High-entropy Films Research Articles

A significant improvement in corrosion resistance and biocompatibility in ZrNbTiCrCu high-entropy films induced by the precipitation of Cu

Utilizing nanotechnology and composites to create a protective film on titanium alloy is an effective means of achieving the desired high performance. Self-assembly of nanocomposite structures offers a promising route to forming high entropy alloy films (HEAFs), but controlled preparation remains challenging. This work used magnetron sputtering through adjusting preparation parameters to prepare ZrNbTiCrCu HEAFs, achieving a significant improvement in corrosion resistance and biocompatibility induced by the precipitation of Cu. According to the electrochemical corrosion test, without obvious corrosion pits on the surface of S2 after corrosion, a passivation film composed of bimetallic oxide CuCrO2 formed on the film surface, indicating that ZrNbTiCrCu HEAFs have remarkable corrosion resistance performance. In the cytocompatibility experiment, the cell viability of HEAFs reached over 95 % due to the precipitation of Cu, suggesting their excellent biocompatibility. In addition, ZrNbTiCrCu HEAFs exhibit outstanding antibacterial ability, especially when the sputtering current is 0.6 A, and the in vitro antibacterial rate of the sample against Escherichia coli is close to 99 %.

Component regulation and high-entropy engineering for enhanced antioxidant and high-temperature mechanical properties of protective films

Transition metal nitrides (TMNs) have gained widespread application in protecting structural components due to their high strength and hardness. However, TMNs still have the challenge of structural instability and mechanical deterioration caused by oxidation under harsh high temperature conditions. Herein, we present a strategy combining component regulation with high-entropy engineering to develop an advanced high-temperature Al-containing high-entropy nitrides (HENs) material. To prevent the phase decomposition of AlN within the (NbMoTaWAl)N, theoretical simulations were employed to determine a critical atomic percent of 25.0% Al for maintaining the stability of the high-entropy structure. Ensuing experimental synthesis creates three NbMoTaWAlN films with varying Al content: a high-entropy film with 0.0% Al (HEN), a high-entropy film with 21.2% Al (HEN-Al), and an amorphous transition metal nitride film with 30.2% Al (a-TMN-Al), validating key high-entropy engineering benchmarks. It is found that the unique HEN-Al film exhibits excellent oxidation resistance and high-temperature hardness, attributed to the uniform distribution of Al atoms in the robust high-entropy structure, which creates conditions for forming a dense and continuous Al2O3 barrier layer, effectively hindering the diffusion of oxygen into the film interior. This study provides new insights to develop a new generation of high-temperature protective materials.

Plasma Bombardment-Induced Amorphization of (TiNbZrCr)Nx High-Entropy Alloy Nitride Films

The (TiNbZrCr)Nx high-entropy nitride films (HENFs) were prepared by high-power pulsed magnetron sputtering (HPPMS). The effect of the N2 flow rate (FN) on the HPPMS plasma discharge, film composition, microstructure, residual stress, tribological properties, and corrosion resistance was investigated. Results show that, with the increase in FN, plasma discharge is enhanced. Firstly, the introduced N atoms react with Ti, Nb, Cr, and Zr to form an FCC nitride phase structure. Then, with the increase in plasma bombardment on the deposited film, the HENFs undergo amorphization to form an FCC+ amorphous structure, accompanied by a decrease in grain size and a change in the preferred orientation from (1 1 1) to (2 0 0). The HENFs deposited at FN = 8 sccm show the highest hardness of 27.8 GPa. The HENFs deposited at FN = 12 sccm present the best tribological properties, with a low wear rate of 4.0 × 10−6 mm3N−1m−1. The corrosion resistance of the (TiNbZrCr)Nx HENFs shows a strong correlation with the amorphous phase. The corrosion resistance of the FCC nitride film is the worst, and the corrosion resistance gradually increases with the amorphous transformation of the film. Based on the above results, nanocomposite high-entropy films can be prepared using HPPMS technology and exhibit excellent, comprehensive performance.

Robust Low-Friction and Low-Wear TiNbMoTaCr High-Entropy Film Enabled by Periodically Inserting Curved MoS2 Sheets.

