Multicomponent Solid Solutions Research Articles

Machine learning for high-throughput experimental exploration of metal halide perovskites

<h2>Summary</h2> Metal halide perovskites (MHPs) have catapulted to the forefront of energy research due to the unique combination of high device performance, low materials cost, and facile solution processability. A remarkable merit of these materials is their compositional flexibility allowing for multiple substitutions at all crystallographic sites, and hence thousands of possible pure compounds and virtually a near-infinite number of multicomponent solid solutions. Harnessing the full potential of MHPs necessitates rapid exploration of multidimensional chemical space toward desired functionalities. Recent advances in laboratory automation, ranging from bespoke fully automated robotic labs to microfluidic systems and to pipetting robots, have enabled high-throughput experimental workflows for synthesizing MHPs. Here, we provide an overview of the state of the art in the automated MHP synthesis and existing methods for navigating multicomponent compositional space. We highlight the limitations and pitfalls of the existing strategies and formulate the requirements for necessary machine learning tools including causal and Bayesian methods, as well as strategies based on co-navigation of theoritical and experimental spaces. We argue that ultimately the goal of automated experiments is to simultaneously optimize the materials synthesis and refine the theoretical models that underpin target functionalities. Furthermore, the near-term development of automated experimentation will not lead to the full exclusion of human operator but rather automatization of repetitive operations, deferring human role to high-level slow decisions. We also discuss the emerging opportunities leveraging machine learning-guided automated synthesis to the development of high-performance perovskite optoelectronics.

Proton irradiation induced chemical ordering in an Al0.3CoFeNi high entropy alloy

The radiation resistance of single-phase high entropy alloys has been reported to be superior to conventional alloys, due to their high lattice distortion and sluggish diffusion kinetics. The current study combines the beneficial effects of a concentrated multi-component solid solution and chemical ordering on the parent lattice of a candidate alloy, Al0.3CoFeNi, to enhance proton radiation resistance. The strong ordering tendency in this alloy results in the formation of Ni-Al-rich short-range ordered (SRO) domains when it is annealed in a single FCC phase field and water quenched. The irradiation of these microstructures with high-fluence MeV-energetic protons aids the transformation of the prior metastable single FCC solid-solution with SRO domains toward a more stable condition with L12 long-range ordered (LRO) domains embedded within the FCC solid solution matrix. Potentially, the creation of radiation-induced vacancy cascades within the FCC solid-solution enhances local diffusivity aiding the transition from SRO domains to LRO L12 domains. Therefore, this can be considered as a recovery mechanism, since the radiation-induced damage is not allowed to accumulate and is minimized via nanometer-scale precipitation of the ordered intermetallic phase. Additionally, preferential Co segregation to defect clusters or dislocation loops was also observed. In comparison, purely thermal activation via annealing at 500 °C for 30 min induces a similar transformation from SRO to LRO in this alloy, driving the system closer to equilibrium.

Recommendations for simplified yet robust assessments of atomic mobilities and diffusion coefficients of ternary and multicomponent solid solutions

This study extends a 1-parameter Z-Z-Z binary diffusion coefficient model to ternary and multicomponent systems. The cross-binary and ternary interaction parameters in atomic mobility (diffusion coefficient) assessments were systematically tested on 4 ternary solid solutions: fcc Ag-Au-Cu, fcc Co-Fe-Ni, fcc Cu-Fe-Ni, and bcc Nb-Ti-V. A simple combination of the Z-Z-Z binary model parameters without any additional fitting parameters already provides impressive predictions of the ternary diffusion coefficients when the 3 cross-binary parameters are set to be the corresponding binary Z-Z-Z model interaction parameters, leading to a robust Z-Z-ternary diffusion model. Employment of 3 independent cross-binary fitting parameters leads to an even better binary and cross-binary parameters only (BCBPO) model. Recommendations are rendered based upon the amount of available experimental ternary diffusion coefficients. These recommendations will substantially reduce the number of fitting parameters and improve the robustness of the resultant atomic mobility and diffusion coefficient databases for computational materials design.

