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This study investigates the influence of separate and combined addition of 5 vol.% TiC and/or WC on the isothermal oxidation behaviour of ZrB2–20 vol.% SiC composites consolidated by a spark plasma sintering route. The oxidation performance of the composites was evaluated in the temperature range of 1500–1600 °C in air for up to 4 h. Following oxidation, the samples were subjected to a detailed characterization of the microstructure, micro-composition, phase aggregate, and oxide scale growth kinetics. The thermodynamic feasibility of probable reactions and the phase stability of Zr–B–O, Zr–Si–O, Ti–B–O, Ti–C–O, Ti–W–O, and W–C–O systems were examined by dedicated software. While addition of TiC or WC was found to result in protective oxide scale formation, the highest oxidation resistance in terms of reduced mass gain and oxide layer thickness was offered by ZrB2–20SiC–2.5TiC–2.5WC (vol.%) composite at 1500–1600 °C in air. [ABSTRACT FROM AUTHOR]

My purpose in this paper is to find the underlying electronic cause of the observed thermodynamic stabilisation of δ-phase plutonium. I present a simple model demonstrating that the valence fluctuations found in δ-phase are essential for stabilising this phase. I make two explicit comparisons of the temperature dependencies of the available heat capacity data: one of α-phase Pu versus δ-phase Pu, and the other of α-Pu versus an artificial δ-phase model which includes only lattice vibrations and a free-electron term. These comparisons strongly suggest that delta phase is stabilised – both at high and low temperature – by the entropy of the valence fluctuations which are present in this phase. [ABSTRACT FROM AUTHOR]

In this study, Gd2O3 and Yb2O3 co-doped YSZ (GYYSZ) ceramic coatings were prepared via atmospheric plasma spraying (APS). The GYYSZ ceramic coatings were subjected to heat treatment at different temperatures for 5 h to analyze their high-temperature phase stability and sintering resistance. The thermophysical properties of GYYSZ, YSZ, and composite coatings were compared. Three types of thermal barrier coatings (TBCs) were designed: GYYSZ (TBC-1), YSZ/GYYSZ (TBC-2), and YSZ/Composite/GYYSZ (TBC-3). The failure mechanisms of these three TBCs were investigated. The results indicate that both the powder and the sprayed GYYSZ primarily maintain a homogeneous cubic phase c-ZrO2, remaining stable at 1500 °C after annealing. The sintering and densification of the coatings are influenced by the annealing temperature; higher temperatures lead to faster sintering rates. At 1500 °C, the grain size and porosity of GYYSZ are 4.66 μm and 9.9%, respectively. At 1000 °C, the thermal conductivity of GYYSZ is 1.35 W·m−1 K−1, which is 44% lower than that of YSZ. The thermal conductivity of the composite material remains between 1.79 W·m−1 K−1 and 1.99 W·m−1 K−1 from room temperature to 1000 °C, positioned between GYYSZ and YSZ. In the TBC thermal shock water quenching experiment, TBC-3 demonstrated an exceptionally long thermal shock lifetime of 246.3 cycles, which is 5.8 times that of TBC-1 and 1.8 times that of TBC-2. The gradient coating structure effectively reduces the thermal mismatch stress between layers, while the dense surface microcracks provide a certain toughening effect. Failure analysis of the TBC reveals that TBC-3 exhibits a mixed failure mode characterized by both spallation and localized peeling. The ultimate failure was attributed to the propagation of transverse cracks during the final stage of water quenching, which led to the eventual spallation of the ceramic blocks. [ABSTRACT FROM AUTHOR]

All‐inorganic triiodide cesium lead (CsPbI3) exhibits huge potential in perovskite solar cells (PSCs). However, the high‐temperature crystallization process (≈340 or 180 °C) limits their further development, especially in flexible PSCs. Here, a Cs─I bond weakening approach is proposed to realize the low‐temperature crystallization of CsPbI3 by introducing organic sulfonate of 1‐propylsulfonate‐3‐methylimidazolium chloride (SMCl). SMCl can strongly interact with CsI and weaken the Cs─I bond to dissociate free I− ions for the effective transition of initial PbI2 to [PbI6]4−, which greatly decreases the crystallization temperature of black CsPbI3 to 90 °C. As a result, flexible PSCs are realized with efficiency of 13.86%, which is the highest efficiency of flexible CsPbI3 devices. Besides, SMCl will also help to release the tensile strain and stabilize CsPbI3 phase, leading to good thermal and mechanical stability. Almost no efficiency loss is observed in flexible PSCs after 36000 bending cycles with a curvature radius of 5 mm. [ABSTRACT FROM AUTHOR]

Coal gangues i a solid waste during the coal mining process and the accumulation of coal gangue will harm the environment. Therefore, solid waste utilization of coal gangue is required to reduce the environmental damage. In this paper, cordierite ceramics are successfully prepared via a solid‐phase sintering using coal gangue, Al2O3, and MgO as raw materials. The effects of sintering temperatures on the microstructures, phase stability, and thermal properties of ceramics are investigated. The results show that the properties of cordierites prepared at 1200°C are close to those of prepared by the traditional method, and the synthesized ceramics have thermal expansion coefficients (TECs) and conductivity of 4.1–10−6 K−1 and 1.72 W·m−1 K−1 at 900°C, respectively. The sample prepared at 1200°C has good wear resistance (η) with a wear resistance coefficient of 0.507, and an excellent thermal shock resistance, which can withstand 15 times of cold and hot shocks at 1100°C without any cracks on the surface. This study systematically elucidates the thermal/mechanical properties of the synthesized cordierite, and the feasibility of using coal gangue as raw materials prepared cordierite ceramics as refractory materials. This work presents an effective solution to mitigate the challenge of coal gangue disposal. [ABSTRACT FROM AUTHOR]

