Large Radius Research Articles

Enhancing the Cycling and Rate Performance of NaNi1/3Fe1/3Mn1/3O2 Cathodes by La/Al Codoping.

O3-type layered oxides hold significant promise as the material for cathodes in sodium-ion batteries for their favorable electrochemical properties, while irreversible structural degradation and harmful phase transitions during cyclic operation limit the practical application of these materials. In this work, we proposed a La3+/Al3+ codoping strategy in O3-Na(Ni1/3Mn1/3Fe1/3)O2 cathode materials and found that batteries with the Na (Ni1/3Mn1/3Fe1/3)0.998La0.001Al0.001O2 (NFM-La/Al) cathodes exhibited not only promoted capacity from 135.80 to 170.42 mAh g-1 at 0.2 C but also significantly enhanced cycling stability, with a 10% improvement in capacity retention compared with NFM cathodes after 300 cycles. Particularly, their rate performance was significantly improved as well. XRD and XPS tests indicated that La could expand the c-axis of NFM due to its larger ionic radius and thus significantly increased Na+ ion diffusion efficiency, and in addition, Al doping could effectively increase the content of Ni2+ and Mn4+ and thus greatly alleviated the negative Jahn-Teller effect caused by Mn3+. Moreover, consistent with XRD analyses, DFT calculations further substantiated the effectiveness of the La/Al codoping strategy by demonstrating the detailed atom substitution mechanism in the NFM crystal lattice. The boosted structure stability and Na+ diffusion kinetics may enhance the potential for practical applications of O3-type oxide cathodes.

Coupled influence of bypass ratio and throttling strength on characteristics and stall margin of variable-cycle fan

Three-dimensional numerical simulations of a first-stage fan in a variable-cycle engine (VCE) were performed to reveal the characteristics of the fan under different working conditions and the factors influencing them. The results indicated that several combinations of outer and inner bypass throttling could be used to achieve the same bypass ratio. To the best of our knowledge, this study is the first to establish the characteristic curves, which are dependent on the bypass ratio and throttling of the VCE fan. Consequently, the most suitable method of reducing the bypass ratio while ensuring a sufficient stall margin for the fan was to increase the outer bypass throttling and reduce the inner bypass throttling. Moreover, the only difference between the aerodynamic characteristic curves of the VCE fan for various bypass ratios at the same speed was the stall margin. An analysis of the flow field near the stall point revealed that the fan exhibited flow separation over an area with a large radius. Consequently, based on this flow separation, the reasons for the fan having different stall margins at different bypass ratios were explained. Furthermore, the axial position of the splitter was the primary factor affecting the throttling strength, whereas the radial position of the splitter determined the range of influence of throttling.

Organic molecular intercalation regulated hydrated vanadate cathodes with improved electrochemical properties and fast kinetics for aqueous zinc-ion batteries

Due to the large hydrated zinc ion radius resulting from the stable solvation structure with six water molecules in electrolyte, the interlayer spacing of most vanadium-based materials fails to meet the requirements for efficient insertion and extraction of Zn2+. Therefore, it is crucial to optimize and reconstruct the VO layer structure in order to achieve rapid and stable zinc storage. In this paper, composites of phenylalanine methyl ester (PM) inserted hydrated V2O5 (PMVO) are prepared using a one-step hydrothermal method. With the increase of PM insertion, the electrochemical properties initially exhibit enhancement followed by subsequent decline. Notably, PMVO-1.6 presents exceptional electrochemical performance, including a high capacity of 464 mAh g−1 at 0.1 A g−1, excellent rate capability with 220 mAh g−1 at 7 A g−1, and superior cycling stability with 97.5 % capacity retention after 1000 cycles at 4 A g−1. The incorporation of PM not only serves as stable structural pillars, but also reduces the solubilization of vanadium, facilitates the diffusion kinetics of hydrated zinc ions, and enhances the surface pseudo-capacitance effect.

