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We present large-scale atomistic simulations that reveal triple junction (TJ) segregation in Pt-Au nanocrystalline alloys in agreement with experimental observations. While existing studies suggest grain boundary solute segregation as a route to thermally stabilize nanocrystalline materials with respect to grain coarsening, here we quantitatively show that it is specifically the segregation to TJs that dominates the observed stability of these alloys. Our results reveal that doping the TJs renders them immobile, thereby locking the grain boundary network and hindering its evolution. In dilute alloys, it is shown that grain boundary and TJ segregation are not as effective in mitigating grain coarsening, as the solute content is not sufficient to dope and pin all grain boundaries and TJs. Our work highlights the need to account for TJ segregation effects in order to understand and predict the evolution of nanocrystalline alloys under extreme environments.

Abstract: Addressing sustainable energy storage remains crucial for transitioning to renewable sources. While Li‐ion batteries have made significant contributions, enhancing their capacity through alternative materials remains a key challenge. Micro‐sized silicon is a promising anode material due to its tenfold higher theoretical capacity compared to conventional graphite. However, its substantial volumetric expansion during cycling impedes practical application due to mechanical failure and rapid capacity fading. A novel approach is proposed to mitigate this issue by incorporating trace amounts of aluminum into the micro‐sized silicon electrode using ball milling. Density functional theory (DFT) is employed to establish a theoretical framework elucidating how grain boundary sliding, a key mechanism involved in preventing mechanical failure is facilitated by the presence of trace aluminum at grain boundaries. This, in turn, reduces stress accumulation within the material, reducing the likelihood of failure. To validate the theoretical predictions, capacity retention experiments are conducted on undoped and Al‐doped micro‐sized silicon samples. The results demonstrate significantly reduced capacity fading in the doped sample, corroborating the theoretical framework and showcasing the potential of aluminum doping for improved Li‐ion battery performance.

Hydrogen segregation behaviors at BCC-Fe Σ3 (111) grain boundary (GB) as well as the effects of alloying solutes were studied by the first-principles method. The segregation energy of alloying solutes at different periods presents a concave-down parabolic-like relationship with the atomic number, and the 4 d transition alloying solutes show a higher averaged segregation tendency. At the favorable trapping site, hydrogen segregation energy decreased by increasing the number of hydrogen atoms up to 0.85/Å2 in the plane vertical to the GB. Mo, Tc, Ru, Ta, W, Re, Os, and Ir strengthen GB and inhibit hydrogen segregation. Significantly, the interaction between alloying solutes and hydrogen segregation was elucidated by emphasizing the separation of the chemical and the mechanical contributions, and appropriate descriptors on hydrogen segregation energy influenced by alloying solutes were screened. This work offers theoretical backing to comprehend hydrogen segregation behaviors and the effects of alloying solutes to design advanced high-strength steels resistant to hydrogen embrittlement. • Hydrogen segregation behaviors at pure BCC Σ3 (111) grain boundary were studied. • Alloy solute segregation behaviors at pure BCC Σ3 (111) grain boundary were studied. • Interaction between alloying solutes and hydrogen at grain boundary was elucidated. • Descriptors on hydrogen segregation energy at grain boundary were screened. • Relationship between hydrogen segregation at grain boundary and HE was discussed. [ABSTRACT FROM AUTHOR]