(Mg 0.2 Al 0.2 Ce 0.2 Y 0.2 Zr 0.2)O 1.6 high entropy ceramics powders have been prepared by co-precipitation method with two calcination temperatures (1000 °C and 1200 °C). The microstructure, phase composition and phase stability after repeated calcination at 1400 °C with various times of the powders have been investigated. The powder calcined at 1200 °C has the better crystallinity and the stronger diffraction peak of t-ZrO 2 phase at room temperature. The existence of Ce4+ and Y3+ with large radius in the ZrO 2 lattice can enhance the tetragonality of the powders. The Mg2+ and Al3+ with small radii can exist in the lattice gap of ZrO 2 or replace the position of Zr4+, causing lattice contraction, offsetting the lattice expansion which caused by Ce4+ and Y3+, and reducing the negative effects induced by the large ion doping. Thus, (Mg 0.2 Al 0.2 Ce 0.2 Y 0.2 Zr 0.2)O 1.6 has a good phase stability after repeated calcination at 1400 °C for 80h. [ABSTRACT FROM AUTHOR]

The emergence of multi‐principal element alloys (MPEAs) heralds a transformative shift in the design of high‐performance alloys. Their ingrained chemical complexities endow them with exceptional mechanical and functional properties, along with unparalleled microscopic plastic mechanisms, sparking widespread research interest within and beyond the metallurgy community. In this overview, a unique yet prevalent mechanistic process in the renowned FeMnCoCrNi‐based MPEAs is focused on: the dynamic bidirectional phase transformation involving the forward transformation from a face‐centered‐cubic (FCC) matrix into a hexagonal‐close‐packed (HCP) phase and the reverse HCP‐to‐FCC transformation. The light is shed on the fundamental physical mechanisms and atomistic pathways of this intriguing dual‐phase transformation. The paramount material parameter of intrinsic negative stacking fault energy in MPEAs and the crucial external factors c, furnishing thermodynamic, and kinetic impetus to trigger bidirectional transformation‐induced plasticity (B‐TRIP) mechanisms， are thorougly devled into. Furthermore, the profound significance of the distinct B‐TRIP behavior in shaping mechanical properties and creating specialized microstructures c to harness superior material characteristics is underscored. Additionally, critical insights are offered into key challenges and future striving directions for comprehensively advancing the B‐TRIP mechanism and the mechanistic design of next‐generation high‐performing MPEAs. [ABSTRACT FROM AUTHOR]

Thermoelectric materials are crucial components in thermoelectric devices employed for environmentally friendly solid‐state cooling and waste heat recovery, demanding not only high performance but also superior thermal or phase stability. The high‐performance thermoelectric material AgSbTe2 encounters challenges when utilized in thermoelectric modules due to the precipitation of Ag2Te, resulting in both thermally unstable characteristics and diminished performance. In this study, a thermal cycling process is employed to enhance the thermal stability and thermoelectric performance of AgSbTe2. Through thermal cycling, secondary phases of AgSbTe2 are made uniform, and the undesired Ag2Te is substituted with Sb2Te3 using an optimized thermal cycling process. As a result, the thermal stability of AgSbTe2 is enhanced due to its meta‐stable state, with <5% variance in thermoelectric figure of merit (ZT) measurements, and the ZT value is raised from 0.8 to 1.7 at 643 K through the optimized thermal cycling. The findings indicate that thermal cycling is an effective strategy for enhancing the thermal stability and thermoelectric performance of AgSbTe2, presenting a novel approach for achieving uniform secondary phases in materials with phase separation or phase change characteristics. [ABSTRACT FROM AUTHOR]

In the present study, Bi2O3 compositions co–doped with different rare earth oxides were synthesized for IT–SOFC units utilizing the solid–state reaction process under atmospheric conditions. The cubic δ-phase, an excellent ion conductor, was effectively stabilized in certain samples, with XRD patterns including only peaks of that phase. Compositions with more than 35% total dopant concentration exhibited multiple phase structures, particularly monoclinic α and R-phases. The diffraction peak for the (111) plane moved to greater diffraction angles as doping concentration increased, indicating the influence of multiple dopants on the structural features. The lack of both endothermic and exothermic peaks in the patterns proved that there is no phase transition. Arrhenius plots revealed that when overall dopant concentration increased, electrical conductivity dropped primarily because of a lack of cation polarizability. The highest conductivity measured at 750 °C was found to be 0.0228 S.cm–1, with a corresponding activation energy of 0.86 eV. The FE-SEM pictures confirmed that grain size was not uniform over the surface, and it shrank substantially as the total dopant concentration progressively increased, indicating enhanced microstrain in the lattice due to excessive doping. [ABSTRACT FROM AUTHOR]

Nickel-base superalloys contain high amounts of solutes like Cr, Mo, W, Nb, Ti, etc. These solutes promote the formation of different types of carbide and boride phases that may contain multiple elements. Researchers have mostly discussed the roles of primary elements responsible for the formation of a given carbide/boride phase, often ignoring the role of other solutes on its stability. In the present work, thermodynamic stability of carbide and boride phases in seven commercial superalloys, namely, Alloy 625, Alloy 690, Alloy 718, MAR M246, Rene 100, Udimet 710 and Nimonic 80A, has been studied using the CALPHAD based Thermo-Calc software. The aim of the study was to understand the role of different alloying elements on temperature stability and chemical compositions of equilibrium phases in superalloys. As the accuracy of CALPHAD based predictions depends upon the database used, a detailed examination of its inadequacies has also been carried out to ascertain the limitations of the predicted data. From the calculated equilibrium chemical compositions, major and minor constituents promoting the formation of carbides and borides have been identified. The individual effect of a given solute as well as the synergistic effect of two solutes on the relative thermodynamic stability of carbide/boride phases has been identified using property diagrams and isothermal sections of the temperature-composition diagrams. Most of the simulated results have been found to be consistent with the experimental data available in the literature. From a comparison of the experimental literature and the simulated data of the stable carbide and boride phases in the studied alloys, the interplay of different solutes has been deduced to define conditions under which these phases form, within the limitations of the database used. This study has helped in better understanding of general tendencies of solutes to form different carbide and boride phases in nickel-based superalloys. [ABSTRACT FROM AUTHOR]

