Hydrogen In Yttrium Research Articles

The Effect of Pressure Variations on the Electronic Structure, Phonon, and Superconducting Properties of Yttrium Hydrogen Selenide Compound

The Effect of Pressure Variations on the Electronic Structure, Phonon, and Superconducting Properties of Yttrium Hydrogen Selenide Compound

Doping and Pressure Effects on Yttrium Hydrogen Selenide

In this paper, the structural, electronic, phonon, and optical properties of lanthanum (La)‐doped yttrium hydrogen selenide (YHSe), along with the effects of pressure variations on its optical properties, are investigated using the density functional theory method. Both the La‐doped and YHSe systems are dynamically stable, as indicated by phonon calculations showing no imaginary frequencies in the Brillouin zone (BZ). The influence of pressure on optical properties is examined, revealing that increased pressure enhances these properties, particularly by improving the absorption coefficient in the ultraviolet (UV) range. Moreover, the bandgap energy of both La‐doped YHSe and YHSe compounds is explored. Increasing La concentration reduces the bandgap and enhances the density of states (DOS) at Fermi energy, inducing metallic characteristics in YHSe. Furthermore, the optical properties are examined at various La concentrations, most of which exhibit a nonlinear relationship as the La concentration increases. Doping under extreme conditions significantly enhances the optical properties of La‐doped YHSe, particularly in the UV‐light wavelength range. Specifically, the absorption coefficient reaches its maximum value in the energy range of 6.678 −13.023 eV within the UV region for all concentrations, indicating strong absorption in this range. This suggests the material’s effectiveness in absorbing electromagnetic radiation, particularly in the UV range, making it a promising candidate for photochromic applications. A thorough exploration of the optical properties under doping reveals prominent peaks, particularly in response to the UV spectrum, with a slight shift toward higher energies beyond the UV range. This suggests that the material under study holds promise as a candidate for sustained photochromic performance over time.

Experimental investigation and thermodynamic assessment of the yttrium-hydrogen binary system

A coupled experimental investigation and thermodynamic study of the yttrium-hydrogen (Y-H) binary system were carried out to provide more comprehensive and quantitative insights into the key thermodynamic properties of this system. Y-H system in the full range of H/Y = 0–3.0 was investigated by accurate pressure composition isotherm (PCI) measurement to provide credible phase equilibria information and thermodynamic data. The phase boundaries obtained were in agreement with previous experimental data but with improved accuracy. With the guide of the crystal structures, all the solid phases were modelled using the three sublattice model. The Y-H phase diagram and thermodynamic parameters were calculated and assessed with the CALPHAD technique. The obtained results are in very good agreement with our experimental data and the published data reported in literature. The obtained thermodynamic database of Y-H system can be used to predict the hydrogenation behavior and decomposition temperatures of hydrides.

Phase transformation in an yttrium–hydrogen system studied by TEM

Phase transformations in Pd-capped epitaxial yttrium films grown on (0 0 0 1) sapphire substrates covered with a Ti buffer layer and hydrogenated for different times were studied using transmission electron microscopy (TEM). For short hydrogen charging times, the phase transformation from α-Y to β-YH 2 is associated with the nucleation and growth of two orientational variants, which after coalescence form twin-related lamellae of the β-YH 2 phase with twin interfaces parallel to the substrate plane. Shockley partial dislocations are present at the twin boundaries; their glides during phase transformation are responsible for the formation of the twin lamellae. Superlattice reflections were observed for β-YH 2, and the existence of a new long-range ordered superstoichiometric YH 2+ x phase was suggested. A structural model of the ordering based on the occupation of octahedral interstitial sites by H in a doubled cell of Y-face-centered cubic was offered. For samples hydrogenated for longer times, β-YH 2-to-γ-YH 3 phase transformation was accompanied by cracking along the twin boundaries, which eventually developed into a network of pores and caused significant swelling of the films. No γ-YH 3 phase was observed directly in TEM because of its unstable nature under the high vacuum of a microscope column. The fully transformed YH 3 films have over a 60% increase in its thickness, which is mostly accounted for by the high volume fraction of pores.

Mechanical properties of yttrium hydrogen solid solution

The mechanical properties of yttrium hydrogen solid solution (0–0.20 H/Y) were studied to reveal the influence of hydrogen on the characteristics of yttrium. The elastic moduli such as Young's modulus and the shear modulus for yttrium hydrogen solid solution increased with increasing of hydrogen content. The microhardness for the solid solution was also increased with increasing of hydrogen content. The electronic structure of the yttrium hydrogen solid solution was evaluated by a first principle molecular orbital calculation. The mechanical properties of yttrium hydrogen solid solution were discussed in terms of the calculation results.