The well-known integration of physical, chemical, and mechanical properties enables high-entropy alloys (HEAs) to be applied in various fields; however, refractory HEAs are brittle and susceptible to abrasive wear at high coefficients of friction (COF), resulting in insufficient mechanical durability against abrasion. Herein, curved MoS2 nanosheets are periodically introduced into the TiNbMoTaCr film for triggering the self-assembly mixed metal oxides @MoS2 nanoscrolls, which contain hard mixed metal oxides cores and the low-shearing lubricant MoS2 shells, during the friction in the air environment; such mixed metal oxides@MoS2 nanoscrolls in the friction interfaces can contribute to the robust low friction and low wear. Compared to the pure TiNbMoTaCr film (with high COF of ∼0.78, low abrasive durability identified by worn-out event), the periodic incorporation of 10 nm thickness curved MoS2 sheets can successfully achieve a low COF of ∼0.08 and low wear rate of ∼9.561 × 10-8 mm3/ Nm, much lower than the pure MoS2 film (COF = ∼ 0.21, wear rate = ∼ 1.03 × 10-6 mm3/ Nm). Such superior tribological properties originate from the cooperative interaction of TiNbMoTaCr nanolayers and curved MoS2 nanosheets, accompanied by the self-assembly of mixed metal oxides@MoS2 nanoscrolls. In these nanoscrolls, TiNbMoTaCr can act as an 'air-absorbing agent' to form high-loading mixed metal oxide cores and serve as an 'oxygen sacrificer,' preventing the low-shearing lubricant curved MoS2 nanosheets from oxidation. In addition, even with the soft MoS2, the hardness of the TiNbMoTaCr/MoS2 nanomultilayers can still be well maintained and increased above the calculated values by mixing law, further favoring superior mechanical durability. The synergetic effect of TiNbMoTaCr and curved MoS2 nanosheets during the friction in air can provide a route to design HEA films with enhanced tribological properties for better mechanical durability and broader application prospects.

The barrier-free nanomultilayered structure via enthalpy-mediated phase separation in refractory high-entropy films

Patterned metal systems to periodically modulated nanomultilayered architectures, with crystalline and/or amorphous states, has acted as an effective strategy for tuning desirable mechanical properties. While the spontaneous assembly offers an effective and promising path for constructing nanomultilayers, in high-entropy alloys (HEA) how to trigger such a barrier-free route still faces challenges. In this paper, the enthalpy-difference-guided strategy, incorporating Pt, was employed to induce spinodal decomposition for the barrier-free nanomultilayer structure in refractory HEA systems. Aiming at exploring the elastic and chemical interactions, three HEA films with different degrees of size mismatch δ (Zr-Nb-Ta-Mo-W, Zr-Hf-Nb-Ta-Mo, Zr-Hf-Nb-Cr-Mo systems) were fabricated as model systems. Contributed by differences in ΔHmix and δ, in each HEA film, certain-content Pt can trigger both spinodal decomposition and amorphization behavior, which lead to the barrier-free Pt-rich/Pt-lean nanomultilayers with different topological combinations: crystalline/crystalline and amorphous/amorphous. Compared to model HEAs, such barrier-free nanomultilayers can significantly improve the nanoindentation hardness. In HEA systems, tuning ΔHmix and δ simultaneously can assist the further understanding of the structural arrangements and the progress on the barrier-free nanomultilayered configuration for superior mechanical properties.

Microstructure, mechanical properties and tribological behavior of (TiZrHfNbTa)Nx high entropy films deposited by magnetron sputtering

High entropy nitride (HEN) films of (TiZrHfNbTa)Nx were deposited by reactive DC magnetron sputtering, choosing 304 stainless steel and silicon wafers as the experimental substrates. The influence of nitrogen flow rate RN: N2/(N2+Ar) on the microstructure and properties of HEN films was investigated. The results showed that HEN films exhibit granular surface morphologies and internal characteristics of amorphous embedded FCC crystals, exhibiting a structure of amorphous at the lower RN (0, 2 %) and transforming to FCC crystals with preferred (111) orientation as RN increasing (6.5%–26 %), with the decrease of crystallinity and the alteration of preferred orientation from (111) to (200) at the further increase of RN at 40 %. The introduction of nitrogen led to significant improvements of film hardness (>23 GPa) and modulus (>270 GPa). When RN = 13 %, the hardness is up to 30.7 GPa, and the modulus is 340 GPa at RN = 6.5 %. The as-deposited films exhibited excellent wear resistance, and the wear rate (6.65✕10−6mm3/Nm) was the lowest when RN = 2 %.