The effects on phase equilibria of La and Fe additions to the Al–Ce–Ni-based alloy system are explored under high-pressure die casting conditions. The addition of La to Al–Ce–Ni-based alloy system only reacts with Ce synergistically to promote the formation of the Al11(Ce,La)3 intermetallic phase as predicted by CALculation of PHAse Diagrams (CALPHAD) and verified experimentally. High Fe additions react with Ni to form the Al9FeNi intermetallic phase, which is an additional eutectic former. The targeted co-precipitation type eutectic morphology is achieved in the alloys studied. Additional coarse particles of Al11(Ce,La)3, present in the alloys studied and not predicted by CALPHAD, are attributed to possible inclusions of Ce and La oxide, present in the mischmetal feedstock used. Both alloys exhibit exceptional mechanical stability after 10 hours at 400 °C due to the stability of the phases formed during solidification. The alloy with high Fe additions possessed better mechanical properties after heat treatment based on the higher eutectic content and more substantial improvement to the morphology of secondary phases after treatment. [ABSTRACT FROM AUTHOR]

In the present study, the effect of the Nb element on the lattice parameters, phase stability and martensitic transformation behaviors of Ti-Zr-based shape memory alloys was extensively investigated using the first-principles calculation. The lattice parameters of both the β parent phase and α′ martensite phase gradually decreased with Nb content increasing. For the α″ martensite phase, the lattice constant (a) gradually increased with the increase in Nb content, whereas the lattice constants (b and c) continuously decreased due to the addition of Nb. Based on the formation energy and density of state, β→α′ martensitic transformation occurred, as the Nb content was not more than 12.5 at.%. However, the Ti-Zr-Nb shape memory alloys with a Nb content higher than 12.5 at.% possessed the β→α″ martensitic transformation. However, both the largest transformation strain and sensitivity of critical stress to temperature (dσ/dT) can be optimized by controlling 12.5 at.% Nb in the Ti-Zr-Nb shape memory alloy, which was favorable to obtaining the largest elastocaloric effect. [ABSTRACT FROM AUTHOR]

In this study, a novel (α+β) dual-phase Ti–19Nb–0.6O was developed and processed via additive manufacturing, featuring ultra-low Young’s modulus of 42 GPa approximating that of human bone, coupled with high strength (919 MPa), and 15% elongation. By utilizing post-heat treatment to adjust the distribution and content of the precipitated α phase, the elemental distribution of Nb and O between α and β phase was effectively manipulated, meanwhile, the β matrix stability was regulated, enabling the attainment of lower modulus and higher strength. These findings advance the development of biomedical titanium alloys produced using additive manufacturing, characterized by excellent mechanical performance.

Green hydrogen can potentially reduce carbon emissions in several types of automotive, transport and energy industries. However, effective handling of hydrogen during generation, storage, transportation, and distribution poses significant challenges concerning the materials aspect as they are prone to failure. One of the primary reasons for the failure of material is hydrogen embrittlement (HE). This review focuses on developing a new alloy system namely high-entropy alloys (HEAs) to improve and promote microstructure modifications and enhance mechanical properties. Researchers have developed many high-entropy alloys (HEAs) for handling hydrogen to overcome the failure faced by conventional materials. The primary cause of HE in materials is the absence of phase stability and crystal structure changes during hydrogen-induced environments. However, increasing the materials' ductility is more likely to reduce HE failures. Thus, FCC crystal structures are preferred for hydrogen storage materials. Adding multiple elements to increase the entropy level, which supports high-phase stability in all environmental conditions, is an important reason for using HEAs to mitigate HE failures.

The practical application of energetic materials, particularly 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), is frequently impeded by phase transition challenges. In this study, we propose a novel strategy to enhance the stability of CL-20 by employing a thermo-sensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), to modulate its phase transitions. Our approach involves the use of an in-situ polymerized polydopamine (PDA) shell as a platform for surface grafting through atom transfer radical polymerization, yielding a core-shell structured CL-20@PDA-PNIPAM. Through comprehensive characterization, the successful grafting of PNIPAM is confirmed, significantly enhanced the phase stability of CL-20. Notably, our core-shell structure exhibits a 13 °C increase in phase transition temperature compared to raw CL-20, thereby delaying the ε→α phase transition by over 80 min under combined thermal and solvent conditions. The enhanced stability is attributed to the hydrophobic nature of PNIPAM above its low critical solution temperature in water, which effectively shields the CL-20 crystal. These findings provide new insights into enhancing the stability and safety of energetic materials in complex environments, highlighting the potential of our molecular switch mechanism.

The βʹ-Cu4Ti phase is the major strengthening precipitate in Cu–Ti alloys. Previous research indicates that destabilization of the βʹ-Cu4Ti phase leads to dissolution of Ti atom from precipitates into the Cu matrix. In the present work, Sc was chosen to be alloying elements in Cu–Ti alloys, since stabilization of the βʹ-Cu4Ti phase could be enhanced by formation of βʹ-Cu4(Ti,Sc) phase. Experimental characterization combined with first-principles calculations were used to evaluate the effect of Sc addition. It was found that the bonding between Ti and Sc atoms in the same sublattice of βʹ-Cu4Ti phase increases the diffusion barrier of Ti atoms, and thus dissolution of the βʹ-Cu4Ti phase and further nucleation of the β-Cu4Ti phase were hindered.

