Solid Solution Behavior Research Articles

Thermodynamics and kinetics of long-range ordering in FCC Ni–33at.%Cr alloys: Insights from atomic scale modeling

This study investigates the thermodynamics and kinetics of the NiCr system, focusing specifically on the kinetics of the order–disorder phase transformation in the Ni–33at.%Cr alloy. Combining density functional theory, CALPHAD-type models, and experimental diffusion data, we introduce and validate an efficient pair interaction model (PIM) and use it in Monte Carlo simulations. Our results include a detailed phase diagram of NiCr in face-centered cubic structure and kinetic models that delineate the behavior of solid solutions at high temperatures and ordered structures at low temperatures. The simulations shed light on tracer diffusion and ordering kinetics within Ni–33at.%Cr, demonstrating good agreement with existing experimental data. Furthermore, our simulation-driven insights prompt a reevaluation of certain aspects of related experimental studies concerning the apparent ordering activation enthalpies and growth kinetics. We also provide a thorough discussion on the strengths of our models and features for future improvement.

Unlocking the charge efficiency of γ’-V2O5 for Na-ion battery through a solution synthesis technique

In this study, the γ’-V2O5 cathode material was prepared through a solution synthesis technique leading to homogeneous, fine and porous particles 100–200 nm in size. This successful preparation allows to overcome the huge drawback of the microsized material in terms of charge efficiency and to take benefit of the attractive Na insertion properties of γ’-V2O5, i. e. a significant available capacity of 145 mAh g- 1, a high working potential of about 3.25 V vs. Na+/Na, an excellent charge efficiency, a high-rate capability and good cycle life. A detailed structural study upon Na insertion/extraction shows that the proposed nanosizing approach promotes a homogeneous Na solubility and solid solution behavior in a wider composition range (0.4 < x ≤ 1 in γ-NaxV2O5) compared to the results previously reported for solid-state synthesized γ’-V2O5. Furthermore, highly reversible structural changes are evidenced. Key kinetic parameters governing the Na insertion-extraction reaction are discussed thanks to an impedance spectroscopy study revealing a faster Na diffusivity in the one-phase region. The obtained results allow a comprehensive understanding of the enhanced performance exhibited by the present sub-micronic γ’-V2O5 material.

Crystal structure evolution and solid solution mechanism of Al2O3-Cr2O3 system under different reaction conditions

The (Al1-xCrx)2O3 solid solution (ACS) is expected to be an low pollution chromium source for high-performance alumina-chromium oxide refractory materials. In this work, the effects of Cr2O3 content and reaction conditions on the solid solution behavior in the Al2O3-Cr2O3 system were explored and the mechanism was revealed. The relationship between the lattice parameters of the formed ACS phase and the content of Cr2O3 was closer to a linear one as the temperature rose, serving as an indicator for a higher degree of reaction. The solid solution reaction between Al2O3 and Cr2O3 was governed by the diffusion processes of Al3+ and Cr3+ at 1300–1500 °C and 1200 °C, respectively, and thus the increase of Cr2O3 content slowed the solid solution reaction at a low temperature whereas promoted it at elevated temperatures. The diffusion process of solid solution reaction within the Al2O3-Cr2O3 system was consistent with the Cater model; The diffusion activation energy (Ea) decreased as the content of Cr2O3 increased at 1300–1500 °C. When the content of Cr2O3 increased from 25 to 60 mol%, the diffusion activation energy decreased from 92.48 to 86.49 kJ/mol−1, which was attributed to the augmentation in the diffusion rate of Cr3+ caused by the increase of Cr2O3 content and its vapor-phase transport mechanism at high temperatures.

Evolution of inclusions in DH36 grade ship plate steel during high heat input welding

In this paper, the solid solution and precipitation behavior of inclusions on the surface and 1/2 thickness of the tested steel plate under the condition of welding heat input of 400 kJ/cm is investigated by using laser confocal experiments with hot-rolled state DH36 ship plate steel as the research object, and the mechanism of the effect of inclusions on the phase transformation of an acicular ferrite is revealed. The results show that the inclusions of the tested steel are mainly composed of Oxide-MnS, MnS, Oxide, TiN, Spinel, etc. The amount of inclusions on the surface of the tested steel plate is significantly higher than that at the 1/2 thickness position. During the heating stage, the small inclusions on the surface immediately disappeared, and the large inclusions gradually solidified in the matrix; atomic diffusion occurred at the bond between the inclusions and the matrix; while the small inclusions at the 1/2 thickness position gradually disappeared at the beginning of the heating stage, and the inclusions began to precipitate and grow when the temperature was increased to 990 °C. The acicular ferrite preferentially nucleates and grows near the boundary of the inclusions during the post-weld cooling stage, and its growth ends when two acicular ferrites cross.

