Lattice Expansion Research Articles

Application of lattice expansion effect in SrCoO3 based cathodes by Ba doping with elevated electrochemical performances for low-temperature solid oxide fuel cells

Developing excellent-performance cathode materials is an inevitable and challenging obstacle in the process of developing practical solid oxide fuel cells, especially in low temperature range. In this paper, we introduce barium into the premium SrCoO3-based cathodes and research its consequent effect in the oxygen reduction reaction process. It is observed that the barium dopant could expand the lattice, produce more oxygen vacancies and at some extent reduce the thermal expansion coefficient of parent perovskite, which results from the expanded free space for oxygen migration and weakened Co–O bond by Ba doping. The polarization resistances of single cells with Sr1-xBaxCo0.8Sc0.1Nb0.05Ti0.05O3-δ cathodes (x = 0, 0.2 and 0.5, defined as SCSNTi, SB0.2CSNTi and SB0.5CSNTi, correspondingly) are 0.038, 0.025 and 0.016 Ω cm2 at 600 °C, respectively, and corresponding peak power density of 0.852, 1.054 and 1.217 W cm−2. The SB0.5CSNTi cathode is selected and it stably operates for 200 h at 550 °C. And it also exhibits excellent performance when CH4 is used as fuel and good stability for 100 h at 600 °C. First principle calculations prove that the Ba doping effectively reduces the oxygen vacancy formation energy and oxygen migration barrier. This work proves that the lattice expansion effect is an effective strategy for accelerating the oxygen exchange rate and designing high-performance cathode materials.

Cross-examination of photoinitiated carrier and structural dynamics of black phosphorus at elevated fluences.

Revived attention in black phosphorus (bP) has been tremendous in the past decade. While many photoinitiated experiments have been conducted, a cross-examination of bP's photocarrier and structural dynamics is still lacking. In this article, we provide such analysis by examining time-resolved data acquired using optical transient reflectivity and reflection ultrafast electron diffraction, two complementary methods under the same experimental conditions. At elevated excitation fluences, we find that more than 90% of the photoinjected carriers are annihilated within the first picosecond (ps) and transfer their energy to phonons in a nonthermal, anisotropic fashion. Electronically, the remaining carrier density around the band edges induces a significant interaction that leads to an interlayer lattice contraction in a few ps but soon diminishes as a result of the continuing loss of carriers. Structurally, phonon-phonon scattering redistributes the energy in the lattice and results in the generation of out-of-plane coherent acoustic phonons and thermal lattice expansion. Their onset times at ∼6ps are found to be in good agreement. Later, a thermalized quasi-equilibrium state is reached following a period of about 40-50ps. Hence, we propose a picture with five temporal regimes for bP's photodynamics.

Coherent Oscillations in a SrRuO3/BiFeO3 Superlattice.

We investigated the ultrafast dynamics of a SrRuO3/BiFeO3 superlattice grown on a SrTiO3 substrate using a near infrared pump-probe technique at various temperatures. The superlattice exhibits a ferromagnetic order inherited from the SrRuO3 layer. The pump-induced changes in the reflectivity reveal periodic oscillations. We found that the oscillation frequency can be well explained by zone-folded acoustic phonon oscillations, whose dispersion depends on the sound velocity, density, and thickness within the supercell of each constituent layer. It is found that the observed oscillation frequency corresponds to the A1 mode, which suggests that oscillations are excited due to pump-induced expansion of the SrRuO3 layer that absorbs the pump photon. Temperature-dependent measurements reveal significant suppression of the oscillation amplitude in the ferromagnetic state. The suppressed amplitude is proportional to the square of the magnetization, M(T)2. This phenomenon can be attributed to a strong magnetostriction effect of SrRuO3 that suppresses lattice expansion upon pumping.