KYHP 3O 10: Rietveld refinement using X-ray powder diffraction data and Raman study of the conductivity phase transition

Potassium yttrium hydrogen triphosphate (KYHP 3O 10) crystallises in the triclinic system P1̄ at room temperature with the following parameters: a=6.8522(2), b=7.6254(2), c=8.5351(2) A ̊ , α=106.658(1), β=106.435(2) and γ=82.344(2)°; Z=2. This structure has been refined from X-ray powder diffraction data using the Rietveld method, with the isostructural compounds KSmHP 3O 10 and NH 4BiHP 3O 10 as the starting model. Refinement of 70 parameters by the Rietveld method, using 2447 reflections, led to cR wp=0.138, cR p=0.104 and R B=0.041. This compound is a chain-based structure. The K + and Y 3+ cations are intercalated between chains, formed of (HP 3O 10 4−) groups linked by OH⋯O hydrogen bonding along the c-axis. The yttrium atoms are in an eight-fold coordination and also build infinite chains of edge-sharing YO 8 polyhedra running parallel to the a-axis. The potassium cations are coordinated by 10 oxygen atoms and build chains of KO 10 polyhedra running parallel to the b-axis. A calorimetric study of the title compound shows one endothermal peak, which is detected at 519 K. Samples were examined by impedance and Raman spectroscopy techniques. The Raman spectra of KYHP 3O 10, recorded at different temperatures in the frequency range 50–1250 cm −1 show the presence of a transition, which is characterised by an unusual high conductivity caused by breaking of the hydrogen bridges and suggests a great dynamic disorder of protons. This permits H + ions at high temperature to contribute with the potassium cations to the ionic conductivity of the product.

Migration of hydrogen in yttrium at low temperatures

Abstract The migration of hydrogen atoms in yttrium (YH 0.05 ) is investigated by electrical resistance measurement around 150 K. The disordered hydrogen atoms are introduced by the quench from 273 K into liquid nitrogen and the hydrogen atoms are ordered by the migration of the atoms during the annealings. The activation energy of hydrogen migration is obtained from the kinetic analysis of the resistance decrease due to the ordering during the isochronal or isothermal annealings. The energy is determined more precisely by the isothermal annealings. The value, 0.481±0.005 eV (46.4±0.5 kJ/mol) is smaller than the high temperature values. The decrease of the value is caused by the tunnel effects of diffusion.

Hydrogen and deuterium in epitaxial Y(0001) films: Structural properties and isotope exchange

Hydrogen in yttrium is of fundamental interest as a model system for driving metal-insulator transitions including switchable optical properties from reflecting to transparent in the visible region. We report on the structural properties of hydrogenated and deuterated thin, monocrystalline Y(0001) films grown by molecular beam epitaxy on Nb/${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ substrates. X-ray diffraction reveals the response of the host metal lattice upon hydrogen loading. The structural coherence in all three spatial directions as well as the epitaxial relation to the substrate are maintained, though the sample undergoes structural phase transitions between the different hydride phases. With neutron reflectivity measurements we have determined the hydrogen and deuterium content since the critical angle for total reflection depends on their concentration in the sample. Measurements on hydrogenated and deuterated films show that H and D are completely interchangeable within the trihydride phase. Neutron scattering also allows us to determine the position of the deuterium atoms within the yttrium matrix. All structural information gained on thin films is in agreement with the space group $P3\ifmmode\bar\else\textasciimacron\fi{}c1$ which was previously determined from powder samples.

Theoretical Study of the Binding Properties and Electronic Structure of Hydrogen in Yttrium*

Theoretical Study of the Binding Properties and Electronic Structure of Hydrogen in Yttrium*

Hydrogen in yttrium via first-principles total-energy calculations.

The potential-energy surface of hydrogen in \ensuremath{\alpha}-${\mathrm{YH}}_{\mathit{x}}$ is obtained from first-principles total-energy calculations for the case of ${\mathrm{YH}}_{0.5}$. Results on the localized vibration frequencies of hydrogen, the splitting of the hydrogen energy level, and the activation energy for hydrogen diffusion are presented and compared with available experimental data.

Theoretical Study of the Binding Properties and Electronic Structure of Hydrogen in Yttrium*

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A Study of the Dynamics of Hydrogen in Yttrium Using Inelastic Neutron Scattering*

A Study of the Dynamics of Hydrogen in Yttrium Using Inelastic Neutron Scattering*

Concentration and temperature dependence of hydrogen vibrations along the c axis for hydrogen in yttrium: Evidence of dynamically coupled hydrogen pairs.

The c-axis vibrations of hydrogen in yttrium have been measured at various concentrations and temperatures using high-resolution neutron spectroscopy. The unusual splitting of these modes is revealed to be highly sensitive to both conditions and to isotopic dilution. The results indicate that the splitting is caused by hydrogen pairs dynamically coupled across metal atoms and that this interaction is modulated by concentration- and temperature-dependent occupation correlations along the c axis.

Formation of a novel yttrium hydride with bridging 1,2,3,4-tetramethylfulvene and hydride ligands

Thermolysis of [(C5Me5)2YH]2 in n-octane or benzene yields (C5Me5)2Y(µ-H)Y(η5-C5Me4CH2)(C5Me5), a bis-yttrium-monohydride in which a tetramethylfulvene ligand bridges in a σ–η5 manner between the yttrium atoms; the hydride bridge is asymmetric showing two yttrium–hydrogen coupling constants in the 1H n.m.r. spectrum.

