Large Lattice Distortion Research Articles

Suppressing/enhancing effect of rhenium on helium clusters evolution in tungsten: Dependence on rhenium distribution

The influence of rhenium (Re) on helium (He) evolution in tungsten (W) with different Re distribution is investigated using the first-principles calculations in combination with thermodynamic models. It is found that the He behaviors in W-Re system are closely related to the Re distribution. For the dispersed distribution of Re in W, it is found that a single Re atom only has slight effect on the behaviors of a He atom due to the weak interaction of Re-He1. Interestingly, with the increasing of He numbers, the binding energy between a single Re and He clusters increases rapidly from 0.03 eV for Re-He1 to 0.72 eV for Re-He4. Such high binding energy indicates the strong attraction of Re with He clusters in W. This can be rationalized by the large lattice distortion induced by He clusters, which reduces the electron density of He-occupied position and leads to the transition of neighboring Re/W atom from a substitutional site to an interstitial site. Because of the strong attraction of Re with He clusters, the Re addition effectively reduce the mobility of He clusters in W. As for the aggregated Re distribution, the He trapping capability of vacancy is weakened by Re clusters. These results are well consistent with the experimental observed suppressing effects of Re on the He-induced morphology in W. Further, based on the He behaviors in W-Re σ phase, we suppose that He will segregate from bulk W to Re-rich precipitates, thus enhancing the formation of He clusters. Consequently, our calculations suggest that the distribution of Re plays a key role on the He behaviors in W, which provides a good reference for the design and development of W-based alloys.

Enhanced piezoelectric properties of 0.49Pb(Ni,Nb)O3–0.51Pb(Hf,Ti)O3 ceramics by ion pair doping

Based on the relaxation ferroelectric of 0.49Pb(Ni1/3Nb2/3)O3–0.51Pb(Hf0.3Ti0.7)O3 (0.49PNN–0.51PHT), the method generating structural defects by Li+ and Al3+ ion pair doping was proposed to improve the piezoelectric property. Results showed that the ion pairs facilitated the increase of tetragonal phase content in perovskite structure, and caused larger lattice distortion along the [001] direction. A high piezoelectric coefficient of d33 = 1040 pC/N was achieved for the 0.49PNN–0.51PHT ceramic when the doping content was 0.4 at.%, with better piezoelectric response. Also, the reason improving piezoelectric properties was further analyzed by impedance spectra. The findings indicate that constructing such defect pairs can efficiently improve the piezoelectric properties of relaxed ferroelectrics.

Formation of White Etching Layers by Deep Rolling of AISI 4140 Steel

Deep rolling is an effective mechanical surface treatment method; however, the induced deformation may eventually lead to changes that result in a structure known as a white etching layer (WEL). The WEL possesses a distinct constitution and properties compared with the surrounding bulk material. The presence of the WEL drastically affects the surface integrity of the part and impairs the performance of the metallic components. However, the influence of deep rolling on WEL formation has not been fully clarified. Therefore, the goal of this study was to investigate WEL formation after deep rolling AISI 4140 steel with various microstructures (obtained through four heat treatment routes) and employing distinct rolling pressure and feed values. The results show that larger lattice distortion (resulting from refined martensitic structures) and higher deep rolling feed (increased work hardening) lead to the formation of a thicker WEL. Moreover, the increase in rolling pressure does not affect the WEL within the tested range. Finally, the mechanisms involved in WEL formation are discussed. It is suggested that the shear energy associated with deep rolling and applied along the surface grains leads to WEL formation by grain refinement.