NASICON-structured Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP) solid electrolyte has low grain boundary conductivity, which impedes its practical application. Herein, W was adopted to partially replace the Al element in LATP to improve its grain boundary conductivity. The W doping reduces the crystal lattice of the electrolyte, which is detrimental to the grain conductivity. But the doping of W can make the grains closely connect and reduce the voids between the grains, which can greatly enhance the grain boundary conductivity. The LATP sample with the W doping content of 0.03 (LATWP003) exhibits the highest total ionic conductivity of 1.186 mS/cm at 30 ℃, which results from the optimum grain boundary conductivity of 2.315 mS/cm. Moreover, the LATWP003 electrolyte displays a negligible electronic conductivity of 2.01×10−9 S/cm. The LiFePO 4 /LATWP003/Li battery with PVDF-HFP polymer protective layer can be charged and discharged. Therefore, the W doped LATP sample is a promising electrolyte for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A nonlocal phase-field crystal (NPFC) model is presented as a nonlocal counterpart of the local phase-field crystal (LPFC) model and a special case of the structural PFC (XPFC) derived from classical field theory for crystal growth and phase transition. The NPFC incorporates a finite range of spatial nonlocal interactions that can account for both repulsive and attractive effects. The specific form is data-driven and determined by a fitting to the materials structure factor, which can be much more accurate than the LPFC and previously proposed fractional variant. In particular, it is able to match the experimental data of the structure factor up to the second peak, an achievement not possible with other PFC variants studied in the literature. Both LPFC and fractional PFC (FPFC) are also shown to be distinct scaling limits of the NPFC, which reflects the generality. The advantage of NPFC in retaining material properties suggests that it may be more suitable for characterizing liquid–solid transition systems. Moreover, we study numerical discretizations using Fourier spectral methods, which are shown to be convergent and asymptotically compatible, making them robust numerical discretizations across different parameter ranges. Numerical experiments are given in the two-dimensional case to demonstrate the effectiveness of the NPFC in simulating crystal structures and grain boundaries. [ABSTRACT FROM AUTHOR]

In boundary lubrication, the detachment of lubricant molecules from a solid surface is likely to occur due to the presence of high compressive normal stress combined with shear stress exerted on the solid–liquid interface. This phenomenon often results in a delamination behavior at the interface. We aim to investigate the nanoscale roughness effect on the oil film delamination from sliding iron surfaces with grain boundaries by coarse-grained molecular dynamics simulations. As a result, the oil film delamination was effectively suppressed in higher roughness. Two distinct mechanisms of delamination were found depending on surface roughness when the critical normal stress is exceeded. High roughness enhanced the ability to prevent complete slip but had negligible influence on partial slip. [ABSTRACT FROM AUTHOR]

Aqueous Zn metal batteries (ZMBs) are largely hampered by the poor stability of zinc (Zn) anode in aqueous electrolyte due to uncontrollable deposition behavior and parasitic reactions. Hence, a stable Glu@Zn anode via acid etching is developed that simultaneously exposes (002) plane and modifies exposed grain boundaries. The surface‐preferred (002) plane is achieved by minimizing its surface energy. And the exposed grain boundaries are also modified by decomposition products of acid etching, which can greatly reduce the adverse effects caused by highly active grain boundaries. These features favor Glu@Zn anode by accrediting a long‐term cycle lifespan exceeding 4400 h with a high average coulombic efficiency (CE) of 98.9%. Surprisingly, Glu@Zn anode can run for more than 250 h with 50% Zn utilization. The assembled Glu@Zn//NH4V4O10 full batteries deliver a specific capacity of 291.6 mAh g−1 after 400 cycles even at a low current density of 0.5 A g−1. It can also obtain a stable cycling performance up to 2000 cycles. To further verify its stability, a pouch cell is constructed that can preserve stable 400 cycles with 5 mAh. This study sheds light on surface energy regulation exposing preferred crystal plane to develop highly stable and reversible cycling aqueous ZMBs. [ABSTRACT FROM AUTHOR]

Anisotropic bulk magnets of ThMn12-type SmFe10V2 with a high coercivity (Hc) were successfully fabricated. Powders with varying particle sizes were prepared using the ball milling process, where the particle size was controlled with milling time. A decrease in Hc occurred in the heat-treated bulk pressed from large-sized powders, while heavy oxidation excessively occurred in small powders, leading to the decomposition of the SmFe10V2 (1–12) phase. The highest Hc of 8.9 kOe was achieved with powders ball-milled for 5 h due to the formation of the grain boundary phase. To improve the maximum energy product ((BH)max), which is only 2.15 MGOe in the isotropic bulk, anisotropic bulks were prepared using the same powders. The easy alignment direction, confirmed by XRD and EBSD measurements, was <002>. Significant enhancements were observed, with saturation magnetization (Ms) increasing from 59 to 79 emu/g and a remanence ratio (Mr/Ms) of 83.7%. (BH)max reaching 7.85 MGOe. For further improvement of magnetic properties, controlling oxidation is essential to form a uniform grain boundary phase and achieve perfect alignment with small grain size. [ABSTRACT FROM AUTHOR]