Densification of low‐density boron carbide by Li doping and its microstructural characterization

AbstractLithium (Li)‐doped boron carbide (B4C) has generated widespread attention for its potential to enhance mechanical properties. Nevertheless, the influence of the Li solid solution on the microstructure and mechanical properties of B4C ceramics remain unclear. In this research, the microstructure of Li‐doped B4C was investigated in meticulous detail. Through X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman spectroscopy analysis, it was confirmed that Li successfully solubilized in B4C at 1 500°C under 50 MPa for an 8 min, resulting in lattice expansion. Further insights from electron energy loss spectroscopy revealed the integration of Li into the crystal lattice and alterations in the C–B–C chains. Furthermore, the Li2O content significantly affected the densification and microstructure of B4C. Relative density increased from 91.2% (B4C) to 99.2% (9 wt.% Li2O–B4C), accompanied by a transition from a few intragranular planar defects to high‐density twins. Mechanical property tests demonstrated that 9 wt.% Li2O–B4C exhibited optimal comprehensive mechanical performance, with a flexural strength of 533 ± 27 MPa, fracture toughness of 3.71 ± 0.29 MPa∙m1/2, hardness of 33.3 ± 0.6 GPa, and a density of just 2.45 g/cm3, surpassing that of pure B4C.

High hydrogen permeability of Pd-Ru-In membranes prepared by electroless co-deposition

In this work, Pd-Ru-In membranes were prepared by electroless co-deposition and characterized by SEM, XRD, XPS, AES and hydrogen permeation test. The results show that defect-free 5–6 μm thick Pd-Ru-In membrane with homogeneous element distribution was successfully prepared. The composition of the membrane is Pd-Ru0.5at%-In1at% (M1) and Pd-Ru0.5at%-In2at% (M2), respectively. The hydrogen permeability of the membrane M2 reaches 1.32 × 10-8 mol·m−1·s−1·Pa−0.5 at 773 K, which is 1.6 times higher than that of a Pd-Ru0.5at% membrane prepared under the same conditions. The addition of the element In leads to a structural evolution of the membrane: the lattice parameters of the Pd-Ru-In membranes increase. This lattice expansion results in an improvement in the hydrogen permeability. Our study provides a useful reference for the fabrication of Pd-Ru-In ternary membranes with high hydrogen permeability.

Strain Engineering of Cd0.5Zn0.5S Nanocrystal for Efficient Photocatalytic Hydrogen Evolution from Wasted Plastic.

The challenge of synthesizing nanocrystal photocatalysts with adjustable lattice strain for effective waste-to-energy conversion is addressed in this study. Cd0.5Zn0.5S (CZS) nanocrystals are synthesized by a simple solvothermal method, regulation of the ratio between N, N-dimethylformamide, and water solvent are shown to provoke expansion and contraction, inducing an adjustable lattice strain ranging from -1.2% to 5.6%. With the hydrolyzed wasted plastic as a sacrificial agent, the 5.6% lattice-strain CZS exhibited a robust hydrogen evolution activity of 1.09mmol m-2h-1 (13.83mmol g-1h-1), 4.5 times that of pristine CZS. Characterizations and density functional theory calculation demonstrated that lattice expansion increases the spatial distance between the valence band maximum and conduction band minimum, thus reducing carrier recombination and promoting charge transfer. Additionally, lattice expansion induces surface S vacancies and adsorbed OH groups, further enhancing redox reactions. This study focuses on the synchronous regulation of crystal structure, charge separation/transport, and surface reactions through lattice strain engineering, which providing a reference for the rational design of new photocatalysts for effective waste-to-energy conversion.

Tailoring the cryogenic magnetism and magnetocaloric effect from Zr substitution in EuTiO3 perovskite

Refrigeration in the liquid helium temperature range provides vital technological support for many scientific frontiers and engineering technologies. The considerable magnetocaloric effect (MCE) makes EuTiO3 a potential candidate for magnetic refrigeration near liquid helium temperature. More interestingly, the magnetic transition from antiferromagnetism to ferromagnetism offers the possibility to tailor the magnetism and improve the MCE of this magnetic system. In this study, the magnetic properties and MCE of EuTi0.875Zr0.125O3 were systematically investigated by first-principles calculation and experiments. The substitution of Zr induces a significant lattice expansion and alters the electronic interactions, leading to a dominance of ferromagnetism in the compound. Remarkable low-field MCE performance has been achieved attributed to the enhanced ferromagnetism and low saturation field. Under the field change of 0–1 T, the maximum magnetic entropy change (−ΔSMmax) and adiabatic temperature change (ΔTadmax) are 17.9 J kg−1 K−1 and 6.1 K, respectively. It is worth noting that the −ΔSMmax of EuTi0.875Zr0.125O3 reaches 10.3 J kg−1 K−1 for a field change of 0–0.5 T, making it one of the best magnetocaloric materials ever reported operating in the liquid helium temperature range.