Design of high-entropy films as ultra-violet light reflector

This study proposes the design and implementation of high-entropy alloy (HEA) thin films as materials for the reflector of deep ultraviolet light-emitting devices and marks the first application of HEA in optical field. In the material design phase, an Al-Co-Zn-Ni alloy is designed by considering the reflectivity, phase stability and binary formation energy. Reverse Monte Carlo calculation is employed to establish stable atomic structure. Frequency-dependent dielectric equations are derived from first principles calculations, with dielectric constants incorporating contributions from ions and electrons and combining classical Drude and Lorentz models. The dielectric equations yield optical constants that are used to calculate the reflectance. In the experimental phase, we systematically vary the aluminum content and prepare Al-Co-Zn-Ni thin films ranging from pure aluminum to equimolar compositions. In the deep ultraviolet region, the reflectance of thermally treated Al65Zn12Co12Ni11 and Al50Zn16Co17Ni17 thin films is found superior to that of gold by three times. Structural and crystalline changes with varying aluminum content are found, as well as intriguing phase separation and superlattice formation that persist until equimolar compositions. This unique nanoscale structural variation causes the Young's modulus and hardness of Al-Co-Zn-Ni thin films to initially increase and then decrease with decreasing aluminum content. There is a significant increase in the corrosion potential difference when reducing Al contents in Al-Co-Zn-Ni, indicating improved passivation effects as the equimolar composition is approached. By modulating the aluminum content, the nanoscale structure of Al-Co-Zn-Ni can be adjusted, thereby improving its optical, mechanical, corrosion resistance, and thermal stability properties. This demonstrates the high versatility of this material for practical optical applications.

Oxidation resistance and mechanical properties of AlTiZrHfTa(-N) high entropy films deposited by reactive magnetron sputtering

(AlTiZrHfTa)1−xNx refractory high entropy films (RHEFs) were deposited by direct current magnetron sputtering in various nitrogen ratios (RN2 = N2/(Ar+N2)) on flat glass, silicon and sapphire substrates. The nitrogen-free film is amorphous while the nitrides are single-phased solid solutions with Face-Centered Cubic (FCC) structures. The hardness increases from 6.4 GPa for the nitrogen-free film to 25.3 GPa for the film obtained at RN2 = 20%. A preferred orientation from (111) to (200) occurs when RN2 increases from 5% to 50%. H/E and H3/H2 reports show high values for the film deposited at RN2 = 20% compared to that at 10%. However, this latter has the best compromise in terms of mechanical properties related to a lower residual stress value. The nitrides films obtained with RN2 ≥ 5%, are thermally stable at 800 °C for 3 h under vacuum. Compared to the metallic film they show an improved oxidation resistance. In fact, the Kp constant of the nitride (RN2=20%) is lower (1.22 10−7 g2 cm−4 h−1) than that of the nitrogen-free film (1.77 10−6 g2 cm−4 h−1). The corresponding activation energies (Ea) are respectively calculated at 94.8 KJ. mol−1 and 45.5 KJ.mol−1. After oxidation process, TEM analysis reveal the formation of homogeneous mixed oxide.

Integration of hardness and toughness in (CuNiTiNbCr)Nx high entropy films through nitrogen-induced nanocomposite structure

The high-entropy alloy films show excellent comprehensive properties and have great application prospects in space, polar, deep-sea exploration. Compared with traditional ceramic films, the application of high-entropy alloy films is limited by the relative low hardness. In this paper, based on the nanocomposite structure formation principle in thermodynamics, we design the nanocomposite (CuNiTiNbCr)Nx films (HEFs). The introduced N atoms react with Ti, Nb, Cr to form (TiNbCr)N phase (accompanied by Cu and Ni segregation), and the structure of the HEFs changes from amorphous to a nanocomposite structure of CuNi-rich amorphous matrix-(TiNbCr)N nanocrystalline phase. The nanocomposite HEFs exhibit high hardness, high toughness, and excellent wear performance. These results indicate that nanocomposite HEFs have potential applications in the field of extreme environmental wear protection.