All-solid-state lithium batteries have great potential applying to the fields of transportation and portable devices because of their high safety and energy density as the power source. As a critical component of device, solid-state electrolyte has been paid much attention. Given the excellent physical and chemical stability, Li 1+ x Al x Ti 2- x (PO 4) 3 (LATP)-based electrolyte has been considered as one of the most promising electrolytes for the next generation batteries. However, a further promotion of its ionic conductivity becomes extremely difficult, originating mainly from the poor connection of grains and a low relative density of LATP. Here, the nanosized and homogenous LATP (x = 0.3) powders were synthesized through reducing the agglomeration of precursor powders and preparing at low temperatures. It is revealed that uniformly superfine LATP powders are able to improve the microstructure of grain boundaries during the pellet sintering process, thereby reducing the grain boundary resistance. Furthermore, as-synthesized nanosized powders mixed with Bi 2 O 3 additive present a better enhancement on the connection of grains and the relative density in LATP. On the basis of this understanding, we prepared LATP electrolytes with 0.5 wt% Bi 2 O 3 exhibiting a high ionic conductivity of 8.56 × 10−4 S/cm, a high relative density of 94.4 % and a low activation energy of 0.27 eV, which is demonstrated as a prospective electrolyte in all-solid-state lithium battery LiFePO 4 /PEO/LATP/PEO/Li. [ABSTRACT FROM AUTHOR]

Aqueous Zn‐ion batteries are an attractive electrochemical energy storage solution for their budget and safe properties. However, dendrites and uncontrolled side reactions in anodes detract the cycle life and energy density of the batteries. Grain boundaries in metals are generally considered as the source of the above problems but we present a diverse result. This study introduces an ultra‐high proportion of grain boundaries on zinc electrodes through femtosecond laser bombardment to enhance stability of zinc metal/electrolyte interface. The ultra‐high proportion of grain boundaries promotes the homogenization of zinc growth potential, to achieve uniform nucleation and growth, thereby suppressing dendrite formation. Additionally, the abundant active sites mitigate the side reactions during the electrochemical process. Consequently, the 15 μm Fs−Zn||MnO2 pouch cell achieves an energy density of 249.4 Wh kg−1 and operates for over 60 cycles at a depth‐of‐discharge of 23 %. The recognition of the favorable influence exerted by UP‐GBs paves a new way for other metal batteries. [ABSTRACT FROM AUTHOR]