Unconventional 1T′ phase transition metal dichalcogenides (TMDs) show great potential for hydrogen evolution reaction (HER). However, they are susceptible to transitioning into the stable 2H phase, which reduces their catalytic activity and stability. Herein, we present a scalable approach for designing thermally stable 1T′‐TMDs hollow structures (HSs) by etching Cu1.94S templates from pre‐synthesized Cu1.94S@TMDs heterostructures, including 1T′‐MoS2, MoSe2, WS2, and WSe2 HSs. Furthermore, taking 1T′‐MoS2 HSs as an example, the etched Cu ions can be firmly adsorbed on their surface in the form of single atoms (SAs) through Cu−S bonds, thereby elevating the phase transition temperature from 149 °C to 373 °C. Due to the advantages conferred by the 1T′ phase, hollow structure, and synergistic effect between Cu SAs and 1T′‐MoS2 supports, the fabricated 1T′‐MoS2 HSs demonstrate superior HER performance. Notably, their high‐phase stability enables continuous operation of designed 1T′‐MoS2 HSs for up to 200 hours at an ampere‐level current density without significant activity decay. This work provides a universal method for synthesizing highly stable 1T′‐TMDs electrocatalysts, with a particular focus on the relationship between their phase and catalytic stability. [ABSTRACT FROM AUTHOR]

Method(s) that can reliably predict phase evolution across thermodynamic parameter space, especially in complex systems, are of critical significance in academia as well as in the manufacturing industry. In the present work, the phase stability in an equimolar AlCuFeMn multi-principal-component alloy (MPCA) was predicted using complementary first-principles density functional theory calculations and ab initio molecular dynamics (AIMD) simulations. The temperature evolution of completely disordered, partially ordered, and completely ordered phases was examined based on the Gibbs free energy. Configurational, electronic, vibrational, and lattice mismatch entropies were considered to compute the Gibbs free energy of the competing phases. Additionally, elemental segregation was studied using AIMD. The predicted results at 300 K align well with room-temperature experimental observations using x-ray diffraction and scanning and transmission electron microscopy on a sample prepared using commercially available pure elements. The adopted method could help in predicting plausible phases in other MPCA systems with complex phase stability. [ABSTRACT FROM AUTHOR]

In the study, we synthesized the (BiO 1.5) 0.88 (ErO 1.5) 0.08 (HoO 1.5) 0.04 and (BiO 1.5) 0.88 (ErO 1.5) 0.04 (HoO 1.5) 0.08 ternary compositions using the solid–state reactions in an atmosphere of air. All compositions were then heated to 650, 700, 750, and 800 °C to observe how the calcination temperature impacts phase stability and conductivity. All XRD patterns suggested that the cubic δ–phase, a high–ion conductor, became stable at room temperature. Depending on the temperature, the DTA curves revealed that some compositions had an endothermic peak at around 600 °C, indicating an order–disorder transition wholly related to anion sublattice arrangement without a phase transition. At 700 °C, the highest conductivity was found to be 0.482 S/cm for the (BiO 1.5) 0.88 (ErO 1.5) 0.04 (HoO 1.5) 0.08 composition calcined at 800 °C, and this conductivity is greater than that of a single–doped (BiO 1.5) 0.80 (ErO 1.5) 0.20 system. The FE–SEM images indicated that calcination at 650 °C and 700 °C, which are below the phase transition temperature (729 °C) from α–phase to cubic δ–phase, results in atom aggregation and porosity on the surface. Besides, the calcination temperature was shown to significantly impact grain sizes, with compositions produced with a calcination at 800 °C exhibiting bigger grains than lower ones. [ABSTRACT FROM AUTHOR]

High-Entropy Alloys (HEAs) represent a transformative class of materials characterized by multiple principal elements and high configurational entropy. This review article provides an in-depth examination of their structural particularities, prediction methodologies, and synthesis techniques. HEAs exhibit unique structural stability due to high-entropy effects, severe lattice distortions, and slow diffusion processes. Predictive models, including thermodynamic and kinetic approaches, are essential for understanding phase stability. Various synthesis methods impact HEA properties, and advanced characterization techniques are crucial for their study. The article highlights current applications and future research directions, emphasizing the potential of HEAs in diverse technological fields. [ABSTRACT FROM AUTHOR]

Palladium (Pd) and its alloys, renowned for their good corrosion resistance, catalytic efficiency, and hydrogen affinity, find extensive use in various industrial applications. However, the susceptibility of pure Pd to hydrogen embrittlement necessitates alloying strategies such as Pd-Ag systems. This study investigates the impact of the ordering on the phase stability and elastic properties of Pd-Ag alloys through first-principles calculations. We explore a series of ordered phase structures alongside random solid solutions using Special Quasirandom Structures (SQSs), evaluating their thermodynamic stability and elastic properties. Our findings indicate the possible existence of stable ordered L12 Pd3Ag and PdAg3 and L11 PdAg phases, which are thought to exist only in Cu-Pt alloys. An analysis of the elastic constants and anisotropy indices underscores some pronounced directional dependencies in the mechanical responses between the random solid-solution and ordered phases. This suggests that the ordered phases not only are thermodynamically and mechanically more stable than solid-solution phases, but also display a decrease in anisotropy indices. The results provide a deeper understanding of the atomic behavior of Pd-Ag alloys, and shed light on the design of multiphase Pd-Ag alloys to improve their mechanical properties. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite CsPbI3 is emerging as a thermally more stable alternative to organic-inorganic hybrid perovskites. However, CsPbI3 perovskite suffers from poor phase stability at ambient temperature, and its bandgap is a bit too large as light-harvesting materials in both single-junction and perovskite-on-silicon tandem solar cells. In this study, we propose an electrically neutral co-doping strategy that equimolar Bi3+ (occupying the Pb site) and Cl– (occupying the interstitial site) are incorporated into CsPbI3. Unlike the individual Bi3+ or Cl– doping, the neutral co-doping can avoid stimulating the formation of the detrimental native defects. Our first-principles calculations suggest that the co-doped systems are stable at ambient temperature and possess narrower bandgaps compared with the undoped CsPbI3. Moreover, the electron and hole states are spatially separated in these multiple-ion compounds. [ABSTRACT FROM AUTHOR]