Modulate the surface charge toward efficient hydrogen evolution reaction: Electronic structure engineering of MoB-Ni3B interface

Rationally regulated the surface electronic structure of catalysts hold the key to enhance the kinetics of hydrogen evolution reaction (HER). Herein, we propose an electronic structure engineering strategy to modulate the surface charge of Ni3B by introducing MoB for high-efficient HER. The MoB-Ni3B interface exhibits characteristic lattice expansion and results in electron modulation between the Ni3B and MoB. Density functional theory calculations further indicate that the introduction of MoB leads to electron enrichment around Ni sites, which further activate Ni sites, weaken the adsorption of hydrogen intermediates and thus facilitate the unfavorable hydrogen desorption, resulting in the Gibbs free adsorption energy closer to zero. As expected, the hierarchical MoB-Ni3B displays an ultra-low overpotential (η10 = 35 and 57 mV for reaching a current density of −10 mA cm−2) in 1.0 M KOH and 0.5 M H2SO4, which is comparable to the commercial Pt catalyst and confirms the positive effect of the modulation of electronic structure on the kinetics and catalytic activity. The effectiveness of the electronic structure engineering strategy is expected to shed light on the construction of more advanced electrocatalysts.

Magnetization reversal and coercivity mechanism in ferrimagnetic M-type hexaferrite by controlling phase evolution

The correlation of phase evolution (annealing at different temperatures) with magnetic properties like magnetization reversal, coercivity mechanism, and energy product in M-type hexaferrite by substituting Sr in place of Ba has been reported in the present article. The Ba1-xSrxFe12O19 (x = 0.0, 0.5, & 1.0) have been prepared by the sol–gel auto-combustion method followed by annealing at different temperatures from 800 °C to 1200 °C. The structural and magnetic properties have been characterized by X-ray diffraction, Field emission scanning electron microscopy, Raman spectroscopy, and Vibrating sample magnetometer. The Rietveld refinement confirms contraction in unit cell parameters by replacing Sr in place of Ba and lattice expansion with increasing annealing temperature. There is no significant effect of substitution on magnetic properties found rather heat treatment affects greatly. The transition from a single domain to multidomain particles and their contribution to initial magnetization curves are analyzed. The differential susceptibility (dM/dH) calculated from room temperature magnetization confirms the existence of a pinning effect during magnetization reversal for samples heat treated below 1200 °C. Secondary phases or grain boundaries are believed to act like pinning centers. This work opens insight into the domain wall motion by microstructure engineering. The coercivity is tuned to 6.09 kOe by controlling the annealing temperature for the Ba1-xSrxFe12O19 (x = 1.0) sample. The maximum energy product (BH)max in the range of 0.94–1.27 MGOe has been achieved.

Strategy to improve magnetic property of sintered (Nd, Ce)–Fe–B magnets: Moderate replacement of cerium with lanthanum

In this work, we proposed a method to enhance the magnetic properties of (Nd, Ce)–Fe–B magnets with Ce/TRE ratios below 25 wt% by introducing a moderate amount of La elements. The segregation behavior of La elements towards grain boundaries (GBs) was utilized to optimize the GB phase structure. Incorporation of La atoms into the main phase induces lattice expansion, leading to an increased formation of Ce3+ ions with enhanced magnetic moments. Comparative analysis with the original magnet (La/Ce = 0 wt%) demonstrates that the magnet with a La/Ce ratio of 10 wt% exhibits improvements of 0.3% in remanence, 12.6% in coercivity, and 0.6% in maximum energy product. These results underscore that the moderate addition of La elements enhances the fluidity of the rare earth-rich phase and optimizes the distribution of lamellar GB, consequently reinforcing the magnetic isolation effect. Furthermore, the promotion of the transformation from Ce4+ to Ce3+ ions contributes to the comprehensive enhancement of the magnetic properties. This research offers a novel strategy for fabricating high-performance and resource-efficient sintered magnets based on LaCe alloys.