Elastic energy of multi-component solid solutions and strain origins of phase stability in high-entropy alloys

The elastic energy of mixing for multi-component solid solutions is derived by generalizing Eshelby's sphere-in-hole model. By surveying the dependence of the elastic energy on the chemical composition and lattice misfit, we derive a lattice strain coefficient λ*. Studying several high-entropy alloys and superalloys, we propose that most solid solution multi-component alloys are stable when λ*<0.16, generalizing the Hume-Rothery atomic-size rule for binary alloys. We also reveal that the polydispersity index δ, frequently used for describing strain in multi-component alloys, directly represents the elastic energy (e) with e=qδ2, q being an elastic constant. Furthermore, the effects of (i) the number and (ii) the atomic-size distribution of constituting elements on the phase stability of high-entropy alloys were quantified. The present derivations and discussions open for richer considerations of elastic effects in high-entropy alloys, offering immediate support for quantitative assessments of their thermodynamic properties and studying related strengthening mechanisms.

Optical and electrical properties of hard (Hf,Nb,Ti,V,Zr)Nx thin films

(Hf,Nb,Ti,V,Zr)Nx coatings with nitrogen content between 0 and 49 at.% were deposited by sputter deposition, and thoroughly characterised. Nitrogen-free coatings were found to have a bcc structure, low hardness (8 GPa), and an electrical resistivity of 144 μΩcm. The nitride coatings (43–49 at.% N) had NaCl-type structure, consistent with a multi-component solid solution phase. Photoelectron core level binding energies indicate that the electronic structure of the multi-component nitride differs from that of the binary nitrides, probably a result of charge transfer between the metal atoms. The nitride coatings exhibited a dense microstructure and a hardness between 29 and 33 GPa, and electrical resistivities of 141–254 μΩcm. They also exhibited a minimum in the optical reflectance, similar to that of TiN, indicating plasmonic properties. The position of this minimum was found to be shifted to smaller wavelengths (272–339 nm) compared to a TiN reference (428 nm) and varied with nitrogen content. The tuneability of the optical properties, in combination with the potential to influence the electronic structure through charge transfer between metal atoms point to new interesting routes to design optical materials, and a new class of optical materials based on the concept of multi-component nitrides.

Shift of the Infrared Absorption and Emission Spectra of Transition Metal Ions in Solid Solutions of Semiconductor Compounds

A universal theoretical model is proposed that explains the observed shift of IR absorption and emission bands in the spectra of transition metal ions in solid solutions of semiconductor compounds. The model has been used for estimating the long-wavelength shift of luminescence bands in the spectra of semiconductor solid solutions with increasing concentration in application to crystals of the ternary systems ZnMgSe(Cr2+) and CdMnTe(Fe2+). Description of the phenomenon is generalized to the case of multicomponent solid solutions.

New mechanism and criterion for forming multi-component solid-solution alloys

Some existing criteria for forming single-phase multicomponent solid-solution alloys (MCSSAs) are assessed, and a new criterion based on the topology of atomic packing is propounded. A new mechanism concerning the development of MCSSAs is posited, where the multicomponent effect in surface layer, reducing the surface free energy of nanocrystalline nucleus, plays a significant role. More reasonable interpretation regarding the phase stability of CoCrFeMnNi alloy annealed at different temperatures is provided.

Oxidation behavior of non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution powders in air

Multi-component solid solutions with non-stoichiometric compositions are characteristics of ultra-high temperature carbides as promising materials for hypersonic vehicles. However, for group IV transition-metal carbides, the oxidation behavior of multi-component non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution has not been clarified yet. The present work fabricated four kinds of (Zr,Hf,Ti)Cx carbide solid solution powders by free-pressureless spark plasma sintering to investigate the oxidation behavior of (Zr,Hf,Ti)Cx in air. The effects of metallic atom composition on oxidation resistance were examined. The results indicate that the oxidation kinetics of (Zr,Hf,Ti)Cx are composition dependent. A high Hf content in (Zr,Hf,Ti)Cx was beneficial to form an amorphous Zr-Hf-Ti-C-O oxycarbide layer as an oxygen barrier to enhance the initial oxidation resistance. Meanwhile, an equiatomic ratio of metallic atoms reduced the growth rate of (Zr,Hf,Ti)O2 oxide, increasing its phase stability at high temperatures, which improved the oxidation activation energy of (Zr, Hf, Ti)Cx.