Diffusivities of hydrogen in yttrium and yttrium alloys

Diffusivities of hydrogen in yttrium, yttrium-niobium (Y-Nb) alloy (3:7), yttrium-niobium (Y-Nb) composite (3:7), and yttrium-thorium (Y-Th) alloy (4:1) in the Sieverts region were measured by gas absorption in the temperature range from 960 to 1160 K. The diffusivity of hydrogen in yttrium was found to be D(cm 2/s) = 300 exp(−160,000/RT) , where R = 8.314 JδK −1δmol −1 . Above 1000 K, diffusivities are in the following order: D(Y-Nb composite) > D(Y-Nb alloy) > D(Y-Th alloy) > D(Y), where D(Y-Nb composite) = 2.4 D(Y) and D(Y-Nb alloy) = 1.5 D(Y). Below 1000 K, effective diffusivities of the alloys become quite erratic and fa11 below those for yttrium.

ChemInform Abstract: HIGH TEMPERATURE THERMODYNAMICS OF THE YTTRIUM‐HYDROGEN SYSTEMS

AbstractKalorimetrische Untersuchungen des Titelsystems bei 919 K und Drücken bis zu 1 at führen zu einer Bildungsenthalpie für YH, von ‐5 2.8 kcal mol‐1 . Die Übereinstimmung mit einigen früheren Gleichgewichtsuntersuchungen ist sehr gut.

High temperature thermodynamics of the yttrium–hydrogen systems

The binary system, yttrium–hydrogen, has been studied at 919 K at pressures up to 1 atm by a calorimetric–equilibrium method. From the calorimetric measurements we found the enthalpy of formation of YH2 at 919 K to be −52.8±0.4 kcal mole−1. The calorimetric results are in very good agreement with some of the enthalpies reported in a recent equilibrium investigation. Comparisons between the calorimetric measurements and the available equilibrium data provide new information on the partial entropy of hydrogen both in close packed hexagonal yttrium, and in the nonstoichiometric dihydride YH2−δ. For both phases we find the partial excess entropy of hydrogen near 1000 K to be about +5 cal mole−1 K−1; this value is essentially fully accounted for by the vibrational entropy contributions of hydrogen.

High temperature equilibrium measurements of the yttrium–hydrogen isotope (H2, D2, T2) systems.

Equilibrium pressures as a function of concentration and temperature were measured for the systems, yttrium–hydrogen, yttrium–deuterium, and yttrium–tritium. Temperatures were varied from 700–1000 °C and concentrations in the solid yttrium phase ranged from H/Y or D/Y atom ratios of 0.01 to 2.0 and T/Y ratios of 0.03 to 1.1. Equilibrium isotherms have been plotted and Van’t Hoff isopleths calculated for these systems. Relative partial molal enthalpies and entropies have been tabulated for the reactions of the hydrogen isotopes with yttrium as a function of atom ratio in the solid. In the low concentration range (H/Y=D/Y=T/Y&amp;lt;0.3), the data obey Sieverts law where the concentration of hydrogen isotope in yttrium is proportional to the square root of the hydrogen isotope pressure. Sieverts constants have been derived. At constant atom fraction the tritium compound has the highest equilibrium pressure and the protium compound the lowest. Expressions for the isotopic hydrogen pressure ratios have been derived and agree well with a simple theoretical treatment in which the dissolved hydrogen atoms are regarded as independent oscillators held in tetrahedral potential wells in the yttrium lattice.

Wide-line proton magnetic resonance in the solid solution phase of the yttrium-hydrogen system

The proton magnetic resonance and its temperature dependence have been studied in the solid solution phase of the yttriumhydrogen system, yielding information on hydrogen locations and diffusion in yttrium metal and on the phase boundaries at 300 K of the two-phase, yttrium + yttrium dihydride, region.

Hydrogen in liquid alkali metals

The chemistry of liquid alkali metal-hydrogen solutions has been surveyed. Solubility data for hydrogen (<6 mol% H) and deuterium (<4 mol% D) in liquid lithium are reported, Li-H log S(mol% H) = 3.523 − 2308/T(°K) Li-D log S(mol% D) = 4.321 − 2873/T(°K), and the isotope effect considered. The hydrogen data are used to augment the LiLiH phase diagram and are compared with corresponding solubilities in sodium, potassium and eutectic NaK (78 wt.% K) alloy; data for rubidium and caesium are not available. The nature of the solute species and the concept of solvation in these solutions are also discussed.Investigations of interactions between hydrogen and non-metals in liquid alkali-metal solutions have shown that, whereas hydrogen and nitrogen act independently in lithium at 420 °C, hydrogen and oxygen interact in sodium at 400 °C according to the equilibrium: O2− + H−⇌ OH− + 2e−. Hydrogen-oxygen interactions in the other alkali metals are also considered and are rationalised in terms of the enthalpy changes of the corresponding solid-state reaction. Furthermore, yttrium has been shown to react, rapidly, with hydrogen dissolved in lithium at a relatively low temperature (400 °C) to form a mixture of a solid solution of hydrogen in yttrium and yttrium dihydride according to the reaction: Li(H) + Y → Li + Y(H) + YH2−x.