Synthesis pathways of (HfZrTiCe/La/Y)O2-x nanoparticles via benzyl alcohol route at critical temperature

The controllable synthesis of high-entropy fluorite oxide (HEO) having large ionic radius mismatch remains a challenging due to poor understanding on nucleation. The (HfZrTiLn)-5HEO nanoparticles with 15 % ionic radius mismatch were synthesized via benzyl alcohol route at 220 °C-5 min in presence of PtCl4 and Fe(acac)3, exhibiting novel optical, electrical and magnetic properties. Nucleation pathways of the 5HEO at the critical temperature were elucidated by using a comparison study of conventional heating and microwave irradiation heating. Consistency of XRD patterns and STEM-EDX observation indicate that the resultant Hf-OBn monomers acted as the nucleation center of the 5HEO, determined by diffusion kinetics. The nucleation rate depended on the metal monomers assembly and esterification reaction, which was accelerated by water vapor pressure produced in-situ by 0.5×10−4mol/l PtCl4 catalyst. The Fe-metal organic cages derived from 1.5×10−4mol/l Fe(acac)3 additive served as the structure stabilizer of Zr/Ti monomers, and prevented early hydrothermal reaction route.

Analytical solutions of the kinetic equation for rounded spirals in effectively isotropic systems

A method for finding analytical solutions to the Cabrera and Levine differential equation is proposed for the case of the spiral formation on a screw dislocation when there is no difference between the growth and evaporation of a crystal. The method is based on finding asymptotic solutions for small spiral angles, exact solutions in the interval of dimensionless spiral radii equal and exceeding unity, and asymptotic solutions for large radii. Then, the method of matching the obtained solutions and their derivatives by dimensionless radius is used for two radius values determined from the problem conditions. In the particular case, for angular velocity ω1=0.33, the exact solution is the result of matching the asymptotic solution of the original equation for small spiral angles, the exact solution in the interval of dimensionless spiral radii equal and exceeding unity, and the asymptotic solution for large radii. For large spiral radii, the asymptotic solution is the general one of the second kind Abel equation. Analysis of the obtained solution showed that the spiral pitch is not constant and equal to 19, but monotonically decreases with increasing spiral radius.

The aeroelastic stability characteristics of a ring-stiffened conical three-layered sandwich shell with an FG auxetic honeycomb core utilizing zig-zag shell theory

This paper is devoted to the supersonic flutter analysis of a ring-stiffened conical three-layered sandwich shell consisting of an auxetic honeycomb (AH) core fabricated from functionally graded material (FGM). The face sheets are manufactured of FGM as well in which the volume fraction of the ceramic increases from zero at the inner surface to one at the outer surface based on a power-law function. The sandwich shell is mathematically modeled based on the Murakami's zig-zag shell theory and the aerodynamic pressure is modeled utilizing piston theory. The derivation of governing equations along with compatibility and boundary conditions are performed using Hamilton's principle and are solved through a semi-analytical solution consisting of an exact solution in the circumferential direction followed by an approximate solution in the meridional direction. The flutter boundaries are attained to investigate the variations of the natural frequencies and damping ratios to find the critical aerodynamic pressure (CAP). The impacts of several factors on the CAP are examined such as the power-law index, geometric characteristics of the cells in the FGAH, thickness of the honeycomb core, location of the ring, and boundary conditions. It is observed that an optimal location can be found for the ring support somewhere between the middle length and large radius of a conical shell that provides the best aeroelastic stability.

Mechanisms Underlying Rail Corrugation on Tracks Equipped with Cologne-Egg Fasteners

Rail corrugation is the most common type of abnormal damage in subway track systems, and there is currently no unified theory that fully explains this specific wear phenomenon. In this research, a coupled rigid–flexible dynamics model and a multi-rigid body dynamics model was established, accounting for the effects of fastener systems, to study severe rail corrugation on tracks equipped with Cologne-egg fastener (CE fastener). The low vertical support stiffness of CE fasteners, combined with heavy train loads, leads to the “soft mud effect.” This effect causes the creep force between the wheel and rail to become saturated more easily, which is the root cause of frequent rail corrugation on both tangent tracks and curved tracks with large radii. Additionally, drawing on the theory of friction-driven self-excitation vibration, a finite element model of a wheelset–rails system with CE fasteners was established to study the unstable vibration caused by wheel–rail sliding. An increased friction coefficient increases the tendency toward unstable vibration in a wheelset–CE fastener–rail system. Three types of composite under-rail vibration absorbers were designed to suppress rail corrugation, with the continuous-type absorber demonstrating the best suppressive effect.