Mechanisms for improving tensile properties at elevated temperature in fire-resistant steel with Mo and Nb

Fire resistance of structural steels used in buildings is typically evaluated based on the ratio of the yield strength at 600 °C to that at room temperature. Fire-resistant steel shows a yield strength ratio of more than 2:3 between 600 °C and room temperature and achieves an excellent high-temperature strength. Alloying elements such as Mo and Nb are used to improve the strength at elevated temperatures. In this study, the effects of the addition of Mo and Nb on the fire resistance of steel were carefully investigated using SEM, TEM, in-situ TEM, EPMA, 3D-APT, positron annihilation lifetime spectroscopy, and first principles calculations. The fire resistance in Mo and Nb added steel (Mo + Nb) was shown to be drastically improved compared to plain carbon steel (CMn). The improvement in the high-temperature strength in Mo + Nb was attributed to the precipitation of fine Nb-rich MX particles and a solid solution of Mo and Nb hindering the dislocation movement, and thereby minimizing the dislocation annihilation at elevated temperature. The solid solution of Mo and Nb lowers the vacancy formation energy and allows a vacancy to form more easily, leading to a large lattice distortion which results in a slower dislocation mobility in Mo + Nb.

Improved ferromagnetism and magnetodielectric properties of relaxor ferroelectric Ba4-Ca Nd2Fe1.5Co0.5Nb8O30 ceramics with tungsten bronze structure

Abstract The structural, magnetic, dielectric and magneto-dielectric properties of tungsten bronze Ba4-xCaxNd2Fe1.5Co0.5Nb8O30 (0 ≤ x ≤ 0.9) were investigated. All the samples can be indexed with the tetragonal structure and the space group of P4bm. The incorporation of Ca ions improves the structural distortion and promotes the grain’s growth. The magnetic curves at 300 K indicate the superposition of ferromagnetic (FM) and antiferomagnetic (AFM) state in all the samples, the observed FM phase can be attributed to the spin canting of AFM coupling of Fe- and Co-based sublattices. The Ca-doped samples exhibit an improved FM state due to large lattice distortion. The dielectric constant in anomaly region obeys well with Curie-Weiss law with γ = ∼1.6, implying that all the samples are relaxor ferroelectrics. The dielectric loss relaxations obey with Vogel-Fulcher relation and can be ascribed to the local polarization fluctuation induced by chemical heterogeneities. In addition, the relative change in magnetic field dependent dielectric constant follows with the change in the square of magnetization M2, suggesting that the observed magneto-dielectric is caused by the intrinsic magnetoelectric (ME) coupling effect. These results manifest that tungsten bronze compounds may be the potential candidates for the application in ME devices.

Electron-lattice interplay in LaMnO3 from canonical Jahn-Teller distortion notations

LaMnO$_3$ is considered as a prototypical Jahn-Teller perovskite compound, exhibiting a metal to insulator transition at $T_{JT} = 750K$ related to the joint appearance of an electronic orbital ordering and a large lattice Jahn-Teller distortion. From first-principles, we revisit the behavior of LaMnO$_3$ and show that it is not only prone to orbital ordering but also to charge ordering. Both charge and orbital orderings appear to be enabled by rotations of the oxygen octahedra and the subtle competition between them is monitored by a large tetragonal compressive strain, that is itself a Jahn-Teller active distortion. Equally, the competition of ferromagnetic and antiferromagnetic orders is slave of the same tetragonal strain. Our results further indicate that the metal to insulator transition can be thought as a Peierls transition that is enabled by spin symmetry breaking. Therefore, dynamical spin fluctuations in the paramagnetic state stabilize the insulating phase by the instantaneous symmetry breaking they produce and which is properly captured from static DFT calculations. As a basis to our discussion, we introduce canonical notations for lattice distortions in perovskites that distort the oxygen octhedra and are connected to charge and orbital orderings.