Multifractal features of the microstructure in hard and soft ferroelectric ceramic materials

The results of comparative multifractal studies of the grain structure of different ceramic piezoelectric materials are presented. Hard and soft ferroelectric ceramic materials as well as materials with medium ferroelectric hardness were studied. The relationship of ceramics microstructure with the formation of the target properties in materials was discovered and analyzed. Promising approaches to improving the technology for producing ferroelectric and piezoelectric ceramics based on multicomponent solid solutions are proposed. Probable directions for future research are discussed.

Observations of multi-component boride precipitates in ultrahard boron carbide

Boron carbide (B4C) often consists of intrinsic secondary phase precipitates that are formed during the reaction-sintering process. These precipitates not only play an important role during the densification process but also affect the mechanical properties of B4C. In the present study, the structural determination of multicomponent secondary phases that are precipitated out in monolithic B4C was investigated using atomic resolution scanning transmission electron microscopy (STEM) and atom probe tomography (APT). Here we found two types (Type-I and II) of multicomponent boride nano-precipitates in B4C i.e. (i) elongated precipitates (type-I), identified as (Cr(1-x-y)-Fex-Wy)3B4 phase, rich in chromium (Cr), Iron (Fe), tungsten (W), and boron (B) (ii) equiaxial (type-II) precipitates that are rich in titanium (Ti), Cr, and B in form of Ti(1-x)CrxB2 phase. The estimated reduced modulus and hardness using depth sensitive nanoindentation on type-I precipitates were 335 ± 6 GPa and 32 ± 2 GPa and that in type-II precipitates were 268 ± 13 GPa and 22 ± 3 GPa, respectively. These results underscore the importance of multicomponent solid solution hardening in ultra-hard B4C material.

Microdistortions, Hardness, and Young’s Modulus of Multicomponent Bcc Solid Solutions

The phase composition, type II microstresses, and coherent scattering domains (CSDs) of multicomponent (medium- and high-entropy) bcc solid solutions with an average electron concentration, Csd, ranging from 4.6 to 5.47 e/a were studied. The effect of these characteristics on the hardness and Young’s modulus was analyzed. The alloys were melted in a MIFI-9 vacuum arc furnace using components with a purity of at least 99.5 wt.%; the ingots were remelted six times. The hardness and Young’s modulus of the alloys were determined from nanoindentation curves plotted with a Micron Gamma unit under a load from 0.98 to 2.94 N using a Berkovich diamond pyramid under automated loading and unloading. A relatively small change in the quantitative chemical composition of the samples led to a noticeable change in the lattice parameter, type II microstresses, CSDs, microhardness, and Young’s modulus. The greatest possible type II microstresses and minimum CSD sizes were observed for the alloys characterized by high average mismatch between the atomic sizes of their constituent elements. Increase in the electron concentration in the alloys led to higher hardness and Young’s modulus and lower lattice parameter. Increase in the type II microstresses was also accompanied by higher hardness and Young’s modulus. The microhardness H of alloys significantly exceeded that calculated with the mixture rule, Hmix, and was determined by solid-solution hardening (∆H = H – Hmix ranging between 2.9 and 6.4 GPa). Type II microstresses precisely calculated from the X-ray line width can be used for measuring the distortion of the solidsolution lattice and assessing solid-solution hardening. The relationship between the magnitude of solid-solution hardening, Young’s modulus, and lattice microdistortions (type II microstresses) was proposed.