Radiation model and thermal characteristics of OLED glass substrate using electric heating tube

Glass substrate (GS) heating is a fundamental but significant technology for organic light emitting diode (OLED), which is critical to OLED displaying quality and efficiency. A rapid and reliable theoretical model is intensely demanded to guide practical system design, simulation analysis and experimental research for GS heating, but present radiative models are improper or inconvenient. Therefore, this paper establishes a new and direct calculation model with the addition of correctional coefficient 0.5 to blackbody radiation power of electric heating tube (EHT) and the proposal of comprehensive angle coefficient X, which can solve single and multi-source radiation problems theoretically. The simulation and experiment are both conducted for comparison analysis. The temperature errors of theory and simulation for multi EHTs are all within 1 % when compared with experimental results, which well validates the reliability and accuracy of theoretical and simulation models. Large EHT radius r, small distance L between EHT and GS, and suitable EHT number n are suggested, which benefits to the improvement of radiation heating and temperature uniformity of GS. It is hoped that this study can provide a useful tool on thermal radiation analysis and also a valuable promotion for practical OLED heating technology.

Modeling Compact Object Mergers GW190814 and GW200210 and Other Self-bound Compact Stars with Dark Matter Induced by Gravitational Decoupling and Its Significance to the Mass Gap

We present a rigorous study of compact objects within f(Q) gravity where electrical fields and dark matter are studied and provide novel mass–radius relations with models falling in the mass gap of the events GW190814 and GW200210. After formulating the basic equations and finding their relevant solutions, we impose the boundary conditions on the system under treatment. The decoupled solution for the strange stellar model with the dark matter density profile is obtained. The distribution patterns of the effective energy density and the radial as well as the tangential pressure and anisotropy in the system are intensively examined. The stability properties of the stellar configuration and the influence of dark matter are studied. The recent observations of supermassive compact star candidates such as PSR J1614–2230 and PSR J0952–0607 with observed masses greater than or equal to 2 M ⊙ have been employed in our study. Interestingly, the present study predicts the constraints on mass–radius measurements of the observed stars satisfying the equation of state based on the MIT bag model and employing the condition of mimicking, i.e., ρ θ = χ1ρPI in f(Q) gravity. Our graphical results exhibit that for a particular M–R curve with fixed values of the parameters, neutron stars having mass less than M max exist with larger radii within the context of the f(Q) formalism.

Influence of pressure anisotropy on mass-radius relation and stability of millisecond pulsars in f(Q) gravity

In this study we explore the astrophysical implications of pressure anisotropy on the physical characteristics of millisecond pulsars within the framework of f(Q) gravity, in particular f(Q) = - α Q - β,where α and β are constants. Starting off with the field equations for anisotropic matter configurations, we adopt the physically salient Durgapal-Fuloria ansatz together with a well-motivated anisotropic factor for the interior matter distribution. This leads to a nonlinear second order differential equation which is integrated to give the complete gravitational and thermodynamical properties of the stellar object. The resulting model is subjected to rigorous tests to ensure that it qualifies as a physically viable compact object within the f(Q)-gravity framework. We study in detail the impact of anisotropy on the mass, radius and stability of the star. Our analyses indicate that our models are well-behaved, singularity-free and can account for the existence of a wide range of observed pulsars with masses ranging from 2.08 to 2.67 M ⊙, with the upper value being in the so-called mass gap regime observed in gravitational events such as GW190814. A comparison of the so-called Symmetric Teleparallel Equivalent to GR (STEGR) models with classical General Relativity (GR) models reveal that the anisotropy parameter and the sign of β impact on the predicted radii of pulsars. In particular, STEGR models have larger radii than their GR counterparts.

Impact of Slim Linear Echoendoscope on the Practice of EUS.

Standard linear echoendoscopes have a large distal tip and bending radius, which can preclude adequate examination in some patients. We examined the impact of having available slim linear echoendoscopes (SLE) on our endoscopic ultrasound (EUS) practice. As a quality improvement measure, data on the need for the use of SLE were documented in 2000 consecutive procedures performed over a 10-month period from February to November 2022. When examination using a standard size echoendoscope failed due to technical limitations, the procedure was reattempted in the same session using a SLE. The main outcome was the impact of SLE, which was defined as the establishment of a new diagnosis or if findings altered treatment plan. A complete EUS examination failed in 23 of 2000 procedures (1.15%, 95% CI, 0.73-1.72%) performed using standard size echoendoscope (14 male, median age 73y [IQR 66 to 79]). The examination was technically successful when using SLE in 22 of 23 (95.6%) patients. SLE impacted clinical management in all 22 patients (100%) by establishing tissue diagnosis in 19 and/or altering subsequent treatment plan in 5. Adverse event of transient hypoxia was observed in one patient (4.3%). A very experienced EUS team required SLE in 1.1% of consecutive examinations. Our findings suggest that when used, 95% of patients benefitted as it had a significant impact on their clinical management.