The effect of phase on microstructure and mechanical performance in TiAlN and TiSiN films

To study the effect of phase on the microstructure and mechanical properties of nitride coatings, three films of TiN, TiAlN, and TiSiN were prepared on the surface of high-speed steel using hollow cathode assisted multi-arc ion plating technique. The XRD lines of the three films were analyzed and calculated by linear analysis. The element and phase of the film were observed and analyzed by x-ray Diffraction (XRD), Transmission Electron Microscope (TEM), energy dispersive x-ray analysis (EDS). The microstructure and film thickness of the coating were characterized by scanning electron microscopy (SEM). The surface roughness of the film was observed by Confocal laser scanning microscope (CLSM). The hardness, friction coefficient, and coating/substrate adhesion of the film were tested by the G200 nanometer hardness tester and CETR UNMT-1 surface micro-nano mechanical test system. We discovered two different reinforcement mechanisms. The high microscopic strain value (1.309 × 10−3) in the TiAlN film was related to the formation of Ti3AlN substitutional solid solution in the film formed a large lattice distortion,however, the coating/substrate adhesion (33.5 N) was lowered. The result of independent nucleation and growth of the Si3N4 phase in the TiSiN film refines the structure of the film, alleviating the increase of microscopic strain. At this time, the coating/substrate adhesion reaches the highest value of 40 N and the film surface roughness reaches the minimum value of 0.451 μm. The results also show that the TiSiN coating can obtain good coating/substrate adhesion without pre-plating.

ZnO transparent conducting thin films codoped with anions and cations

In the past two decades, ZnO related materials and devices are widely used for various applications, such as thin-film transistors, photodetectors, light-emitting diodes, and transparent conductors because ZnO has several appealing features like abundant raw materials, environmental friendliness, wide and direct band gap, high electron mobility, and large exciton bonding energy. Especially, ZnO has been recognized as one of the most promising candidates for substituting commercial transparent conductors ITO which is exploited as transparent electrodes in solar cells and flat planar display and transparent heaters etc. For example, aluminum doped ZnO (AZO) transparent conducting films have been commercialized successfully. However, the figure of merits and stability of ZnO transparent conducting films still need to be further improved in order to meet the strict demands of practical large-scale applications. So far, various techniques have been developed to alleviate that contradiction between conductivity and visible light transmittance. In the past few years, a new strategy called anion and cation co-doping in ZnO has been widely implemented to improve the figure of merit, in which IIIA group elements are used as cation dopants and fluorine is used as anion dopants. It is worth noting that F has several advantages as anion dopant in ZnO. First, fluorine has a similar ionic radius with oxygen, which will avoid large lattice distortion. Second, the substitution for oxygen with fluorine only disturbs the valence band of ZnO and leaves the conduction band unaffected, which is beneficial for achieving high electron mobility. In this review, the latest researches of F and boron, or aluminum, or gallium, or indium co-doped ZnO thin films are summarized from both the theoretical and the experimental aspects. Effects of anion and cation co-doping on the optical and electrical properties and thermal stability of ZnO thin films are systematically discussed. Both theoretical and experimental results show that cation and anion co-doping can effectively improve the conductivity and visible light transmittance, no matter ZnO thin films were prepared by physical vapor deposition or synthesized by chemical solution processs. Taking Al and F co-doped ZnO (AFZO) thin films prepared with pulse laser deposition as an example, the mobility of AFZO thin film was apparently higher than that of Al-doped ZnO at the same carrier concentration. The high carrier mobility of AFZO is due to that the F can passivate the surface defects and acceptor-like complex defects in ZnO. In addition, the highly electronegative F makes the AFZO thin films exhibit excellent thermal stability, e.g. maintaining high conductive even after air-annealing at 600°C. These results indicate that anion and cation co-doping can effectively improve the performance of ZnO transparent conductive thin films and broaden their applications. Despite these exciting achievements, challenges still remain in the field of anion and cation co-doped ZnO thin films. For example, the mechanism of the co-doping strategy has not been clarified because the formation energy of intrinsic defects in ZnO is relatively low and the defects configurations for anion and cation co-doping are more complicated than single element doping case. Besides, we are still short of effective techniques and theoretical methods to reveal and simulate the behavior of defect clusters in co-doped ZnO. It is also urgent to establish the industrial standard of ceramic targets for co-doped ZnO to eliminate the discrepancies between different groups. More efforts should also be made in developing new equipment for large-scale manufacturing co-doped ZnO thin films. We hope this paper will provide reference to the readers who are interested in transparent conducting oxides.

