A- and H-sites show partial defect. Formation energy calculations from the raw materials support that stoichiometric Ba 3 GaO 4 H is thermodynamically stable with a wide band gap. Annealing the A = Ba powder under flowing Ar and O 2 gas suggests topochemical H - desorption and O 2- /H - exchange reactions, respectively.

K 2 NiF 4 -type Ba-Li oxyhydride (BLHO) transitions to a so-called hydride superionic conductor, exhibiting a high and essentially temperature-independent hydride ion (H - ) conductivity over 0.01 S cm -1 through the disordering of H - vacancies above 300 °C. In this study, a Ba-Li-Na-H-O oxyhydride system synthesized in which lithium is partially substituted with sodium in BLHO and investigated the effects of Na content on the phase transition behavior and the conductivity. Structural refinements and differential scanning calorimetry experiments confirmed a lowering trend in the phase transition temperatures and decreasing enthalpy changes for the transition with increasing Na content. Substitution of not <40% of Li with Na lowered the degree of ordered vacancies at the H - sites at room temperature and improved conductivities by more than two orders of magnitude in the low-temperature region (T < 300 °C) before the phase transition. These findings clearly show that introducing Na into the lattice effectively stabilizes the high-conductive phase of BLHO., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The introduction of chemical disorder by substitutional chemistry into ionic conductors is the most commonly used strategy to stabilize high-symmetric phases while maintaining ionic conductivity at lower temperatures. In recent years, hydride materials have received much attention owing to their potential for new energy applications, but there remains room for development in ionic conductivity below 300°C. Here, we show that layered anion-ordered Ba 2-δ H 3-2δ X ( X = Cl, Br, and I) exhibit a remarkable conductivity, reaching 1 mS cm -1 at 200°C, with low activation barriers allowing H - conduction even at room temperature. In contrast to structurally related BaH 2 (i.e., Ba 2 H 4 ), the layered anion order in Ba 2-δ H 3-2δ X , along with Schottky defects, likely suppresses a structural transition, rather than the traditional chemical disorder, while retaining a highly symmetric hexagonal lattice. This discovery could open a new direction in electrochemical use of hydrogen in synthetic processes and energy devices., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

A new layered perovskite oxyhydride Ba 2 YHO 3 was synthesized via high pressure synthesis. Powder X-ray and neutron diffraction experiments revealed that in Ba 2 YHO 3 the ordered H - and O 2- anions form [Ba 2 H 2 ] rock-salt layers wherein H - conduction is allowed. The conductivity reached 0.1 mS cm -1 at 350 °C, which is higher than that of isostructural Ba 2 ScHO 3 with anion-disordered [Ba 2 HO] layers.

Hydride (H - ) conduction is a new frontier related to hydrogen transport in solids. Here, a new H - conductive oxyhydride Ba 2 ScHO 3 was successfully synthesized using a high-pressure technique. Powder X-ray and neutron diffraction experiments investigated the fact that Ba 2 ScHO 3 adopts a K 2 NiF 4 -type structure with H - ions preferentially occupying the apical sites, as supported by theoretical calculations. Electrochemical impedance spectra showed that Ba 2 ScHO 3 exhibited H - conduction and a conductivity of 5.2 × 10 -6 S cm -1 at 300 °C. This value is much higher than that of BaScO 2 H, which has an ideal perovskite structure, suggesting the advantage of layered structures for H - conduction. Tuning site selectivity of H - ions in layered oxyhydrides might be a promising strategy for designing fast H - conductors applicable for novel electrochemical devices.

We synthesized a silver iron oxyfluoride AgFeOF 2 by using a high-pressure reaction. Synchrotron X-ray and neutron diffraction, X-ray absorption, and 57 Fe Mössbauer spectroscopy indicate that AgFeOF 2 crystallizes in the ideal perovskite structure with iron in a trivalent state, although electron microscopy revealed weak super-reflections. A possible partial ordering in the FeO 2 F 4 octahedron is inferred from Mössbauer spectroscopy. The synthesis of the fluorine-rich sample offers an opportunity to study a composition-property relation in AFe III O 3- n F n ( n = 0, 1, and 2). AgFeOF 2 exhibits a G-type antiferromagnetic ordering below T N ≈ 480 K, which is much lower than the n = 0 and 1 cases, suggesting a weaker superexchange interaction between Fe moments via F 2p orbitals (vs O 2p orbitals).

We investigated topochemical anion exchange reactions for a Sc III -substituted SrTi IV O 3 perovskite, Sr(Ti 1-y Sc y )O 3-y/2 □ y/2 (y ≤ 0.1), using CaH 2 . It was found that the initial introduction of a small amount of anion vacancies (y/2) is crucial to enhance the anion (H - /O 2- ) exchangeability. For example, hydride reduction of Sr(Ti 0.95 Sc 0.05 )O 2.975 yielded the oxyhydride SrTi 0.95 Sc 0.05 O 2.56 H 0.41 in which the hydride concentration is increased by 33% with respect to pristine SrTiO 3 (leading to SrTiO 2.76 H 0.24 ). This observation highlights the importance of anion vacancies to improve anion (H - /O 2- ) diffusion, which is a well-known strategy for improving oxide anion conductivity, and suggests that such a vacancy-assisted reaction could be applied to other anion exchange reactions (e.g., F - /O 2- and N 3- /O 2- ) to extend the solubility range.