Stabilized Li6.25La3Al0.25 Zr2O12 (cubic LLZO or c-LLZO) is a Li+-conducting ceramic with ionic conductivities approaching 1 mS-cm. Processing c-LLZO so that it is suitable for use as a solid state electrolyte in all solid state batteries, however, is challenging due to the formation of secondary phases at elevated temperatures. The work described in this manuscript examines the formation of one such secondary phase La2Zr2O7 (LZO) formed during sintering c-LLZO at 1000 °C. Specifically, spatially resolved Raman spectroscopy and X-ray Diffraction (XRD) measurements have identified gradients in Li distributions in the Li ion (Li+)-conducting ceramic Li6.25La3Al0.25 Zr2O12 (cubic LLZO or c-LLZO) created by thermal processing. Sintering c-LLZO under conditions relevant to solid state Li+ electrolyte fabrication conditions lead to Li+ loss and the formation of new phases. Specifically, sintering for 1 h at 1000 °C leads to Li+ depletion and the formation of the pyrochlore lanthanum zirconate (La2Zr2O7 or LZO), a material known to be both electronically and ionically insulating. Circular c-LLZO samples are covered on the top and bottom surfaces, exposing only the 1.6 mm-thick sample perimeter to the furnace's ambient air. Sintered samples show a radially symmetric LZO gradient, with more LZO at the center of the pellet and considerably less LZO at the edges. This profile implies that Li+ diffusion through the material is faster than Li+ loss through volatilization, and that Li+ migration from the center of the sample to the edges is not completely reversible. These conditions lead to a net depletion of Li+ at the sample center. Findings presented in this work suggest new strategies for LLZO processing that will minimize Li+ loss during sintering, leading to a more homogeneous material with more reproducible electrochemical behavior. [ABSTRACT FROM AUTHOR]

A series of cathode materials of Pr 2-x Sr x NiO 4 (x = 0, 0.3, 0.5, 0.7, 1, 1.5) are synthesized by the EDTA-citric acid route. The results show that the Pr 1.7 Sr 0.3 NiO 4 , Pr 1.5 Sr 0.5 NiO 4 , Pr 1.3 Sr 0.7 NiO 4 and PrSrNiO 4 exhibit excellent structural stability and carbon dioxide resistance, and also exhibit good chemical compatibility and thermal matching with the SDC electrolyte. It is also found that the Sr doping is beneficial in improving the high temperature conductivity of Pr 2-x Sr x NiO 4. At 800 °C, the electrical conductivity of Pr 1.5 Sr 0.5 NiO 4 and Pr 1.3 Sr 0.7 NiO 4 reaches 185 S cm−1 and 317 S cm−1, respectively. In addition, the area-specific resistance (ASR) value increases significantly with Sr doping, which reduces the catalytic activity of the material. Acceptable ASR values are obtained for Pr 1.5 Sr 0.5 NiO 4 and Pr 1.3 Sr 0.7 NiO 4 , with ASR values of 0.079 Ω cm2 and 0.082 Ω cm2 at 800 °C, respectively. Additionally, the most interesting result is the ASR value obtained after high-temperature thermal decomposition of Pr 2 NiO 4 , where Pr 2 NiO 4 * (decomposed) has the lowest ASR value of only 0.027 Ω cm2 at 800 °C, showing the best catalytic activity. The maximum power densities of Pr 2-x Sr x NiO 4 (x = 0.5 and 0.7) and Pr 2 NiO 4 * are found to be 515, 430, and 548 mW cm−2 at 800 °C, respectively. These results show that when the Sr doping amount is less than 1.5, the stability of the Pr 2-x Sr x NiO 4 cathode material can be effectively improved, but its catalytic performance is partially sacrificed. [ABSTRACT FROM AUTHOR]

Notwithstanding the impressive phase stability and low thermal conductivity exhibited by lanthanum zirconate (LZ), its low coefficient of thermal expansion is deemed a paramount limitation. In the present study, (La 1-x Y x) 2 Zr 2 O 7 with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, as new TBCs, were synthesized by reverse co-precipitation and calcination method. The XRD and Raman analyses elucidated that the substitution of Y3+ ions occurred exclusively at the La3+ positions. In addition, in accordance with FESEM and DTA findings, the incorporation of Y 2 O 3 has induced a reduction in particle size and an enhancement in crystallization resistance. The evaluation of the coefficient of thermal expansion (CTE) demonstrated a notable improvement following the introduction of Y 2 O 3. Specifically, the CTE of LZ increased from 9.34 × 10−6 °C-1 to 10.5 × 10−6 °C-1 in the case of (La 0.5 Y 0.5) 2 Zr 2 O 7 at 1100oC. Investigations of phase stability following a 50 h heat treatment at 1300oC indicated that Y 2 O 3 had no impact on phase stability. All compounds, similar to LZ, exhibited excellent phase stability. Furthermore, the addition of Y 2 O 3 significantly amplified the grain boundary diffusion mechanism during heat treatment, leading to an accelerated grain growth rate. The grain growth rate increased from 1.7 nm/h at LZ to 2.2 nm/h in the case of (La 0.6 Y 0.4) 2 Zr 2 O 7. [ABSTRACT FROM AUTHOR]