Fundamental electronic structure and multiatomic bonding in 13 biocompatible high-entropy alloys

High-entropy alloys (HEAs) have attracted great attention due to their many unique properties and potential applications. The nature of interatomic interactions in this unique class of complex multicomponent alloys is not fully developed or understood. We report a theoretical modeling technique to enable in-depth analysis of their electronic structures and interatomic bonding, and predict HEA properties based on the use of the quantum mechanical metrics, the total bond order density (TBOD) and the partial bond order density (PBOD). Application to 13 biocompatible multicomponent HEAs yields many new and insightful results, including the inadequacy of using the valence electron count, quantification of large lattice distortion, validation of mechanical properties with experiment data, modeling porosity to reduce Young’s modulus. This work outlines a road map for the rational design of HEAs for biomedical applications.

Electronic nematicity in Sr2RuO4

We have measured the angle-resolved transverse resistivity (ARTR), a sensitive indicator of electronic anisotropy, in high-quality thin films of the unconventional superconductor Sr2RuO4 grown on various substrates. The ARTR signal, heralding the electronic nematicity or a large nematic susceptibility, is present and substantial already at room temperature and grows by an order of magnitude upon cooling down to 4 K. In Sr2RuO4 films deposited on tetragonal substrates the highest-conductivity direction does not coincide with any crystallographic axis. In films deposited on orthorhombic substrates it tends to align with the shorter axis; however, the magnitude of the anisotropy stays the same despite the large lattice distortion. These are strong indications of actual or incipient electronic nematicity in Sr2RuO4.

Effect of Dy doping on magnetostrictive and mechanical properties of Fe83Ga17 alloy

Fe83Ga17 alloy is a kind of promising magnetostrictive alloys with high magnetostrictive properties and a low saturation magnetic field. As-cast Fe83Ga17Dyx (x=0, 0.05, 0.1, 0.2, 0.4) polycrystalline alloys were prepared by arc melting. Effect of Dy doping on the microstructure, magnetostrictive and mechanical properties of as-cast Fe83Ga17 alloy was investigated. Results show that Dy-doped alloys exhibit a dual-phase structure containing the A2 matrix and Dy-rich precipitates (Fe56Ga34Dy10). Both magnetostriction and mechanical properties of Fe83Ga17 alloys are improved by Dy doping. A small amount of Dy addition (x=0.2) significantly causes Fe83Ga17 alloy to transform from typical brittle material (fracture strain ε<1%) to plastic material (ε≈11%). Correspondingly, the fracture mode transforms from intergranular fracture to dimple fracture. At the same time, the ultimate tensile strength and the magnetostriction rise up to 209 MPa and 64 ppm, respectively. Dy-rich precipitates disperse along the grain boundries and inside the grains, which plays an important role in the grain refinement and solution strengthening, and therefore, contribute to the enhancement of mechanical properties of the alloy. The improvement of magnetostriction could be attributed to the large lattice distortion induced by Dy atoms entering into the A2 matrix. Doping Dy into Fe-Ga alloys provides an effective solution to the brittleness in their applications.

Achieving a High-Strength CoCrFeNiCu High-Entropy Alloy with an Ultrafine-Grained Structure via Friction Stir Processing

High-entropy alloys (HEAs) are a new class of materials with a potential engineering application, but how to obtain ultrafine or nano-sized crystal structures of HEAs has been a challenge. Here, we first presented an equiatomic CoCrFeNiCu HEA with excellent mechanical properties obtained via friction stir processing (FSP). After FSP, the Cu element segregation in the cast CoCrFeNiCu HEA was almost eliminated, and the cast coarse two-phase structure (several micrometers) was changed into an ultrafine-grained single-phase structure (150 nm) with a large fraction of high-angle grain boundaries and nanoscale deformation twins. This unique microstructure was mainly attributed to the severe plastic deformation during FSP, and the sluggish diffusion effect in dynamics and the lattice distortion effect in crystallography for HEAs. Furthermore, FSP largely improved the hardness and yield strength of the CoCrFeNiCu HEA with a value of 380 HV and more than 1150 MPa, respectively, which were > 1.5 times higher than those of the base material. The great strengthening after FSP was mainly attributed to the significant grain refinement with large lattice distortion and nano-twins. This study provides a new method to largely refine the microstructure and improve the strength of cast CoCrFeNiCu HEAs.