We successfully synthesized the ternary bismuthides La 3 MBi 5 (M = Ti, Zr, Hf). These compounds crystallize in the hexagonal Hf 5 Sn 3 Cu-anti type structure (space group: P6 3 /mcm) consisting of face-sharing MBi 6 octahedral chains and hypervalent Bi linear chains, both separated by La atoms. Magnetic susceptibility and electrical resistivity measurements revealed that all of the compounds, including the solid solution La 3 Ti(Bi 1-x Sb x ) 5 , exhibit a Pauli paramagnetic behavior without any trace of superconductivity down to 1.85 K, as opposed to a recently reported 4 K superconductivity in La 3 TiSb 5 . The absence of superconductivity is supported by first-principles band calculations of La 3 TiBi 5 and La 3 TiSb 5 that demonstrate similar electronic structures with three-dimensional Fermi surfaces.

By using a high-pressure reaction, we prepared a new oxynitride ZnTaO 2 N that crystallizes in a centrosymmetric (R3̅c) high-temperature LiNbO 3 -type structure (HTLN-type). The stabilization of the HTLN-type structure down to low temperatures (at least 20 K) makes it possible to investigate not only the stability of this phase, but also the phase transition to a noncentrosymmetric (R3c) LiNbO 3 -type structure (LN-type) which is yet to be clarified. Synchrotron and neutron diffraction studies in combination with transmission electron microscopy show that Zn is located at a disordered 12c site instead of 6a, implying an order-disorder mechanism of the phase transition. It is found that the closed d-shell of Zn 2+ , as well as the high-valent Ta 5+ ion, is responsible for the stabilization of the HTLN-type structure, affording a novel quasitriangular ZnO 2 N coordination. Interestingly, only 3% Zn substitution for MnTaO 2 N induces a phase transition from LN- to HTLN-type structure, implying the proximity in energy between the two structural types, which is supported by the first-principles calculations.

We present how the introduction of anion vacancies in oxyhydrides enables a route to access new oxynitrides, by conducting ammonolysis of perovskite oxyhydride EuTiO3-xHx (x ∼ 0.18). At 400 °C, similar to our studies on BaTiO3-xHx, hydride lability enables a low temperature direct ammonolysis of EuTi(3.82+)O2.82H0.18, leading to the N(3-)/H(-)-exchanged product EuTi(4+)O2.82N0.12□0.06. When the ammonolysis temperature was increased up to 800 °C, we observed a further nitridation involving N(3-)/O(2-) exchange, yielding a fully oxidized Eu(3+)Ti(4+)O2N with the GdFeO3-type distortion (Pnma) as a metastable phase, instead of pyrochlore structure. Interestingly, the same reactions using the oxide EuTiO3 proceeded through a 1:1 exchange of N(3-) with O(2-) only above 600 °C and resulted in incomplete nitridation to EuTiO2.25N0.75, indicating that anion vacancies created during the initial nitridation process of EuTiO2.82H0.18 play a crucial role in promoting anion (N(3-)/O(2-)) exchange at high temperatures. Hence, by using (hydride-induced) anion-deficient precursors, we should be able to expand the accessible anion composition of perovskite oxynitrides.

Oxynitrides have been explored extensively in the past decade because of their interesting properties, such as visible-light absorption, photocatalytic activity and high dielectric permittivity. Their synthesis typically requires high-temperature NH3 treatment (800-1,300 °C) of precursors, such as oxides, but the highly reducing conditions and the low mobility of N(3-) species in the lattice place significant constraints on the composition and structure-and hence the properties-of the resulting oxynitrides. Here we show a topochemical route that enables the preparation of an oxynitride at low temperatures (<500 °C), using a perovskite oxyhydride as a host. The lability of H(-) in BaTiO3-xHx (x ≤ 0.6) allows H(-)/N(3-) exchange to occur, and yields a room-temperature ferroelectric BaTiO3-xN2x/3. This anion exchange is accompanied by a metal-to-insulator crossover via mixed O-H-N intermediates. These findings suggest that this 'labile hydride' strategy can be used to explore various oxynitrides, and perhaps other mixed anionic compounds.

The oxyhydride solid solutions (Ca,Sr)TiO(3-x)H(x) and (Sr,Ba)TiO(3-x)H(x) have been prepared by reducing the corresponding ATiO(3) oxides with calcium hydride. Under the reaction conditions examined, a hydride content of x = 0.1-0.3 was obtained for all compositions. Compared to our previous result with BaTiO(3-x)H(x), the larger particle size in this study (20-30 μm vs 170 nm) resulted in a somewhat lower hydride amount despite prolonged reaction times. We examined changes in cell volume, octahedral tilt angle, and site occupancy of different anion sites after conversion to oxyhydrides; it appears that these oxyhydrides fit the geometrical descriptions typical for regular ABO(3) perovskites quite well. The hydrogen release temperature, previously shown to be indicative of the hydride exchange temperature, however, does not scale linearly with the A-site composition, indicating a potential effect of chemical randomness.