Structure, Thermodynamics, Chemomechanics, and Kinetics: The Hidden Complexities of LiNiO2

After being abandoned due to mechanical and thermodynamic instabilities, layered transition metal oxides with ultra-high Ni content currently see a revival as promising cathode active material in the effort of further pushing the energy density of lithium ion batteries. Because such materials are in many aspects closely related to the pure LiNiO2, understanding the properties and mechanisms of this model system on an atomic level is vital for the development of more complex materials. Therefore, we have analyzed the structure, thermodynamics, chemomechanics and kinetics of LiNiO2 and its delithiated states including the presence of native defects by making use of atomistic simulations to grasp the peculiarities of this material.What makes the structure and related properties of LiNiO2 especially interesting and challenging is the presence of dynamic Jahn-Teller distortions of the NiO6 octahedra. This leads to local monoclinic distortions and our simulations revealed why the material still appears to be of rhombohedral symmetry on a global scale.[1]Upon delithiation and the concurrent oxidation to Ni4+, the Jahn-Teller distortions start to vanish and particularly stable Li orderings may be observed. In this context, we used a cluster expansion approach and were able to reproduce the experimental phase diagram. Moreover, we included native defects in the analysis because LiNiO2 can hardly be prepared stoichiometric. Instead, many synthesis approaches lead to additional Ni ions occupying the Li layers (NiLi). The introduction of such defects as well as other substitutionals in a surrogate model shows that single phase regions tend to be suppressed and solid-solution behavior is favored. This smooths the voltage curves and gives good agreement with experiments.[2]We then focused on more extended defects in layered transition metal oxides: Stacking faults (observed at low Li content and responsible for stacking changes from O3 to O1-type layering) and dislocations (needed to drive stacking changes through the material). We found that the energetics and gliding barriers of stacking faults in stoichiometric LiNiO2 are similar to LiCoO2 for all degrees of lithiation. However, by acknowledging the presence of NiLi we quantified for the first time how this defect hinders layer gliding: In the fully delithiated material, 2% of NiLi in the Li layer has a similar effect as 11%-15% Li, effectively increasing the gliding barriers. In terms of dislocations, their excess energies in LiNiO2 are much lower than in LiCoO2, which we mostly attribute to the Jahn-Teller distortions that are able to collinearly orient in the vicinity of a dislocation in LiNiO2, effectively taking a part of the strain. Moreover, dislocations are able to attract both Li and O vacancies, potentially affecting the kinetics of the material as well as acting as a precursor for further degradation mechanisms.[3]Lastly, we mention our recent analysis again focusing on NiLi defects. Our simulations show that such Ni ions remain in a +2 oxidation state independent on the degree of lithiation. This contradicts the broad opinion of an oxidation state change to +3 at low Li content, which is believed to lead to a local constriction of the layer that can hardly be relithiated again. Nevertheless, we show that NiLi indeed leads to an attraction of Li vacancies within two lattice sites and the potential to split fast divacancies into two considerably slower single vacancies. These observations together with the fact that any NiLi depicts an obstacle for diffusing Li ions or Li vacancies shed light on the kinetics of non-stoichiometric LiNiO2 and support the development of further optimization schemes.[4][1] Chem. Mater. 2020, 32, 23, 10096–10103[2] J. Mater. Chem. A , 2021,9, 14928-14940[3] Chem. Mater. 2023, 35, 2, 584–594[4] https://doi.org/10.26434/chemrxiv-2023-hkmsn-v3

A first step towards understanding thermomechanical behavior of the Nb-Cr system through interatomic potential development and molecular dynamics simulations

Utilizing a preliminary interatomic potential, this work represents an initial exploration into the thermomechanical behavior of NbCr solid solutions. Specifically, it examines the effect of different amounts of Cr solute, for which information in the literature is limited. The employed interatomic potential was developed according to the embedded atom model (EAM), and was trained on data derived from density functional theory calculations. While the potential demonstrated reasonable accuracy and predictive power when tested, various results highlight deficiencies and encourage further development and training. Mechanical strength, heat capacities, thermal expansion coefficients, and thermal conductivities were found to decrease with Cr content. Elastic coefficients, too, were observed to be strongly dependent on Cr composition. The Pugh embrittlement criterion was not satisfied for any of the compositions and temperatures explored. Gibbs free energy calculations performed on C14, C15, and C36 NbCr2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document} allotropes predicted the C36 structure to be the most thermodynamically favorable across all investigated temperatures and it was found that C36 becomes increasingly more stable relative to the other two phases with increased pressure. The inability of this work to accurately capture the stability of the different Laves phases is most likely due to the shortcomings in the developed potential.