Hard yet tough and self-lubricating (CuNiTiNbCr)Cx high-entropy nanocomposite films: Effects of carbon content on structure and properties

The single-phase high-entropy alloy film is difficult to meet severe friction conditions due to its low hardness and high friction coefficient. Nano-composite structure film is composed of at least two separated phases, showing the properties of strength and toughness integration and excellent wear resistance. The design of nanocomposite structures can effectively improve the mechanical properties and tribological properties of high-entropy alloy films. In this study, the (CuNiTiNbCr)Cx nanocomposite high-entropy films (HEFs) integrated with high hardness, high toughness, and self-lubrication were synthesized by the double-target co-sputtering method. The effect of carbon content on microstructure, mechanical properties, and tribological properties of (CuNiTiNbCr)Cx films was studied. With the increase of carbon content in the HEFs, the carbon atoms preferentially react with Ti, Nb, and Cr to form a (TiNbCr)C ceramic-reinforced phase, and then the excess carbon atoms precipitate in the form of amorphous carbon (a-C) lubricating phase in the HEFs. The structure of the HEFs changes from an amorphous structure to a nanocomposite structure of amorphous (amorphous CuNiTiNbCr phase + a-C phase)/nanocrystalline (TiNbCr)C phase. When the carbon content is about 21.2 at.%, the carbide phase in the film reaches saturation and the hardness and modulus of the films are highest, which are 18 GPa and 228 GPa, respectively. The HEFs with a carbon content of 44.0 at.% show the best toughness and tribological properties with a friction coefficient of 0.16 and a wear rate of 2.4 × 10–6 mm3/(N m), which is mainly attributed to the excellent resistance to fatigue crack growth and the interfacial lubricating layer formed in the friction process. The nanocomposite (CuNiTiNbCr)Cx HEFs show very promising application prospect in the field of friction protection.

The Effect of Yttrium Addition on Microstructure and Mechanical Properties of Refractory TiTaZrHfW High-Entropy Films

Refractory high-entropy films (RHEFs) are a new type of high-temperature material with great prospects for applications due to their superior properties. They have the potential to replace nickel-based superalloys in order to develop a new generation of materials that can be used under extreme conditions. (TiTaZrHf)100−xYx RHEFs are prepared using the magnetron sputtering technique. The yttrium (Y) content varies from 0 to 56 at.%. XRD analysis indicates the formation of an amorphous phase in Y-free films, while new phases are formed after the addition of Y. The results are confirmed by TEM analysis, revealing the formation of nano-grains with two phases L12 and Y-P6/mmm structure. With an increasing Y content, the grain size of the nano-grains increases, which has a significant effect on the mechanical properties of the films. Hardness decreases from 9.7 GPa to 5 GPa when the Y amount increases. A similar trend is observed for the Young’s modulus, ranging from 111.6 to 82 GPa. A smooth and featureless morphology is observed on the low Y content films, while those with a larger Y content appear columnar near the substrate. Furthermore, the phase evolution is evaluated by calculating the thermodynamic criteria ΔHmix, ΔSmix, Ω, and δ. The calculation results predict the formation of new phases and are then in good agreement with the experimental characterization.

Superconductivity in (TaNb)1–x(ZrHfTi)xMoy high-entropy alloy films

Superconducting high entropy alloys (HEAs) are a novel class of superconductors, with applications for electronic devices. Here, we investigated the effect of Mo alloying on superconducting properties of high entropy films with the composition (TaNb)1–x(ZrHfTi)xMoy. For near-equimolar composition, the crystalline HEAs grains are transformed into amorphous aggregations with a size in a few nanometer scale, forming a crystal/glass nanocomposite. In both crystalline and amorphous HEAs, the constituent atoms exhibit a homogeneous random distribution. The entropy-affected phase formations suppress the superconducting transitions in HEAs, which broadens the normal-to-superconducting transition regime and suppresses the zero-resistivity critical temperature to a lower constant value of approximately 2.9 K.

High-temperature wear and oxidation behavior of (CrNbTaMoVW)N high entropy films deposited by reactive magnetron sputtering

Rapid advancements in industrial technology necessitate mechanical parts capable of operating at high temperatures. High entropy alloy films have emerged as promising material for high-temperature resistant coatings, providing improved friction control and wear reduction. In this study, (CrNbTaMoVW)N high-entropy films were fabricated on YG6 cemented carbide substrates using reactive DC magnetron sputtering. The oxidation and tribological performance of the films were investigated across a temperature range from room temperature to 800 °C. Oxidation results revealed that (CrNbTaMoVW)N film maintained its simple Face-Centered Cubic (FCC) structure up to 600 °C for 3 h in the presence of air. At 800 °C, complete oxidation occurred, resulting in the formation of complex metal oxides and metal oxynitrides, and a structural transformation from FCC to these compounds. Following oxidation at 600 °C for 3 h, High-Entropy Alloy (HEA) film exhibited the maximum values of hardness (30.6 GPa) and modulus (301.7 GPa). Tribological results demonstrated an increase in both friction coefficient and wear rate with rising test temperature. However, (CrNbTaMoVW)N film showed a relatively low wear rate ranging from room temperature to 600 °C, approximately 10−15 m3/N•m, thus indicating excellent high-temperature tribological properties. Notably, the wear resistance of (CrNbTaMoVW)N film was significantly compromised at 800 °C due to the formation of loosely bonded metal oxides with reduced hardness, in contrast to the test temperature of 600 °C.