Training dependency of neural network interatomic potential for molecular dynamics simulation of Ru-Si-O mixed system

We investigated the training dependency of neural network interatomic potentials for molecular dynamics simulation of a Ru–Si–O mixed system. Our neural network interatomic potential was improved using a data augmentation technique for the training dataset, including data points of reference energies and forces related to reference structures. We demonstrated that the data augmentation technique, focusing on the lattice expansion coefficient of bulk structures in the training dataset, requires moderation to ensure optimal training of the neural network interatomic potential. We found that Ru/SiO2 interfaces were accurately represented using the neural network interatomic potential trained with Ru and SiO2 surfaces in addition to Ru/SiO2 interfaces. In the case of modeling Ru/SiO2 interfaces including unbonded atoms, training the surfaces with unbonded atoms is effective in generalizing the neural network interatomic potential. Our demonstration and finding shed light on the pivotal role of the training dataset on the development of the neural network interatomic potential for the Ru–Si–O mixed system.

High energy storage performance of lead‐free Nb‐modified (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)TiO3 high‐entropy ceramics

AbstractOwing to the intrinsic chemical disorder of microscopic composition, perovskite high‐entropy ceramics exhibit dielectric relaxation behaviors and are favorable for energy storage performance. In this work, (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)(Ti1−xNbx)O3 (BNCBST‐xNb, 0.01 ≤ x ≤ 0.25) ceramics were prepared using a hydrothermal method. The results indicate that Nb doping into BNCBST induces lattice expansion and deepens dielectric relaxation. Moreover, the BNCBST‐xNb ceramics exhibit a great enhancement of electrical breakdown strength (Eb) with Nb content, which results from the reduction of grain size, the increase of resistivity, the decrease of oxygen vacancies, and the enlargement of band gap width. Consequently, the BNCBST‐0.15Nb system presents an outstanding Eb of 497 kV/cm with excellent recoverable energy density (Wrec = 3.85 J/cm3) and efficiency (η = 87.7%), accompanying by the wide temperature stability (Wrec and η vary within ± 9.8% and ± 1.4% at 40–100°C) and fast discharge rate (t0.9 = 88 ns). The significant improvement of Eb and energy storage properties suggest that our research offers an effective strategy for developing lead‐free energy storage ceramics.

Orientation relationship between TiFeH and TiFe phases in AB-type Ti–Fe–V–Ce hydrogen storage alloy

The partially hydrogenated microstructure of an AB-type Ti–Fe–V–Ce hydrogen storage alloy was investigated using scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). For the first time, the formation of the orthorhombic β-TiFeH phase was directly observed by using SEM-EBSD. Lamellar structures consisting of TiFeH and body-centered cubic TiFe phases with a (100)TiFeH∥(100)TiFe habit-plane pair were observed. Pole figure analysis was performed to confirm the orientation relationship between the TiFeH and TiFe phases to be [011](100)TiFeH∥[010](100)TiFe. The formation of TiFeH was characterized by simple lattice expansion with a short-range arrangement of H atoms and surface relief. In addition, unidirectional microcracks along the (100)TiFe planes were observed, presumably owing to the dehydrogenation of the TiFeH phase.

Ionic‐Liquid‐Gating‐Induced Hydrogenation in Epitaxial Strontium Ferrite

AbstractIncorporating hydrogen into complex oxides holds promise for discovering exotic phenomena and novel functionalities by promoting couplings between ion and lattice/charge/spin/orbital degrees of freedom. Here, electrolyte gating‐driven hydrogenation is investigated in epitaxial brownmillerite SrFeO2.5 thin films in which the hydrogenation‐induced lattice distortion is qualitatively different from its counterpart SrCoO2.5. The achievable lattice expansion in hydrogenated SrFeO2.5 is weaker than in SrCoO2.5 and primarily occurs along the normal of the stacked octahedral FeO6 and tetrahedral FeO4 layers. Upon the substitution of Fe with Co, the lattice expansion monotonically increases with increase of Co/Fe ratio, implying an intrinsic difference in accommodating hydrogen between Fe‐ and Co‐based brownmillerites. Moreover, a net magnetic moment in hydrogenated SrFeO2.5 films is observed above room temperature, which gradually weakens with the increase of Co substitution, suggesting a stronger canted magnetism in Fe‐based hydrogenated brownmillerites. This work clarifies the electrolyte gating‐driven hydrogenation mechanisms in brownmillerite SrFeO2.5 epitaxial thin films and those with Co substitution, particularly the deterministic role of Co/Fe ratio in the evolution of structure and properties upon hydrogenation.