Jet formation in post-AGB binaries

Context. Jets are launched from many classes of astrophysical objects, including post-asymptotic giant branch (post-AGB) binaries with a circumbinary disc. Despite dozens of detections, the formation of these post-AGB binary jets and their connection to the inter-component interactions in their host systems remains poorly understood. Aims. Building upon the previous paper in this series, we consider cold self-similar magnetohydrodynamic (MHD) disc wind solutions to describe jets that are launched from the circumcompanion accretion discs in post-AGB binaries. Resulting predictions are matched to observations. This both tests the physical validity of the MHD disc wind paradigm and reveals the accretion disc properties. Methods. Five MHD solutions are used as input to synthesise spectral time-series of the Hα line for five different post-AGB binaries. A fitting routine over the remaining model parameters is developed to find the disc wind models that best fit the observed time-series. Results. Many of the time-series’ properties are reproduced well by the models, though systematic mismatches, such as overestimated rotation, remain. Four targets imply accretion discs that reach close to the secondary’s stellar surface, while one is fitted with an unrealistically large inner radius at ≳20 stellar radii. Some fits imply inner disc temperatures over 10 000 K, seemingly discrepant with a previous observational estimate from H band interferometry. This estimate is, however, shown to be biased. Fitted mass-accretion rates range from ∼10−6 − 10−3 M⊙/yr. Relative to the jets launched from young stellar objects (YSOs), all targets prefer winds with higher ejection efficiencies, lower magnetizations and thicker discs. Conclusions. Our models show that current cold MHD disc wind solutions can explain many of the jet-related Hα features seen in post-AGB binaries, though systematic discrepancies remain. This includes, but is not limited to, overestimated rotation and underestimated post-AGB circumbinary disc lifetimes. The consideration of thicker discs and the inclusion of irradiation from the post-AGB primary, leading to warm magnetothermal wind launching, might alleviate these.

Coherent Inverse Compton Scattering in Fast Radio Bursts Revisited

Growing observations of temporal, spectral, and polarization properties of fast radio bursts (FRBs) indicate that the radio emission of the majority of bursts is likely produced inside the magnetosphere of its central engine, likely a magnetar. We revisit the idea that FRBs are generated via coherent inverse Compton scattering (ICS) off low-frequency X-mode electromagnetic waves (fast magnetosonic waves) by bunches at a distance of a few hundred times the magnetar radius. The following findings are revealed: (1) Crustal oscillations during a flaring event would excite kHz Alfvén waves. Fast magnetosonic waves with essentially the same frequency can be generated directly or be converted from Alfvén waves at a large radius, with an amplitude large enough to power FRBs via the ICS process. (2) The cross section increases rapidly with radius and significant ICS can occur at r ≳ 100R ⋆ with emission power much greater than the curvature radiation power but still in the linear scattering regime. (3) The low-frequency fast magnetosonic waves naturally redistribute a fluctuating relativistic plasma in the charge-depleted region to form bunches with the right size to power FRBs. (4) The required bunch net charge density can be sub-Goldreich–Julian, which allows a strong parallel electric field to accelerate the charges, maintain the bunches, and continuously power FRB emission. (5) This model can account for a wide range of observed properties of repeating FRB bursts, including high degrees of linear and circular polarization and narrow spectra as observed in many bursts from repeating FRB sources.

The correlation between dip width and peak flux in Cir X-1

In this work we analyzed the long-term X-ray variation of Cir X-1 and its spectra. The dip width and the peak flux after periastron are obtained. Our findings show a negative correlation between the dip width and the peak flux. A new scenario is introduced to explain the correlation. The disk height is higher at a larger radius in the standard model. When the neutron star (NS) moves away from periastron, the contraction of the equipotential surface causes the height of the outer disk to increase significantly. It blocks the X-ray emission near the NS. Subsequently, the height of the outer disk gradually decreases due to the viscosity. The viscous timescale is inversely proportional to the height of the disk, and the height of the outer disk is proportional to the mass transferred from the companion near periastron, thus the peak flux. Consequently, the duration of the obscuring, corresponding to the dip width, is inversely proportional to the peak flux. Moreover, we introduce a new ephemeris MJD (N) = 43075.0+16.5843N-4.778 N^2$ based on the dip-in phases (ingress phase of the dip).