Multilayer amorphous-crystalline high-entropy metal films

High-entropy alloys (HEA) are multi-element materials and contain at least five elements of similar concentration. HEA are, as a rule, single- phase thermodynamically stable substitutional solid solutions, mainly based on a body-centered cubic and face-centered cubic crystal lattice. Solid solution stabilization during the crystallization of a high-entropy alloy is provided by the interaction of a number of factors, namely, a high mixing entropy and low diffusion rate of components, and a low growth rate of crystallites from the melt. The purpose of this work was to obtain new knowledge about the structure and properties of high-entropy films synthesized on a metal substrate during deposition of a multi-element metal plasma in argon atmosphere. The plasma was formed as a result of independent plasma-assisted electric arc cathodes of the following metals: Ti, Al, Cu, Nb, Zr sputtering. As a result of the performed studies, the deposition mode was revealed, which allows the formation of films of various thicknesses of close to equiatomic composition. Transmission electron microscopy methods have established that the films are multilayer formations and have nanoscale amorphous-crystalline structure. Microhardness of the films significantly depends on the ratio of number of the forming elements and varies from 12 to 14 GPa, Young’s modulus – from 230 to 310 GPa. Crystallization of the films was carried out by irradiation with a pulsed electron beam. As a result of processing, a two-phase state is formed. The main phase is α-NbZrTiAl with a volume-centered cubic crystal lattice with a parameter of 0.32344 nm; the second phase of CuZr composition has a simple cubic lattice.

Enhancement of oxygen evolution reaction performance of FeCoNiCrMn high entropy alloy thin film electrodes through in-situ reconstruction

Due to the large number of defects and high entropy properties, high entropy alloy thin film electrodes prepared by magnetron sputtering are beneficial for electrocatalytic oxygen evolution reaction (OER). However, the electrocatalytic OER performance of high entropy alloy thin film electrodes without activation is limited. In this work, in-situ reconstruction (chloride corrosion) is applied to activate FeCoNiCrMn high entropy alloy thin film electrodes for promoting the electrocatalytic OER performance. The research reveals that high entropy hydroxides and high entropy (oxy)hydroxides, which are real active centers of OER electrocatalysts, are generated on the surface of FeCoNiCrMn high entropy film electrodes during in-situ reconstruction. Moreover, it is also proved that there is an obvious quantitative relationship among elements in the surface of the high entropy alloy thin film electrodes after complex chloride corrosion reaction: Ni>Mn>Fe>Co>Cr. In addition, the OER performance of FeCoNiCrMn high entropy film electrodes with in-situ reconstruction can achieve an overpotential of 263 mV and a Tafel slope of 50.9 mVdec−1. Moreover, sponge-like structures created by in situ reconstitution can help to increase surface active areas and the increased contents of high-valence elements after in situ reconstruction contribute to enhance electrocatalytic OER activity.

Structure and properties of ion-plasma deposited films of CoCrFeMiMn high-entropy alloy

High-entropy Co19Cr18Fe22Mn21Ni20 thin films were obtained by the modernized method of three-electrode ion-plasma sputtering of mosaic targets consisting of pure metals. The structure, electrical resistance, and magnetic properties of films were investigated. Single diffuse halo was seen on the XRD patterns of the as-deposited films, which confirms their amorphous structure. Some of the thin films, which were annealed at 900 K in a vacuum, were identified to be oxidized by a small amount of oxygen in the work chamber. After the heat treatment, the Co19Cr18Fe22Mn21Ni20 films were transformed from an amorphous state into a crystallized FCC solid solution with the lattice parameter a=0.3613 nm. Also, the cubic B2 phase of FeCo with a lattice parameter of 0.2857 nm was formed in the annealed films. As a result of oxidation processes, a dispersed phase of manganese oxide also arose after annealing. The temperature dependencies of electrical resistivity of films were measured by the four-point technique upon continuously heating in the high vacuum. Both as-deposited and annealed films clearly revealed a typical ferromagnetic behavior. The as-deposited high-entropy film exhibited the soft magnetic properties while the annealed films could be attributed to hard magnetic materials.