Unlocking highly reversible V5+/V4+ redox reaction and fast-stable Na storage in NASICON cathodes by electronic structure optimization and solid-solution behavior regulation

It is formidable to fully exert NASICON-structured Na3V2(PO4)3's (NVP) energy density due to the serious structural degradation aroused from the undesirable phase evolution and transition metal ion migration upon high potential versus Na+/Na. To break through the energy limitation of NVP, we meticulously selected three classes of metal elements to employ a novel quaternary substitution in NVP. Theoretical calculation expresses that their 3p, 3d, 4 f orbits hybrid synergy can favor the electron rearrangement signally, increasing the accessibility of the V5+/V4+ redox reaction. Therefore, Na3V1.6(CrAlFeCe)0.1(PO4)3 (NVMP) cathode delivers a groundbreaking energy density of 420 Wh kg−1. Besides, the solid-solution mechanism of Na storage during the V5+/V4+ reaction process was validated by ex situ XRD, demonstrating the significant effect of quaternary substitution on inhibiting irreversible phase evolution under high charge states. Hence, NVMP can maintain the activated V5+/V4+ after 10000 cycles. The fast Na-storing kinetics of NVMP were analyzed by in situ EIS, in situ DRT, GITT, and various scan rate CV. This work provides new insights for adjusting electronic structure and Na storing behavior in NASICON cathodes.

Mitigating Sodium Ordering for Enhanced Solid Solution Behavior in Layered NaNiO2 Cathodes.

The O-type layered nickel oxides suffer from undesired cooperative Jahn-Teller distortion stemming from Ni3+ ions and undergo multiple biphasic structural transformations during the insertion/extraction of large Na+ ions, posing a significant challenge to stabilize the structural integrity. We present here a systematic investigation of the impact of substituting 5 % divalent (Mg2+) or trivalent (Al3+ or Co3+) ions for Ni3+ to alleviate Na+ion ordering and perturb the Jahn-Teller effect to enhance structural stability. We gauge a fundamental understanding of the Mg-O and Na-O or Mg-O-Na bonding interactions, noting that the ionicity of the Mg-O bond deshields the electronic cloud of oxygen from Na+ ions. Furthermore, calculations of the Van Vleck distortion modes reveal a relaxation of NiO6 octahedra from Jahn-Teller distortion and a reduced electron density at the interlayer with Mg2+ substitution. Long-range (operando X-ray diffraction) and short-range (magic angle spinning nuclear magnetic resonance) structural analyses provide insights into reduced ordering, allowing a stable continuous solid solution. Overall, Mg-substitution results in a high-capacity retention of ~96 % even after 100 cycles, showcasing the potential of this strategy for overcoming the structural instabilities and enhancing the performance of sodium-ion batteries.

Mitigating Sodium Ordering for Enhanced Solid Solution Behavior in Layered NaNiO2 Cathodes

AbstractThe O‐type layered nickel oxides suffer from undesired cooperative Jahn–Teller distortion stemming from Ni3+ ions and undergo multiple biphasic structural transformations during the insertion/extraction of large Na+ ions, posing a significant challenge to stabilize the structural integrity. We present here a systematic investigation of the impact of substituting 5 % divalent (Mg2+) or trivalent (Al3+ or Co3+) ions for Ni3+ to alleviate Na+ion ordering and perturb the Jahn–Teller effect to enhance structural stability. We gauge a fundamental understanding of the Mg−O and Na−O or Mg−O−Na bonding interactions, noting that the ionicity of the Mg−O bond deshields the electronic cloud of oxygen from Na+ ions. Furthermore, calculations of the Van Vleck distortion modes reveal a relaxation of NiO6 octahedra from Jahn–Teller distortion and a reduced electron density at the interlayer with Mg2+ substitution. Long‐range (operandoX‐ray diffraction) and short‐range (magic angle spinning nuclear magnetic resonance) structural analyses provide insights into reduced ordering, allowing a stable continuous solid solution. Overall, Mg‐substitution results in a high‐capacity retention of ~96 % even after 100 cycles, showcasing the potential of this strategy for overcoming the structural instabilities and enhancing the performance of sodium‐ion batteries.