Self‐supported VO2 on polydopamine‐derived pyroprotein‐based fibers for ultrastable and flexible aqueous zinc‐ion batteries

AbstractA conventional electrode composite for rechargeable zinc‐ion batteries (ZIBs) includes a binder for strong adhesion between the electrode material and the current collector. However, the introduction of a binder leads to electrochemical inactivity and low electrical conductivity, resulting in the decay of the capacity and a low rate capability. We present a binder‐ and conducting agent‐free VO2 composite electrode using in situ polymerization of dopamine on a flexible current collector of pyroprotein‐based fibers. The as‐fabricated composite electrode was used as a substrate for the direct growth of VO2 as a self‐supported form on polydopamine‐derived pyroprotein‐based fibers (pp‐fibers@VO2(B)). It has a high conductivity and flexible nature as a current collector and moderate binding without conventional binders and conducting agents for the VO2(B) cathode. In addition, their electrochemical mechanism was elucidated. Their energy storage is induced by Zn2+/H+ coinsertion during discharging, which can be confirmed by the lattice expansion, the formation of by‐products including Znx(OTf)y(OH)2x−y·nH2O, and the reduction of V4+ to V3+. Furthermore, the assembled Zn//pp‐fibers@VO2(B) pouch cells have excellent flexibility and stable electrochemical performance under various bending states, showing application possibilities for portable and wearable power sources.

Strain modulation of epitaxial h-BN on sapphire: the role of wrinkle formation for large-area two-dimensional materials.

Strain built-in electronic and optoelectronic devices can influence their properties and lifetime. This effect is particularly significant at the interface between two-dimensional materials and substrates. One such material is epitaxial hexagonal boron nitride (h-BN), which is grown at temperatures often exceeding 1000 °C. Due to the high growth temperature, h-BN based devices operating at room temperature can be strongly affected by strain generated during cooling due to the differences in lattice thermal expansion of h-BN and the substrate. Here, we present results of temperature-dependent Raman studies of the in-plane E2ghighphonon mode in the temperature range of 300-1100 K measured for h-BN grown by metalorganic vapor phase epitaxy. We observe a change, by an order of magnitude, in the rate of the temperature-induced frequency shift for temperatures below 900 K, indicating a strong reduction of the effective h-BN/substrate interaction. We attribute this behavior to the creation of h-BN wrinkles which results in strain relaxation. This interpretation is supported by the observation that no change of layer/substrate interaction and no wrinkles are observed for delaminated h-BN films transferred onto silicon. Our findings demonstrate that wrinkle formation is an inherent process for two-dimensional materials on foreign substrates that has to be understood to allow for the successful engineering of devices based on epitaxially grown van der Waals heterostructures.

High-Humidity-Tolerant Chloride Solid-State Electrolyte for All-Solid-State Lithium Batteries.

Halide solid-state electrolytes (SSEs) hold promise for the commercialization of all-solid-state lithium batteries (ASSLBs); however, the currently cost-effective zirconium-based chloride SSEs suffer from hygroscopic irreversibility, low ionic conductivity, and inadequate thermal stability. Herein, a novel indium-doped zirconium-based chloride is fabricated to satisfy the abovementioned requirements, achieving outstanding-performance ASSLBs at room temperature. Compared to the conventional Li2ZrCl6 and Li3InCl6 SSEs, the hc-Li2+xZr1-xInxCl6 (0.3 ≤ x ≤ 1) possesses higher ionic conductivity (up to 1.4 mS cm-1), and thermal stability (350°C). At the same time, the hc-Li2.8Zr0.2In0.8Cl6 also shows obvious hygroscopic reversibility, where its recovery rate of the ionic conductivity is up to 82.5% after 24-h exposure in the 5% relative humidity followed by heat treatment. Theoretical calculation and experimental results reveal that those advantages are derived from the lattice expansion and the formation of Li3InCl6 ·2H2O hydrates, which can effectively reduce the migration energy barrier of Li ions and offer reversible hydration/dehydration pathway. Finally, an ASSLB, assembled with reheated-Li2.8Zr0.2In0.8Cl6 after humidity exposure, single-crystal LiNi0.8Mn0.1Co0.1O2 and Li-In alloy, exhibits capacity retention of 71% after 500 cycles under 1 C at 25°C. This novel high-humidity-tolerant chloride electrolyte is expected to greatly carry forward the ASSLBs industrialization.