Structure, composition and mechanical properties of reactively sputtered (TiVCrTaW)Nx high-entropy films

Nitride and metallic films multi-element (TiVCrTaW)Nx high-entropy alloy were deposited on silicon wafers by pulse DC magnetron sputtering. The microstructure and mechanical properties of the films prepared with different nitrogen gas flow ratios were studied. The results show that the concentration of nitrogen approached the stoichiometric composition at nitrogen gas ratio RN ≥ 33.3 %. The alloy film deposited with pure argon atmosphere exhibited a BCC structure and a very smooth surface, while an FCC with (111) or (200) preferred orientation and granular surface morphologies was observed in those films prepared with introduction of nitrogen gas. The (TiVCrTaW)Nx films exhibited enhanced hardness upon the addition of nitrogen probably due to the solid-solution strengthening effect and grain refinement. The nitride film achieved the highest hardness and Young’s modulus of 38 GPa and 340 GPa, respectively. The results show that the deposition atmosphere plays a vital rule in the structure and the properties of the (TiVCrTaW)Nx high-entropy films.

Atomic perspective of contact protection in graphene-coated high-entropy films

Covering graphene (Gr) coatings on high-entropy alloy (HEA) films is a promising approach to avoid its contact damage. However, current understanding regarding the underlying strengthening mechanisms of these systems at atomic level remains limited. Here, the contact mechanical behavior and strengthening mechanism of Gr-coated HEA films during nanoindentation were unravelled by means of molecular dynamics (MD) simulations. The results demonstrated that an increase of about 80.3% in indentation hardness of the composites can be endowed by covering a Gr layer, meaning a dramatically enhanced carrying capacity. More importantly, it would be further improved as Gr layers varied from monolayer to trilayer (increases of about 129.3% and 160.2% for the bilayer and trilayer cases, respectively). Moreover, we confirmed that due to the high in-plane stiffness, Gr coatings can effectively decrease the contact stress and inhibit the dislocation nucleation, which facilitated the decreased subsurface damage. Meanwhile, high-density Shockley and Stair-rod dislocations induced by an increase of the actual loading area synergistically promoted a strong strain hardening effect in the composites. It was deemed that the capability of contact protection of HEA films can be further improved after covering Gr coatings which can be ascribed to the high in-plane stiffness of Gr layers coupled with its induced strong strain hardening effect. These findings may contribute to the development and design of Gr-coated HEA composites with better mechanical properties.

Hard and tough AlTiCrNiMo heterostructure high-entropy film deposited by arc ion plating method

Recently the heterostructure high-entropy alloy films (HEF), which normally exhibits better strength and ductility than single-phase HEF, have been paid much attention. In the present study, a heterogeneous-structure AlTiCrNiMo HEF was deposited on TC4 alloys by arc ion plating method. The advanced characterization techniques were utilized to investigate microstructure, mechanical performance and tribological properties of obtained HEF in very systematic manner to provide a comprehensive evaluation. Microstructural examination revealed that as-deposited film contained three types of structures: MoTi spherical compound covered with an amorphous layer and two kinds of disordered solid solutions (the laminar region and dark matrix). Meanwhile, the HEF showed excellent mechanical performance, including a high hardness of ∼11.2 GPa and a low wear rate of ∼1.2 × 10−5 mm3/(N m) against Al2O3 counterpart in open air conditions, which could be owing to the solution strengthening phenomena resulting from the severe-lattice-distortion effect of high-entropy alloy. Additionally, the HEF showed a good resistance to crack damage. The high fracture toughness was achieved because of heterogeneous structure having hard/soft phases present in the film, which exhibited an effective stress-shielding effect and suppressed the propagation of cracks.

Fabrication of high-entropy REBa2Cu3O7−δ thin films by pulsed laser deposition

Thin films of REBa2Cu3O7−δ (RE123, RE: rare earth) having a high-entropy (HE) RE site were successfully fabricated by the pulsed laser deposition method. Solution various RE elements result in increasing configurational entropy of mixing. Critical current density of the HE films exceeds an order of 1.0 MA cm−2 under conditions of T < 20 K and μ 0 H < 7 T. Since the HE effects have a potential to an improvement of irradiation tolerance, the present results encourage further development of HE RE123 superconducting materials used in the environment with high magnetic fields and irradiation, for example in fusion reactors.