Investigating magnetic, and magneto-electric properties of Nd doped [(1-y) Bi1-xNdxFeO3-yPbTiO3] solid solution

Magneto-electronic devices applications of room-temperature multiferroics have been made possible by recent developments. But the potential use of pure BFO in multifunctional devices is constrained by its antiferromagnetic nature and need substitution-induced modification to improve magnetic and magnetoelectric properties. In the present paper, attempt has been made to improve the magnetic and magnetoelectric properties of the BiFeO3-PbTiO3 solid solution by incorporating Bismuth cation with Lead(II) ion and Ferric cation with Titanium cation into the formulation of Nd doped,(1-y)Bi1-xNdxFeO3-yPbTiO3where x = 0.05,0.10,0.15,0.20 and y = 0.1, 0.2,0.3 and 0.4. The impact of different PbTiO3 and Nd compositions on magnetoelectric and magnetic characteristics of solid solution has been investigated. The results showed that, degree of magnetization continuously increases with increasing Nd doping by affecting Fe-O-Fe angles. However, the magnetization drops as the volume of PbTiO3 rises, that may be attributed to a rise in the tetragonal phase of solid solutions. The improvement of the magnetoelectric coupling coefficient and change of antiferromagnetic behaviour to ferromagnetic behaviour of solid solutions has been observed with increasing Nd doping. This enhance the ferromagnetic behaviour of the compound.

Effect of Oxygen in Mo-TM (TM = Ti, Zr, Hf) Solid Solutions as Studied with Density Functional Theory Calculations

Mo-Ti-Si, Mo-Zr-B, and Mo-Hf-B are promising alloy systems for high-temperature applications as they show higher toughness and higher creep resistance than other Mo-based alloys. Regarding ductility and toughness, the chemical composition of the Mo solid-solution phase is the main parameter with which to tweak these properties of multiphase Mo-based alloys. Besides the common solid-solution hardening, one goal is to minimize embrittlement by decreasing the detrimental effects of interstitials like oxygen atoms in Mo alloys, which might be present in the bulk material due to trapping. For a better understanding of the trapping mechanisms and behavior of Mo solid solutions, the bonding situation and interaction of Mo atoms with the atoms of the alloying partners, as well as oxygen atoms, is worthwhile to investigate. For this, an in-depth analysis of the chemical bonding situation with calculations based on density functional theory in selected Mo-TM(-O) (TM = Ti, Zr, Hf) solid solutions is conducted in this work. It is shown that Ti atoms in a Mo solid solution are strong traps for oxygen atoms, while Hf and, even more clearly, Zr atoms are not. It is pointed out that the ionic and covalent interactions are the primary influence on the trapping behavior, as the change in ionic and covalent interactions between trapping and nontrapping models follows the trend Mo-1Ti &gt; Mo-1Hf &gt; Mo-1Zr, which resembles the trend of the trapping energy.

Defect dynamics manipulates transport behaviors in highly stable rocksalt-type thermoelectric crystal

Adding Ge and Pb to the rock-salt SnTe triggers dynamic changes in the defect structures. As the doping level increases, these defects transit from densely dispersed dislocations to a network. Notably, the density of dislocations experiences a significant reduction when the Pb content exceeds a specific threshold value. For example, the alloy composition (Sn0.7Ge0.3)0.5Pb0.5Te demonstrates a solid solution behavior with limited linear defects. The fully dense (Sn0.7Ge0.3)0.5Pb0.5Te crystal shows reduced thermal conductivity κ and enhanced carrier mobility μ when compared to the pristine SnTe. Moreover, the single-leg device containing (Sn0.7Ge0.3)0.5Pb0.5Te achieves a remarkable efficiency η of 1.3 % across a temperature differential (∆T) of 280 K. This investigation successfully harnesses defect dynamics to manipulate the thermoelectric performance of IV-VI compounds while preserving their inherently stable rocksalt-type framework, all without undergoing phase transitions.