Tailoring structural and optical properties of Ti1-xMxO2 (M = Fe, Co, Ni, Cu, and Zn) nanoparticles for enhanced antimicrobial activity: a sol-gel synthesis study

Titanium dioxide (TiO2) nanoparticles possess intriguing properties and have been extensively utilized in medical applications due to their exceptional antimicrobial characteristics. The antimicrobial efficacy can be heightened by altering the structural morphology, size, and optical properties through the introduction of transition metal ions (M: Fe, Co, Ni, Cu, and Zn) with a concentration of x = 0.02 into TiO2, thereby producing Ti1 -xMxO2 powder via the sol-gel method at a sintering temperature ranging from 500 °C to 600 °C. The morphological characteristics of Ti1 - xMxO2 were analyzed using FT-IR, UV-DRS, XRD, TGA, BET, and SEM-EDAX techniques. Substituting M-doped TiO2 at a sintering temperature of 500 °C results in all doping ions yielding the Ti1 -xMxO2 anatase phase. Conversely, at 600 °C, the doping ions M: Cu, Co, Zn exhibit a tendency to substitute the TiO2 structure, destabilizing the anatase phase and leading to the formation of an anatase-rutile dual phase with larger crystal size. At elevated temperatures, ions with larger radii than Ti (0.61), namely Cu (0.73), Co (0.75), and Zn (0.74), tend to be substituted, thereby altering the structure of TiO2. The antimicrobial efficacy, evaluated based on the inhibition zone, demonstrates that Ti1 -xMxO2 effectively inhibits the cellular activity of Salmonella typhimurium (Gram -) and Staphylococcus aureus (Gram +) bacteria compared to TiO2.

Potential Impacts of Future Climate Change on Super-Typhoons in the Western North Pacific: Cloud-Resolving Case Studies Using Pseudo-Global Warming Experiments

Potential impacts of projected long-term climate change toward the end of the 21st century on rainfall and peak intensity of six super-typhoons in the western North Pacific (WNP) are assessed using a cloud-resolving model (CRM) and the pseudo-global warming (PGW) method, under two representative concentration pathway (RCP) emission scenarios of RCP4.5 and RCP8.5. Linear long-term trends in June–October are calculated from 38 Coupled Model Intercomparison Project phase 5 (CMIP5) models from 1981–2000 to 2081–2100, with warmings of about 3 °C in sea surface temperature, 4 °C in air temperature in the lower troposphere, and increases of 20% in moisture in RCP8.5. The changes in RCP4.5 are about half the amounts. For each typhoon, three experiments are carried out: a control run (CTL) using analysis data as initial and boundary conditions (IC/BCs), and two future runs with the trend added to the IC/BCs, one for RCP4.5 and the other for RCP8.5, respectively. Their results are compared for potential impacts of climate change. In future scenarios, all six typhoons produce more rain rather consistently, by around 10% in RCP4.5 and 20% in RCP8.5 inside 200–250 km from the center, with increased variability toward larger radii. Such increases are tested to be highly significant and can be largely explained by the increased moisture and water vapor convergence in future scenarios. However, using this method, the results on peak intensity are mixed and inconsistent, with the majority of cases becoming somewhat weaker in future runs. It is believed that in the procedure to determine the best initial time for CTL, which yielded the strongest TC, often within a few hPa in minimum central sea-level pressure to the best track data, an advantage was introduced to the CTL unintentionally. Once the long-term trends were added in future runs, the environment of the storm was altered and became not as favorable for subsequent intensification. Thus, the PGW approach may have some bias in assessing the peak intensity of such super-typhoon cases, and caution should be practiced.

Influences of Background Rotation on Secondary Eyewall Formation of Tropical Cyclones in Idealized f‐Plane Simulations

AbstractThis study investigates the background rotational influences on the secondary eyewall formation (SEF) in tropical cyclones (TCs) in quiescent f‐plane environments. For given initial structures, simulated vortices tend to experience earlier SEF at lower latitudes. Yet the size of the secondary eyewall does not change monotonically with the latitudes. Specifically, ∼20°N provides the optimal amount of background rotation for the largest secondary eyewall size without considering other environmental forcings. Different background rotation rates affect SEF mainly by modulating the outer‐core convection as well as the wind structures. Specifically, the lower rotation rate causes more outer‐core surface fluxes, thus facilitating the outer rainbands (ORBs) at larger radii. Yet the secondary eyewall does not necessarily form at larger radii at lower latitudes since the transition from the ORBs to secondary eyewall is localized in a region of boundary layer (BL) convergence preceded by accelerated tangential winds. Budget analysis reveals that the differences in the acceleration of outer‐core tangential winds among vortices at different latitudes are dominated by the radial flux of absolute vorticity. Due to the non‐uniform influences of background rotation on the BL inflow and absolute vorticity, the most efficient spin‐up of outer‐core tangential winds is achieved at a medium latitude of 20°N, which leads up to SEF at the largest radii. By comparison, for TCs at lower (higher) latitudes, the lower outer‐core absolute vorticity (radial inflow) limits the acceleration of outer‐core tangential winds, thus placing SEF at smaller radii.