Chemical pressure as an effective tool for tuning the structural disordering and barocaloric efficiency of complex fluorides (NH4)3MF7 (M: Sn, Ti, Ge, Si)

Double fluoride salts (NH4)3M4+F7 (M4+: Sn, Ti, Ge, Si) demonstrate a high efficiency of using chemical pressure as a tool for control and tuning structural ordering/disordering, sensitivity to hydrostatic pressure, successions of the phase transitions, etc and, as a result, for purposeful variation within a wide range of parameters of barocaloric effect (BCE). The conventional and inverse BCEs near the triple points were found on the T − p phase diagrams, combination of which can be used to construct original cooling cycle in narrow temperature and pressure ranges. Reconstructive transformation between two cubic phases, Pm3ˉm↔Pa3ˉ , realized in (NH4)3SnF7 at atmospheric pressure and in (NH4)3TiF7 at p> 0.4 GPa are characterized by rather low thermal hysteresis, δT0 = 1 K, and a great entropy change, ΔSBCE = 110–152 J (kg · K)−1, depending on the size of the central atom. At above 300–350 K, a contribution to BCE associated with the regular thermal expansion of the crystal lattice becomes comparable to entropy and temperature changes under pressure in the region of the phase transitions. An analysis of the absolute, relative and integral barocaloric characteristics of (NH4)3M4+F7 compounds showed their high competitiveness with respect to other barocaloric materials considered as promising solid-state refrigerants.

Quasi‐in situ Observation of MnO2 Nanorods by Electrochemical Transmission Electron Microscopy for Oxygen Reduction Reaction Process

Understanding the electrode materials’ surface is of fundamental importance for catalytic studies as most electrochemical reactions take place there. Although several operando techniques have been used to monitor the electrocatalytic process, real‐time imaging techniques for observing the surface change on electrode materials are still a challenge and limited to a few stable catalytic systems. Herein, the quasi‐in situ electrochemical transmission electron microscopy (TEM) was carried out to track the morphological and local structure evolution during the oxygen reduction reaction (ORR) on manganese dioxide (MnO2) for the first time. The α‐MnO2 nanorods exhibit comparable ORR electrocatalytic activity (half‐wave potential, E1/2: 0.83 vs. 0.85 V vs. RHE; diffusion‐limiting current density, Jd: −5.46 vs. −5.52 mA cm−2) and better methanol tolerance than Pt/C. An electrochemical TEM chip assembled with a three‐electrode system was used to perform the electrochemical experiments similar to typical testing procedures. The ex situ and quasi‐in situ TEM images consistently showed that MnO2 nanorods had undergone surface roughening, and lattice expansion with 0.97% and 1.97% in the a and c‐axis, respectively as ORR proceeded. The quasi‐in situ electrochemical TEM fills the gap between ex situ characterization and operando spectroscopies and deepens the mechanistic understanding of electrocatalytic processes.

Structural and mechanical responses of (ZrTiNbTa)C4 and ZrC ceramics under energetic He-ions irradiation

High entropy ceramics are potential structural materials for advanced reactor concepts where numerous helium atoms would be produced due to the (n, α) nuclear transmutation reaction. However, the irradiation behaviors of high entropy ceramics are not well understood until now. In present work, the responses of high entropy (ZrTiNbTa)C4 and its binary constituent ZrC ceramics to energetic He-ions irradiation have been studied. X-ray diffraction analysis showed that He-ions irradiation resulted in peak shift and broadening of diffraction peaks in both (ZrTiNbTa)C4 and ZrC, which denotes lattice expansion and structural damages induced by the irradiation. Transmission electron microscope observation revealed that spherical helium bubbles distribute uniformly in the grain interiors of (ZrTiNbTa)C4 while “string-like” bubbles with a preferred orientation are observed in ZrC grains. Nanoindentation characterization gives that the irradiation induced hardening of (ZrTiNbTa)C4 is less definite than that of ZrC. The irradiation mechanisms of high entropy ceramics have been discussed.