Defects passivity and UV emission characteristics in yttrium doped ZnO nanoparticles

Trivalent rare-earth Yttrium ions, Ydoped ZnO nanoparticles (NPs) and undoped NPs with chemical formulae Zn1-xYxO (x = 0–7 mol%) are synthesized by sol–gel auto-combustion (SGAC) technique. X-ray diffraction (XRD) analysis shows the solid-solution behaviour of Yions into ZnO matrix up to 1 mol% doping level. Raman spectra of the solid solution sample reveals an enhancement in the characteristic E2 vibrational modes and a subsequent lowering of the defects mediated Raman modes at higher doping levels. The undoped NPs exhibit enhanced luminescence characteristics whereas doped NPs present optimum luminescence characteristics at 1 mol% doping level due to effectual substitution of Yions. The corresponding results exhibited by Yttria (Y2O3) accommodated 2 and 5 mol% Y doped ZnO NPs match surprisingly with those of 0.5 mol% Y doped single phase NPs. The luminescence characteristics are suggested to be influenced by the fluctuations of charge clouds of O2–ions by Y3+ions of Zn-O-Y and Y-O-Y bonds.

Phase formation and unusual interstitial solid-solution strengthening behavior of (CoCrFeMnNi)Nx high-entropy ceramic films

High-entropy ceramic films (HECFs) have become promising industrial materials due to their excellent mechanical and functional properties. Achieving the precise design of HECFs has been a hot topic in recent years. Herein, the CoCrFeMnNi alloy, one of the most classic high-entropy systems, is chosen as the model to reveal the phase formation, growth, and properties of HECFs. Films were fabricated by magnetron sputtering at various N2-to-total (N2 + Ar) flow ratios (RN). Results show that the phase structure transformed from a semi-crystal phase to a single face-centered cubic (fcc) structure with increasing RN. Atomic migration ability affected by RN drives different growth processes, thereby constructing different microstructures, such as loose fiber structure and stacked particle structure. Moreover, the hardness exhibits a nonlinear relationship with interstitial solid solubility. Such unusual interstitial solid-solution strengthening behavior is attributed to the offset between solid-solution strengthening and grain boundary weakening as RN increases. A high hardness of 13.71 GPa and Young's modulus of 203.3 GPa are obtained in the (CoCrFeMnNi)Nx film deposited at RN = 20 %. This work not only explores an unusual interstitial solid-solution strengthening behavior, but also sheds light on the future HECFs design.

Dissolution of zirconium-cerium oxide solid solution in an aqueous system.

The solid-solution aqueous-solution (SSAS) system often involves dissolution/precipitation and redox reactions simultaneously. Comprehensive understanding of the SSAS system requires mechanistic insights into the dissolution mechanism of the solid solution based on reliable characterisation of the solid phases. Given this background, this study investigates the dissolution behaviour of zirconium-cerium oxide solid solution ((Zr,Ce)O2/(Ce,Zr)O2), which contains the redox-active metal Ce (Ce(III/IV)) and is of particular importance in the nuclear industry. The solid phases of the solid solution were comprehensively characterised by powder X-ray diffraction (PXRD) with Rietveld analysis and X-ray absorption spectroscopy (XAS) with factor analysis, indicating that the solid solution was primarily composed of tetragonal-(Zr,Ce)O2 and cubic-(Ce,Zr)O2. Water immersion of the solid solution leads to the dissolution of the solid phase at the solid-liquid interface. The addition of a reductant to the system reduces Ce(IV) in the solid solution to -(III) at the surface, promoting the dissolution of Ce from the solid-solution phase. The release of Ce from the solid solution also enriches the Zr content in the remaining solid-solution phase at the surface, which makes it more insoluble. This results in the formation of a protective layer at the solid surface, retarding further dissolution of the solid-solution phase.

Effect of V doping on the high temperature tribological properties of (Ti1−xVx)3AlC2 solid solutions sliding against different counterparts

The effects of Al content and the counterface material on the high temperature tribological behavior and wear mechanism of (Ti,V)3AlC2 solid solutions were investigated. The friction coefficient of (Ti0.6V0.4)3AlC2 is reduced by 36.25% and 47.76% compared to Ti3AlC2 at room temperature and 800 °C respectively. When coupled with Al2O3 and ZrO2 balls at 800 °C, continuous smooth lubricating films composed of oxides formed by the tribochemical reaction lead to the lower friction coefficients. When coupled with Si3N4 and SiC balls, the wear rates are relatively low due to the formation of friction films containing SiOx.