Basal shearing of twinned stacking faults and its effect on mechanical properties in an Mg–Zn–Y alloy with LPSO phase

The precipitates inside deformation twins may block the dislocation motion and consequently affect the mechanical property of materials. Herein, at the atomic level, we directly visualize that the basal dislocation slips shear the twinned stacking faults (TSFs) within the deformation twins in an Mg–Zn–Y alloy containing long-period stacking ordered (LPSO) structures. The TSFs, enriched with solute atoms, could be considered as precipitates inside deformation twins. They are sheared by a single step or multiple shearing steps on the basal plane. The microstructural fingerprints, i.e., the width of basal shearing steps, enable a quantitative assessment of the local and total plastic shear strain due to the basal dislocation within the deformation twins. The TSFs can block dislocation slip, while the dislocation shearing induces large lattice distortion and even solute atoms redistribution at local intersection. The TSFs-dislocation interaction is expected to lower the basal dislocation motion and resultantly modulate the mechanical properties of magnesium alloys. These results may offer a novel strategy for strengthening and toughening magnesium alloys via tailoring the shearable precipitates.

High‐Performance Manganese Hexacyanoferrate with Cubic Structure as Superior Cathode Material for Sodium‐Ion Batteries

AbstractSodium manganese hexacyanoferrate (NaxMnFe(CN)6) is one of the most promising cathode materials for sodium‐ion batteries (SIBs) due to the high voltage and low cost. However, its cycling performance is limited by the multiple phase transitions during Na+ insertion/extraction. In this work, a facile strategy is developed to synthesize cubic and monoclinic structured NaxMnFe(CN)6, and their structure evolutions are investigated through in situ X‐ray diffraction (XRD), ex situ Raman, and X‐ray photoelectron spectroscopy (XPS) characterizations. It is revealed that the monoclinic phase undergoes undesirable multiple two‐phase reactions (monoclinic ↔ cubic ↔ tetragonal) due to the large lattice distortions caused by the Jahn–Teller effects of Mn3+, resulting in poor cycling performances with 38% capacity retention. The cubic NaxMnFe(CN)6 with high structural symmetry maintains the structural stability during the repeated Na+ insertion/extraction process, demonstrating impressive electrochemical performances with specific capacity of ≈120 mAh g−1 at 3.5 V (vs Na/Na+), capacity retention of ≈70% over 500 cycles at 200 mA g−1. In addition, the TiO2//C‐MnHCF full battery is fabricated with an energy density of 111 Wh kg−1, suggesting the great potential of cubic NaxMnFe(CN)6 for practical energy storage applications.

Cone-spiral magnetic ordering dominated lattice distortion and giant negative thermal expansion in Fe-doped MnNiGe compounds

By utilizing the large lattice distortion caused by incommensurate cone-spiral magnetic ordering and the induced texture effect in Fe-doped MnNiGe alloys, NTE largely exceeding the average crystallographical contribution has been achieved.