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The practical application of energetic materials, particularly 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12- hexaazaisowurtzitane (CL-20), is frequently impeded by phase transition challenges. In this study, we propose a novel strategy to enhance the stability of CL-20 by employing a thermo-sensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), to modulate its phase transitions. Our approach involves the use of an in-situ polymerized polydopamine (PDA) shell as a platform for surface grafting through atom transfer radical polymerization, yielding a core-shell structured CL-20@PDA-PNIPAM. Through comprehensive characterization, the successful grafting of PNIPAM is confirmed, significantly enhanced the phase stability of CL-20. Notably, our core-shell structure exhibits a 13ºC increase in phase transition temperature compared to raw CL-20, thereby delaying the ε→ α phase transition by over 80 min under combined thermal and solvent conditions. The enhanced stability is attributed to the hydrophobic nature of PNIPAM above its low critical solution temperature in water, which effectively shields the CL-20 crystal. These findings provide new insights into enhancing the stability and safety of energetic materials in complex environments, highlighting the potential of our molecular switch mechanism [ABSTRACT FROM AUTHOR]

Pure FAPbI3‐based, with FA being formamidinium, perovskite solar cells (PSCs) have garnered worldwide recognition for their exceptional efficiency. However, the phase stability of FAPbI3 is still a big obstacle in this area, because the ordinary strategy using MA+, Br−, Cs+ to stabilize α‐FAPbI3 phase can cause the bandgap change and ion migration. Herein, a new strategy is introduced to improve the α‐FAPbI3 phase stability by using a self‐assembled bridging layer at the buried interface of FAPbI3 perovskite in the n–i–p solar cell structure. A series of multidentate bisphosphonic acid molecules are screened and demonstrate that etidronic acid (EA) with the smallest steric hindrance behaves the best. The four P‐OH groups can first form multidentate anchors on SnO2 while the remaining unanchored ─OH and P═O groups can form strong interaction between I− and Pb2+. Thus, a strong and stable bridging layer is formed, which greatly increases the energy barrier of phase transition of FAPbI3. As a result, the pure FAPbI3‐based (MA+, Br+, Cs+‐free system) n–i–p device reached an impressive power conversion efficiency of 24.2% with good stability. Furthermore, the strong interaction between EA and Pb2+ can greatly reduce lead leakage in harsh conditions. [ABSTRACT FROM AUTHOR]

The high-temperature oxidation behaviour and phase stability of equi-atomic high entropy AlCrCoFeNi alloy (HEA) were studied using in situ high-temperature X-ray diffraction (HTXRD) combined with ThermoCalc thermodynamic calculation. HTXRD analyses reveal the formation of B2, BCC, Sigma and FCC, phases at different temperatures, with significant phase transitions observed at intermediate temperatures from 600 °C–100 °C. ThermoCalc predicted phase diagram closely matched with in situ HTXRD findings highlighting minor differences in phase transformation temperature. ThermoCalc predictions of oxides provide insights into the formation of stable oxide phases, predominantly spinel-type oxides, at high p(O2), while a lower volume of halite was predicted, and minor increase observed with increasing temperature. The oxidation behaviour was strongly dependent on the environment, with the vacuum condition favouring the formation of a thin, Al2O3 protective layer, while in atmospheric conditions a thick, double-layered oxide scale of Al2O3 and Cr2O3 formed. The formation of oxide scale was determined by selective oxidation of Al and Cr, as further confirmed by EDX analysis. The formation of thick oxide in air environment resulted in a thick layer of Al-depleted FFC phase. This comprehensive study explains the high-temperature phase stability and time–temperature-dependent oxidation mechanisms of AlCrCoFeNi HEA. The interplay between surface phase transformation beneath oxide scale and oxides is also detailed herein, contributing to further development and optimisation of HEA for high temperature applications. [ABSTRACT FROM AUTHOR]

Single stabilizer-doped ZrO 2 has drawbacks such as inferior mechanical properties and thermal stability, making it difficult to obtain ZrO 2 ceramics with good density and high crystallinity. Thus, it is expected that ZrO 2 is doped and modified by two or more stabilizers. In this paper, the Sc 2 O 3 –Y 2 O 3 –ZrO 2 nanocomposite ceramic powders were prepared using ZrOCl 2 ⋅8H 2 O, ScCl 3 ⋅6H 2 O, and YCl 3 ⋅6H 2 O as raw materials and polyvinylpyrrolidone as dispersant. They calcined at diverse temperaturesby the pressureless sintering-assisted co-precipitation method after being pressed into disc shape. Sc 2 O 3 and Y 2 O 3 were added as ZrO 2 stabilizers to ameliorate the lack of insufficient mechanical properties and high-temperature stability of ZrO 2 ceramics caused by single doping. To study the stability of the phases at high temperatures, the specimens were characterized by TG-DTG, XRD, Raman, SEM, FT-IR, etc. The effects of different pH valuesand different calcination temperatures on the Sc 2 O 3 –Y 2 O 3 –ZrO 2 nanocomposite ceramics were investigated. It was demonstrated that ternary doping has very excellent phase stability. After calcination no monoclinic phase appeared, and the precursor samples were transformed from amorphous to a large amount of tetragonal phases and a few cubic phases. The samples at pH = 10 and calcination temperature of 1000 °C showed the best stabilization, the most uniform grain development, the best crystallinity, the most regular morphology, the highest tetragonal phase content of 89.2 %, the stabilization rate of 94.58 %, and the highest relative density of 98.75 %. The results show that this nanocrystalline powder can be used to prepare high-density nanoceramics. Furthermore, the activation energy for grain growth of Sc 2 O 3 –Y 2 O 3 –ZrO 2 nanocomposite ceramics was calculated as 13.87 kJ/mol. This paper provides a theoretical and experimental research basis for the controlled synthesis of Sc 2 O 3 –Y 2 O 3 –ZrO 2 nanocomposite ceramics using a pressureless sintering-assisted co-precipitation method. [ABSTRACT FROM AUTHOR]