Spontaneous formation of filled-shell CsI-Xenon solid solutions under high temperature and high pressure

Different stoichiometries compounds formed by filled-shell (FS) insulators (e.g., xenon) have been extensively predicted and successfully synthesized under extreme conditions. However, theoretical prediction on solid solution formed by FS materials is lacking. Here, by combining structure searching and ab initiohybrid Metropolis-Monte Carlo/molecular dynamics simulations, we predict that the noble gas xenon and CsI can form thermodynamically stable substitutional solid solutions with hexagonal close-packed at high temperature and high pressure, in which Xe, Cs and I exhibit similar electronegativity and strong metallic feature that are analogous to the solid solution alloys. The existence of short-range order among constituent compositions improves the stability of solid solution. These results shed a new insight on the chemical reactivity between noble gases and alkali-halide compounds and provide valuable reference to understand the formation of multicomponent solid solutions under extreme conditions.

Дифференциальная туннельная проводимость в многокомпонентных твердых растворах Bi-=SUB=-2-x-=/SUB=-Sb-=SUB=-x-=/SUB=-Te-=SUB=-3-y-z-=/SUB=-Se-=SUB=-y-=/SUB=-S-=SUB=-z-=/SUB=-

Differential tunnel conductance of the interlayer van der Waals surface (0001) was investigated in n-Bi2-xSbxTe3-y-zSeySz multicomponent solid solutions at x = 0.2, y = z = 0.09, optimized for near room temperatures with a high power factor, and at x = 0.4, y = 0, z = 0.06 with optimal thermoelectric properties for low temperatures and a high Seebek coefficient. It is shown that the intensity of the fluctuations of the Dirac point energy, a shift the top of the valence band and presence of surface levels in the energy gap formed by impurity defects is determined with composition and thermoelectric properties of solid solutions. The contribution of the surface states of Dirac fermions increases in n-Bi1.8Sb0.2Te2.82Se0.09S0.09 solid solution with a high power factor due to significant decrease of the surface concentration near the charge neutrality point and the growth of fermion mobility.

Comparative Analysis of the Phase Composition of Irradiated Uranium-Plutonium Nitride under Joint Influence of Carbon and Oxygen Impurities and β-Decomposition of Some Fission Products

Thermodynamic simulation demonstrated that the accumulation of fission products in irradiation of a uranium-plutonium nitride with admixture of carbon and oxygen (U0.8Pu0.2)(N0.9475O0.02625C0.02625) results in that a multicomponent oxycarbonitride solid solution is formed. This solid solution contains U, Pu,Am, Np, Zr, Y, and lanthanides as well as separate oxide (BaUO3, SrPuO3), carbide (URu3C0.7, Mo2C), and nitride (U2N3) phases and intermetallides U(Rh,Pd)3. The β– decay of metallic radionuclides in separate oxide and carbide phases of spent nuclear fuel changes their chemical and phase compositions, The transformation kinetics of separate phases 99Mo2C → 1/399Tc6C + 2/3 C, 140BaUO3 →1/2140Ce2UO6 + 1/2U was calculated.

ПЕРСПЕКТИВЫ ПРИМЕНЕНИЯ ВЫСОКОЭНТРОПИЙНЫХ СПЛАВОВ ДЛЯ ВОССТАНОВЛЕНИЯ ДЕТАЛЕЙ МАШИН АТМОСФЕРНЫМ ПЛАЗМЕННЫМ НАПЫЛЕНИЕМ

A brief analysis of the most common methods for producing multicomponent alloys, including high-entropy alloys (HES), is presented in terms of their use as an alternative to coatings made of traditional structural metal materials. Preliminary studies of the microstructure and phase compo-sition of the coating obtained by plasma deposition of FeCoCrAlTiCuMo powder in the equiatom-ic ratio of components are presented. The results of the research showed the possibility of obtain-ing a multicomponent single-phase solid solution by plasma sputtering and indicated the feasibil-ity of its further study.