Solid Phase and Stability Investigation of a Co-Crystal in the l-Valine/l-Leucine System

Some amino acid systems are known to exhibit solid solution and/or co-crystal behavior upon crystallization, which significantly affects their phase diagrams and complicates the design of their purification processes. Such behaviors are observed in the l-valine/l-leucine system. In this work, the formation and stability of a 3:1 co-crystal of the two amino acids (designated as V3L) is further investigated. To accomplish the formation, liquid-assisted grinding, slurry equilibration, and sublimation experiments were performed and analyzed via HPLC and PXRD. Additionally, periodic DFT calculations were used to calculate lattice energies and determine the thermodynamics of possible solid phases. Experimental results show a clear metastability of the investigated V3L co-crystals when compared to its stable solid solution. The calculations underline the metastability and the possible formation of continuous solid solutions between l-valine and l-leucine since lattice energy differences between pure amino acids and mixed compositions are negligible. This previously unknown phase behavior can be used to assess the influence of V3L on the amino acid purification process and provides a basis for investigating similar systems with small energy differences between pure and mixed compositions in future studies. In addition, it demonstrates the particular variability of solid phases and their relationships in such simple but biologically important amino acid systems.

Mechanical properties and oxidation behavior of (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,Cr)AlB MAB solid solutions synthesized with spark plasma sintering

This study reports the effects of solid solution on the mechanical and oxidation behavior of MoAlB ceramics. (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,C)rAlB were synthesized under 30 MPa at 1200 °C by Spark Plasma Sintering (SPS). Composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS). Although it was determined that the main phase was MoAlB solid solution, it was observed that binary borides such as WB were also present in the (Mo,W)AlB and (Mo,W,Cr,)AlB. Hardness was measured by the Vickers indentation test. The hardnesses of MoAlB solid solutions improved considerably compared to pure MoAlB and were obtained as 13.65, 12.72, and 13.37 GPa, respectively, for (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,Cr)AlB. The reasons for the improvement in hardness are estimated to be grain refinement and solid solution hardening mechanism. Fracture toughnesses calculated from radial cracks formed during Vickers indentation are 6.52, 5.88, and 6.40 MPam1/2, respectively. Although crack bridging and deflection mechanisms work with solid solutions, as in pure MoAlB, the brittle binary borides in the structure did not improve fracture toughness. The oxidation test was carried out at 1200 °C for 12 h. A dense and continuous protective oxide layer was formed in all samples. The scale thicknesses of (Mo,W)AlB, (Mo,Cr)AlB, and (Mo,W,Cr)AlB are 3.2, 2.1, and 2.6 μm, respectively.

Mn‐Rich Phosphate Cathode for Sodium‐Ion Batteries: Anion‐Regulated Solid Solution Behavior and Long‐Term Cycle Life (Adv. Funct. Mater. 38/2023)

Mn‐Rich Phosphate Cathode for Sodium‐Ion Batteries: Anion‐Regulated Solid Solution Behavior and Long‐Term Cycle Life (Adv. Funct. Mater. 38/2023)

Structural Analysis of the Gd-Au-Al 1/1 Quasicrystal Approximant Phase across Its Composition-Driven Magnetic Property Changes.

Gd14AuxAl86-x Tsai-type 1/1 quasicrystal approximants (ACs) exhibit three magnetic orders that can be finely tuned by the valence electron concentration (e/a ratio). This parameter has been considered to be crucial for controlling the long-range magnetic order in quasicrystals (QCs) and ACs. However, the nonlinear trend of the lattice parameter as a function of Au concentration suggests that Gd14AuxAl86-x 1/1 ACs are not following a conventional solid solution behavior. We investigated Gd14AuxAl86-x samples with x values of 52, 53, 56, 61, 66, and 73 by single-crystal X-ray diffraction. Our analysis reveals that increasing Au/Al ordering with increasing x leads to distortions in the icosahedral shell built of the Gd atoms and that trends observed in the interatomic Gd-Gd distances closely correlate with the magnetic property changes across different x values. Our results demonstrate that the e/a ratio alone may be an oversimplified concept for investigating the long-range magnetic order in 1/1 ACs and QCs and that the mixing behavior of the nonmagnetic elements Au and Al plays a significant role in influencing the magnetic behavior of the Gd14AuxAl86-x 1/1 AC system. These findings will contribute to improved understanding towards tailoring magnetic properties in emerging materials.