Inorganic perovskites, with Cs+ substituting volatile organic components, show great promise in photovoltaic applications due to their outstanding optoelectronic properties and thermal stability. However, the black‐to‐yellow phase transition of CsPbI3 remains a challenge for realizing high‐performance inorganic perovskite solar cells (IPSCs). Herein, an effective approach is reported via incorporating the self‐assembled molecule Me‐4PACz to synergistically stabilize the [PbI6]4− octahedra and form a hydrophobic layer at interface and grain boundaries. An in situ dehydration condensation reaction of Me‐4PACz is observed during film annealing, which favors the reduction of undesired aggregation of Me‐4PACz in humid air, thus leading to enhanced anchoring interaction and more effective hydrophobic protection of CsPbI3. Therefore, the air‐processed CsPbI3 perovskite films show dramatically improved phase purity and humid stability. This strategy also improves the energy level alignment between perovskite and charge transport layers. As a result, a champion efficiency of 20.21% is realized, representing one of the highest reported values for air‐processed inverted IPSCs. Furthermore, it is demonstrated that by combining Me‐4PACz with the previously reported ethacridine lactate (EAL) additive, the device performance can be further boosted to 21.38%, which is a record efficiency for the inverted IPSCs reported to date. [ABSTRACT FROM AUTHOR]

Context: The present study reports the properties of pressure-induced phase transition, electronic and optical of phosphides XSiP2 under pressure in chalcopyrite, sodium chloride (rock salt), and Wurtzite phases. The study shows the chalcopyrite phase as the most stable phase among the other studied phases. The obtained structural parameters in the chalcopyrite and rock-salt phases reasonably agree with the literature. The computed band structures revealed a semiconductor behavior in chalcopyrite structure and metallic behavior for rock- salt and wurtzite structures. In the energy range of 0 to 30 eV, optical parameters such as the real and imaginary parts of the dielectric constant, refractive index, and reflectivity are calculated and compared with existing data. Our optical properties findings are predictive for the rock-salt and wurtzite phases. Since no results are available in the literature, these results may serve as references for other theoretical and experimental studies. Method: The calculations are performed by employing the "full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT)." [ABSTRACT FROM AUTHOR]

This study investigates the structural stability, electronic structure, and elastic and thermodynamic properties of Au-Al intermetallic compounds (IMCs) using first-principles calculations based on density functional theory, and further discusses their hardness and toughness values. AuAl2, AuAl, Au2Al, Au8Al3 and Au4Al are all phases of the Au-Al alloy. The calculated cohesive energy and enthalpy of formation show that AuAl2 has the best phase stability. Analysis of the electronic structure of each phase shows that the covalent bond characteristics weaken with the increase in Au content, among which Au4Al has the weakest covalent bond characteristics and the lowest hardness value. In addition, the Debye temperature and thermal conductivity of each phase are analyzed. [ABSTRACT FROM AUTHOR]

The recent surge in interest in high-entropy oxides (HEOs) as a novel class of ceramic materials can be attributed to the remarkable performance enhancements caused by both the complexity of their chemical composition and the simplicity of their structure. The extensive range of components presents challenges to the implementation of HEOs, rendering it difficult to predict the phase structure prior to the final synthesis. Herein, semi-empirical methods based on various parameters, including ΔX, VEC, ΔSmix, ΔHmix and δ, were utilized to determine the phase stability of rock salt, spinel, perovskite and fluorite structures. The combination of δ with ΔX, VEC, ΔSmix, and ΔHmix, in graphical form, is an effective indicator for determining the phase stability of rock salt, perovskite and fluorite structures. The spinel structure is stabilized outside the range of the other three structures. The phase formation rules were further verified with two newly designed and prepared HEOs via X-ray diffraction and high-resolution transmission electron microscopy. The HEOs show potential for functional applications, e.g., methyl orange degradation.

Abstract The emergence of multi‐principal element alloys (MPEAs) heralds a transformative shift in the design of high‐performance alloys. Their ingrained chemical complexities endow them with exceptional mechanical and functional properties, along with unparalleled microscopic plastic mechanisms, sparking widespread research interest within and beyond the metallurgy community. In this overview, a unique yet prevalent mechanistic process in the renowned FeMnCoCrNi‐based MPEAs is focused on: the dynamic bidirectional phase transformation involving the forward transformation from a face‐centered‐cubic (FCC) matrix into a hexagonal‐close‐packed (HCP) phase and the reverse HCP‐to‐FCC transformation. The light is shed on the fundamental physical mechanisms and atomistic pathways of this intriguing dual‐phase transformation. The paramount material parameter of intrinsic negative stacking fault energy in MPEAs and the crucial external factors c, furnishing thermodynamic, and kinetic impetus to trigger bidirectional transformation‐induced plasticity (B‐TRIP) mechanisms， are thorougly devled into. Furthermore, the profound significance of the distinct B‐TRIP behavior in shaping mechanical properties and creating specialized microstructures c to harness superior material characteristics is underscored. Additionally, critical insights are offered into key challenges and future striving directions for comprehensively advancing the B‐TRIP mechanism and the mechanistic design of next‐generation high‐performing MPEAs.

Transition metal-ruthenium alloys are promising candidates for ultra-high-temperature structural applications. However, the mechanical and electronic characteristics of these alloys are not well understood in the literature. This study uses first-principles density functional theory calculations to explore the structural, electronic, mechanical, and phonon properties of X3Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) binary alloys in the tP16 crystallographic phase. We find that Mn3Ru, Sc3Ru, Ti3Ru, V3Ru, and Zn3Ru have negative heats of formation and hence are thermodynamically stable. Mechanical analysis (Cij) indicates that all tP16-X3Ru alloys are mechanically stable except, Fe3Ru and Cr3Ru. Moreover, these compounds exhibit ductility and possess high melting temperatures. Furthermore, phonon dispersion curves indicate that Cr3Ru, Co3Ru, Ni3Ru, and Cu3Ru are dynamically stable, while the electronic density of states reveals all the X3Ru alloys are metallic, with a significant overlap between the valence and conduction bands at the Fermi energy. These findings offer insights into the novel properties of the tP16 X3Ru intermetallic alloys for the exploration of high-temperature structural applications.