Прогнозирование условий хлоридно-гидридной эпитаксии слоев Ga1–yInyAs1–xPx, изопериодных с GaAs и GaAs1–xPx

Multicomponent solid solutions of AIIIBV are increasingly used in optoelectronics, photonics, and other fields of science and technology. These are AlGaInN-based emitters, InGaAsP-based receivers, etc. In addition, these materials are widely used as buffer and isomorphic layers in general-purpose nanoheterostructures. The main methods of their production are gas-phase methods, such as chloride-hydride, MOS-hydride epitaxy, MBE. The development of optimal technological modes of multicomponent layers and structures, as a rule, takes a lot of time and is quite expensive. In this paper, the author proposed a method for modeling processes based on the basic physical and chemical laws of the crystallization processes of materials and the properties of AIIIBV compounds. The analysis and prediction of the processes of obtaining four-component solid solutions In1–yGayAs1–xPx, isoperiodic with GaAs, three-component solid solutions GaAs0,8P0,2 and GaAs0,6P0,4 were performed. The calculated modes have been experimentally implemented and the materials corresponding to the current level of quality have been obtained.

Сдвиг инфракрасных спектров поглощения и излучения ионов переходных металлов в твердых растворах полупроводниковых соединений

A universal theoretical model explaining the effect of the shift of absorption and emission bands of transition metal ions in solid solutions of semiconductor compounds is proposed. By the example of ternary compounds Zn1-xMgxSe:Cr2+ and Cd1-xMnxTe:Fe2+, an estimate of the typical parameters of the long-wavelength shift of absorption and luminescence in the mid-infrared range with increasing of concentration of solid solution is performed. A generalization of the effect to the case of multicomponent solid solutions is considered.

New Mechanism and Criterion for Forming Multi-Component Solid-Solution Alloys

Some existing criteria for forming single-phase multicomponent solid-solution alloys (MCSSAs) are assessed, and a new criterion based on the topology of atomic packing is propounded. A new mechanism concerning the development of MCSSAs is posited, where the multicomponent effect in surface layer, reducing the surface free energy of nanocrystal nucleus, plays a significant role. More reasonable interpretation regarding the phase stability of CoCrFeMnNi alloy annealed at different temperatures is provided.

Solid solution of semiconducting contorted small molecules for high-performance Li/Na-ion host electrodes

Multicomponent solid solutions have attracted wide attention because they have great potential to improve the physical and chemical properties of pure materials. However, there are stringent prerequisite conditions, such as shape similarity and isomorphism of the crystal phase, for forming a solid solution. These conditions have not been studied extensively in organic solid solution materials, although they have great advantages in terms of the energy storage properties of materials. Herein, we investigate the solid solution of semiconducting contorted hexabenzocoronene (cHBC) and its tetra-fluorinated derivative (FcHBC) as small molecules for a high-performance Li/Na-ion host electrode. Our systematic study, combined with a grazing incidence wide-angle X-ray scattering (GIWAXS) characterization and a computational study thereof, reveals that the molecular interrelationship between cHBC and FcHBC molecules forms P21/n crystal phase of cHBC/FcHBC solid solution owing to their similar molecular and crystal structures. The continuous solid solution of cHBC/FcHBC electrodes, in particular, not only effectively enhances the electron charge transfer without adding the conducting agent but also delivers a better rate capability as both Li- and Na-ion hosting electrodes. Furthermore, the solid solution electrodes maintain a reliable cycling performance in the conventional aprotic electrolyte, which suggests that organic solid solution electrodes are promising organic electroactive materials for alkali ion-based energy storage cells.

Assessing the magnetic order dependent γ-surface of Cr-Co-Ni alloys

In order to efficiently explore the nearly infinite composition space in multicomponent solid solution alloys for reaching higher mechanical performance, it is important to establish predictive design strategies using computation-aided methods. Here, using ab initio calculations we systematically study the effects of magnetism and chemical composition on the generalized stacking fault energy surface (γ-surface) of Cr-Co-Ni medium entropy alloys and show that both chemistry and the coupled magnetic state strongly affect the γ-surface, consequently, the primary deformation modes. The relations among various stable and unstable stacking fault energies are revealed and discussed. The present findings are useful for studying the deformation behaviors of Cr-Co-Ni alloys and facilitate a density functional theory based design of transformation-induced plasticity and twinning-induced plasticity mechanisms in Cr-Co-Ni alloys.