A Highly Enhanced Photoluminescence of Eu3+-Activated CaTiO3 Phosphors via Selective A-Site and B-Site Cation Substitutions (Sr2+ and Sn4+)

Sr2+ and Sn4+ doped CaTiO3:Eu3+ phosphors were prepared by a high temperature solid-state method. X-ray diffraction characterization shows that the sample calcined at 1200°C is pure and has an orthorhombic crystal lattice. Photoluminescence (PL) measurement shows that CaTiO3:Eu3+ has five excitation peaks at 363 nm, 381 nm, 398 nm, 418 nm, and 466 nm, respectively corresponding to the transitions 7F0 → 5D4, 7F0 → 5L7, 7F0 → 5L6, 7F0 → 5D3 and 7F0 → 5D2 of Eu3+. The main emission peaks of CaTiO3:Eu3+ at 592 nm and 613 nm are ascribed to the 5D0 → 7FJ (J = 1, 2) transitions of Eu3+. In addition, PL emissions at 592 nm and 613 nm of CaTiO3:Eu3+ phosphors are enhanced remarkably through A-site substitution of Ca2+ with Sr2+ or B-site substitution of Ti4+ with Sn4+. Noticeably, the emission intensity of Ca(Ti,Sn)O3:Eu3+ is nearly three times higher than that of CaTiO3:Eu3+. The reason is that substitution of Ti4+ with Sn4+ induces a large lattice distortion, which promotes the 5D0 → 7F2 transition probability and thus enhances the emissions at 613 nm. It is also found that Sr2+ substitution narrows the optical bandgaps of CaTiO3:Eu3+ , while Sn4+ substitution widens them. In addition, chromatic purity of the phosphors shows a remarkable dependence on the asymmetric ratio.

Magnetic, Structural, and Optical Properties of Gadolinium-Substituted Co0.5Ni0.5Fe2O4 Spinel Ferrite Nanostructures

Gadolinium-substituted cobalt–nickel ferrite Co0.5Ni0.5GdxFe2-xO4 (0 ≤ x ≤ 1.0) nanostructures have been synthesized by hydrothermal approach which results more hydrophilic surface properties important for biomedical applications. Structural analysis by X-ray diffraction revealed the formation of a single-phase spinel ferrite for all samples and crystallite size is ranging from 13 to 28 nm. Lattice constant decreases with increasing Gd3+ ion concentration due to differences between ionic radii of Gd3+ and Fe3+. Morphological analysis by scanning and transmission electron microscopy indicated the shape transformed from agglomerated particles into rod-shaped with increasing Gd content. Fourier transform infrared analysis also correlated the presence of the spinel ferrite structure. Optical band gap measurement implied that band gap decreases with increasing Gd content. In order to determine magnetic properties of cobalt–nickel spinel ferrite nanostructures, isothermal magnetization measurements have been obtained at 300 and 15 K using vibrating sample magnetometer. Magnetic properties are strongly depending on Gd substitution ratio, which alters the crystallite size, cation distribution, and exchange interactions between octahedral and tetrahedral sites of nanostructures. Saturation magnetizations decreased with increasing Gd substitution at both temperatures since cation distribution at different sites and large lattice distortion caused by Gd3+ ion substitution. Due to complex relations between the shape anisotropy, crystallite size, grain boundaries, secondary phases, and increasing Gd content observed in Co0.5Ni0.5GdxFe2-xO4 nanostructures, coercivity results in different magnetocrystalline anisotropy behavior.

Mn‐promoting formation of a long‐period stacking‐ordered phase in laser‐melted Mg alloys to enhance degradation resistance

AbstractMagnesium (Mg) alloys are promising candidates for use as biomedical implant materials. However, their very fast degradation rate greatly restricts their application. A rare earth phase possessed with a long‐period stacking‐ordered (LPSO) structure was in favor of enhancing the degradation resistance of Mg alloys. In fact, the formation of the LPSO phase in Mg alloys depends on their stacking fault energy. The lower the stacking fault energy, the more the LPSO phase formed. In this study, manganese (Mn) was alloyed to Mg alloy ZK30–10Gd (containing 3 wt.% Zn and 10 wt.% Gd) via selective laser melting to promote the formation of the LPSO phase. As an alloying element, Mn could be in favor of reducing stacking fault energy due to the fact that the large difference between the atomic radius of Mn and that of Mg induced large lattice distortion to facilitate forming stacking faults. The results showed that as the Mn content increased from 0 to 1.2 wt.%, the area fraction of LPSO phase increased from 12.22% to 22.37%, meanwhile the area fraction of (Mg,Zn)3Gd phase decreased from 9.31% to 2.32%. The ZK30–10Gd–0.6Mn possessed the highest degradation resistance (weight loss rate 0.38 mg · cm−2 · day−1). The enhancement of degradation resistance had two reasons. On the one hand, more LPSO phase provided more sites for nucleation of degradation products, which could promote the formation of a homogeneous and compact degradation product film to protect the Mg matrix. On the other hand, the inhibition of (Mg,Zn)3Gd phase precipitation could reduce galvanic corrosion.