As a promising material for the advanced thermal barrier coatings (TBCs), scandium oxide (Sc 2 O 3) and yttrium oxide (Y 2 O 3) co-stabilized zirconia (ScYSZ) has been given increasing attention during the past decade. In this study, three types of TBCs including YSZ, ScYSZ and ScYSZ-YSZ double ceramic layer (DCL) coatings were deposited by a wide-velocity range high-energy plasma spraying technology. The thermal physical property, phase stability and thermal cycling performance of TBCs were comparatively studied. The results suggested that the thermal conductivity from 200 °C to 1000 °C of ScYSZ coating was reduced by approximately 30 % compared to the YSZ coating. After exposure at 1400 °C for 1000 h, the ScYSZ coating still kept the initial tetragonal phase structure, while the tetragonal phase was completely disappeared in the YSZ coating after 300 h at 1400 °C. Notably, the ScYSZ-YSZ DCL coating demonstrated the highest thermal cycling life within the temperature range of 1320∼1370 °C, exhibiting a remarkable 43 % increase over the single ScYSZ coating and doubling that of the single YSZ coating. The outcomes of this study hold significant promise for practical applications in the realm of high-performance TBCs. [ABSTRACT FROM AUTHOR]

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Cesium‐based all‐inorganic wide‐bandgap perovskite solar cells (AIWPSCs) have been demonstrated with exceptional optoelectronic properties such as intrinsic optical wide‐bandgap and high thermal stability, which make them suitable candidates for the front sub‐cells of tandem solar cells (TSCs). Passivation of perovskite surface and interface is a matter of common interest in this community since all‐inorganic perovskites always suffer from non‐ideal crystallization such as phase impurity, high defect density, and non‐uniform morphology. Despite these shortcomings, numerous efforts have been devoted in recent years to pursuing high‐performance AIWPSCs, which exhibit an abruptly increased power conversion efficiency (PCE) from 2.9% to over 21.0%. In view of not having a thorough summary about the advancements on AIWPSCs, herein, a comprehensive review is given to highlight the recent device performance progress of AIWPSC, particularly focusing on the strategies to passivate the defects of all‐inorganic perovskite, namely, additive engineering, solvent engineering, interface modification, and the exploration of new charge transport materials (CTMs) for improving the phase stability and PCE of AIWPSCs. Finally, a conclusive outlook on AIWPSCs will be given to provide our perspectives aiming to inspire the further development of AIWPSCs. [ABSTRACT FROM AUTHOR]

Transition metal-ruthenium alloys are promising candidates for ultra-high-temperature structural applications. However, the mechanical and electronic characteristics of these alloys are not well understood in the literature. This study uses first-principles density functional theory calculations to explore the structural, electronic, mechanical, and phonon properties of X3Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) binary alloys in the tP16 crystallographic phase. We find that Mn3Ru, Sc3Ru, Ti3Ru, V3Ru, and Zn3Ru have negative heats of formation and hence are thermodynamically stable. Mechanical analysis (Cij) indicates that all tP16-X3Ru alloys are mechanically stable except, Fe3Ru and Cr3Ru. Moreover, these compounds exhibit ductility and possess high melting temperatures. Furthermore, phonon dispersion curves indicate that Cr3Ru, Co3Ru, Ni3Ru, and Cu3Ru are dynamically stable, while the electronic density of states reveals all the X3Ru alloys are metallic, with a significant overlap between the valence and conduction bands at the Fermi energy. These findings offer insights into the novel properties of the tP16 X3Ru intermetallic alloys for the exploration of high-temperature structural applications. [ABSTRACT FROM AUTHOR]

A non-equiatomic Fe34.9Ni30.2Mn18.6Cr9.3Al7 high-entropy alloy (HEA) was synthesized by mechanical alloying using different milling times. To study the effect of milling time on the structure stability, X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive X-ray spectroscopy were conducted. For comparison, an Al-free alloy (Fe37.5Ni32.5Mn20Cr10) was produced at 25 h milling. XRD indicated a single FCC phase alloy after 5 h milling time and a dual FCC and BCC phase at 25 h milling time. Clearly, it is found that Al addition is not necessarily the main factor leading to BCC phase formation as reported for similar HEAs produced by casting route. Increasing the milling time, the lattice strain increased reaching an average maximum value of 0.8% with an increase in d-spacing while the crystallite size was reduced to about 5.7 nm. A dual-phase structure formation was related to a decrease in the accumulated strain (ca.32%) confirming a strain-induced transformation. [ABSTRACT FROM AUTHOR]

Since the certified power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached 26.1%, exactly equal to that of crystalline silicon solar cells, a strong demand for ensuring the long‐term stability of PSCs has arisen for commercialization. The intrinsic stability of the perovskite layer must be guaranteed as a top priority to ensure the whole device's stability. Recently, the state‐of‐the‐art PSCs, performing a high PCE, employ α‐FAPbI3 (FA = formamidinium) for the perovskite layer in spite of its metastable tendency to spontaneously transform into its photoinactive polymorph at PSC operating temperature. In this review paper, the intrinsic structural stability of α‐FAPbI3 soft lattice is understood from the thermodynamic point of view, with key parameters to restrain the undesirable phase transition. Besides, reported experimental results are closely examined to find fundamental origins, derive the enhanced phase stability in each experiment, and understand their role in maintaining the lattice structure from the collective perspective. [ABSTRACT FROM AUTHOR]