Accurate and Model-independent Radius Determination of Single FGK and M Dwarfs Using Gaia DR3 Data

Measuring fundamental stellar parameters is key to fully comprehending the evolution of stars. However, current theoretical models overpredict effective temperatures, and underpredict radii, compared to observations of K and M dwarfs (radius inflation problem). In this work, we have developed a model-independent method to infer precise radii of single FGK and M dwarfs using Gaia DR3 parallaxes and photometry, and used it to study the radius inflation problem. We calibrated nine surface brightness–color relations for the three Gaia magnitudes and colors using a sample of stars with angular diameter measurements. We achieved an accuracy of 4% in our angular diameter estimations, which Gaia’s parallaxes allow us to convert to physical radii. We validated our method by comparing our radius measurements with literature samples and the Gaia DR3 catalog, which confirmed the accuracy of our method and revealed systematic offsets in the Gaia measurements. Moreover, we used a sample with measured Hα equivalent width (Hα EW), a magnetic activity indicator, to study the radius inflation problem. We demonstrated that active stars have larger radii than inactive stars, showing that radius inflation is correlated with magnetic activity. We found a correlation between the radius inflation of active stars and Hα EW for the mass bin 0.5 < M[M ⊙] ≤ 0.6, but we found no correlation for lower masses. This could be due to lack of precision in our radius estimation or a physical reason. Radius measurements with smaller uncertainties are necessary to distinguish between the two scenarios.

Fate of initially bound timelike geodesics in spherical boson stars

Boson stars are horizonless compact objects and they could possess novel geodesic orbits under the equilibrium assumption, which differ from those in black hole backgrounds. However, unstable boson stars may collapse into black holes or migrate to stable states, resulting in an inability to maintain the initially bound geodesic orbits within the backgrounds of unstable boson stars. To elucidate the fate of initially bound geodesic orbits in boson stars, we present a study of geodesics within the spherical space times of stable, collapsing, and migrating boson stars. We focus on timelike geodesics that are initially circular or reciprocating. We verify that orbits initially bound within a stable boson star persist in their bound states. For a collapsing boson star, we show that orbits initially bound and reciprocating finally either become unbound or plunge into the newly formed black hole, depending on their initial maximal radii. For initially circular geodesics, we have discovered the existence of a critical radius. Orbits with radii below this critical value are found to plunge into the newly formed black hole, whereas those with radii larger than the critical radius continue to orbit around the vicinity of the newly formed black hole, exhibiting nonzero eccentricities. For the migrating case, a black hole does not form. In this case, the reciprocating orbits span a wider radial range. For initially circular geodesics, orbits with small radii become unbound, and orbits with large radii remain bound with nonvanishing eccentricities. This geodesic study provides an approach to investigating the gravitational collapse and migration of boson stars. Published by the American Physical Society 2024

Unraveling the corrosion mechanism of high entropy Yb2(Zr0.2Hf0.2Ti0.2Sn0.2Ce0.2)2O7 under CaO-MgO-Al2O3-SiO2 (CMAS) attack

The infiltration depth of Yb2(Zr0.2Hf0.2Ti0.2Sn0.2Ce0.2)2O7 - referred to as Yb₂(5HE)₂O₇ - is only 25 % of Yb2Zr2O7 after corroding for 24 h. The enhanced CaO-MgO-Al2O3-SiO2 (CMAS) resistance of Yb2(5HE)2O7 is ascribed to the formation of a dense and stable sealing layer at the infiltration front, primarily consisting of apatite enveloping large fluorite grains. The rapid precipitation of apatite is promoted by large ionic radius and the increased RE concentration due to the rapid dissolution of Ce. This facilitates rapid saturation of RE ions at the grain boundaries, leading to the precipitation of apatite around fluorite. Additionally, the large Ce enhances the driving force for apatite crystallization.