High energy storage density achieved in Bi3+-Li+ co-doped SrTi0.99Mn0.01O3 thin film via ionic pair doping-engineering

The demand for lead-free dielectric capacitors with rapid charge-discharge ability and high energy storage density is increasing owing to the rapid development of electronic equipment. Lead-free Sr1-x(Bi0.5Li0.5)xTi0.99Mn0.01O3 (x = 0.02, 0.025, 0.03, 0.035) thin films grown on Pt/Ti/SiO2/Si substrates were prepared by sol-gel method. A huge enhancement in polarization was found in Bi3+-Li+ co-doped SrTiO3 thin films. The large lattice distortion and local broken-symmetry due to formation of Bi3+-Li+ ionic pairs are responsible for ferroelectricity and high polarization. The maximum polarization (42.1 μC/cm2) and largest energy storage density of 47.7 J/cm3 at 3307 kV/cm were both achieved in Sr0.975(Bi0.5Li0.5)0.025Ti0.99Mn0.01O3 thin film. Moreover, an excellent temperature-dependent stability was also obtained in Sr0.975(Bi0.5Li0.5)0.025Ti0.99Mn0.01O3 thin film from 30 to 110 °C.

Destabilizing the Dehydrogenation Thermodynamics of Magnesium Hydride by Utilizing the Immiscibility of Mn with Mg.

Hydrogen storage is a key technology for the advancement of hydrogen and fuel cell power technologies in stationary and portable applications. MgH2, an example of a high-capacity hydrogen storage material, has two major material challenges for practical applications: slow hydrogen desorption kinetics and high hydrogen desorption temperature. Numerous studies have reported enhancements in kinetics but only a few in thermodynamics. Here, we present a simple but effective way to improve upon both the kinetic and thermodynamic aspects of desorption by utilizing the immiscibility of Mn, a non-hydrogen absorbing metal, with Mg. Mg0.25Mn0.75, prepared through ball milling MgH2 and Mn powders, is a nanocomposite where the nanometer-sized MgH2 domains are randomly embedded in a Mn matrix. This sample readily and reversibly absorbs and desorbs deuterium even at a temperature of 200 °C without the addition of any catalysts. This is nearly 180 °C lower than the typical operating temperature of conventional bulk Mg. Furthermore, at a given temperature, its deuterium desorption pressure is clearly elevated compared to that of pure Mg, indicating the destabilization of MgD2. The average crystallite size of MgD2 in deuterated Mg0.25Mn0.75 determined from X-ray diffraction data is around 9 nm. Nuclear magnetic resonance spectroscopy studies show that MgD2 domains are heavily strained and some of the D atoms are coordinated by a few Mn atoms, suggesting that a large number of lattice defects, including the partial substitution of Mg with Mn, are introduced during ball milling. Furthermore, the Mn matrix firmly locks nanosized MgD2, preventing the agglomeration of MgD2 below 250 °C. Our study suggests that a synergistic effect created by nanosizing, large lattice distortions, and robust interfaces between MgD2 and the Mn matrix can effectively and concurrently improve the kinetics and thermodynamics of MgD2 in Mg0.25Mn0.75. Our work demonstrates the possibility of utilizing the immiscibility of metals with Mg to synthesize a robust nanostructure that can alter the kinetics and stability of MgH2.