The remarkable stability, suitable thermomechanical characteristics, and acceptable electrical properties of donor-doped strontium titanates make them attractive materials for fuel electrodes, interconnects, and supports of solid oxide fuel and electrolysis cells (SOFC/SOEC). The present study addresses the impact of processing and thermochemical treatment conditions on the electrical conductivity of SrTiO3-derived ceramics with moderate acceptor-type substitution in a strontium sublattice. A-site-deficient Sr0.85La0.10TiO3−δ and cation-stoichiometric Sr0.85Pr0.15TiO3+δ ceramics with varying microstructures and levels of reduction have been prepared and characterized by XRD, SEM, TGA, and electrical conductivity measurements under reducing conditions. The analysis of the collected data suggested that the reduction process of dense donor-doped SrTiO3 ceramics is limited by sluggish oxygen diffusion in the crystal lattice even at temperatures as high as 1300 °C. A higher degree of reduction and higher electrical conductivity can be obtained for porous structures under similar thermochemical treatment conditions. Metallic-like conductivity in dense reduced Sr0.85La0.10TiO3−δ corresponds to the state quenched from the processing temperature and is proportional to the concentration of Ti3+ in the lattice. Due to poor oxygen diffusivity in the bulk, dense Sr0.85La0.10TiO3−δ ceramics remain redox inactive and maintain a high level of conductivity under reducing conditions at temperatures below 1000 °C. While the behavior and properties of dense reduced Sr0.85Pr0.15TiO3+δ ceramics with a large grain size (10–40 µm) were found to be similar, decreasing grain size down to 1–3 µm results in an increasing role of resistive grain boundaries which, regardless of the degree of reduction, determine the semiconducting behavior and lower total electrical conductivity of fine-grained Sr0.85Pr0.15TiO3+δ ceramics. Oxidized porous Sr0.85Pr0.15TiO3+δ ceramics exhibit faster kinetics of reduction compared to the Sr0.85La0.10TiO3−δ counterpart at temperatures below 1000 °C, whereas equilibration kinetics of porous Sr0.85La0.10TiO3−δ structures can be facilitated by reductive pre-treatments at elevated temperatures. [ABSTRACT FROM AUTHOR]

The microscopic mechanical properties including the bending strength and Young's modulus for Si 3 N 4 ceramics doped with Y 2 O 3 and Al 2 O 3 which was immersed in 5 wt% sulfuric acid solution using microcantilever beam specimens was investigated in comparison with the macroscopic results obtained in conventional three-point bending tests. Both the properties sharply dropped in very short periods of the corrosion in the microcantilever tests, resulting from the dissolutions of yttrium and aluminum ions of grain boundary glass networks, followed by the hydration. After the drops at the beginning of the corrosion, they showed little degradation afterwards. The degradation behaviors of the mechanical properties are basically the same as those in conventional macroscopic approaches; however, they changes appear in very short periods of the corrosion in the microcantilever bending tests. This study also verified that a small difference of a ratio of sintering additives results in different grain boundary strengths of Si 3 N 4 ceramics. [ABSTRACT FROM AUTHOR]

Texturation and anisotropic performance of Ca 3 Co 4 O 9 -based ceramics fabricated by spark plasma sintering were reported, showing promising thermoelectric properties. With template seeds simultaneous additives, the high degree of texturing was obtained. Electrical resistivity decreased from 16.9 to 6.1 mΩ cm and Seebeck coefficient increased from 75.8 to 187.6 μV/K for the sample with 10 wt% templates, which were dominated by a synergistic combination of the grain orientation and grain boundary density. The obvious anisotropic power factors presented, mainly coming from the texturing characteristic. A low total thermal conductivity of 1.16 W/(m·K) were greatly suppressed by tuning broad wavelength phonon scattering, which was ascribed to the layered nanostructures at grain boundaries. Furthermore, the ZT value of 0.31 was obtained at 1073 K for the sample perpendicular to pressure direction, yielding 138 % enhancement compared with that of the other direction. The work confirmed clear evidence that the textured ceramics with template seeds addition have a great influence on thermoelectricity in oxides materials. [ABSTRACT FROM AUTHOR]

It is well known that carbon addition enhances the strength of steel, but it also increases the sensitivity to delayed fracture. The origin of the increased sensitivity to delayed fracture at higher carbon content is not clarified yet. In this study, high-strength steels with different carbon contents were fabricated, and their delayed fracture properties were evaluated. As the amount of carbon in the material increased, the carbon concentration at the grain boundary (GB) and the dislocation density also increased, and the material became more sensitive to delayed fracture. Subsequently, a GB model was developed on the basis of the samples used in the experiments, and the effect of hydrogen on the GB cohesive energy was evaluated using first-principles calculations. The cohesive energy without carbon atoms was 3.47 J/m² in the presence of hydrogen, whereas that with one additional carbon atom was 3.70 J/m². This result is inconsistent with the experimental results. Therefore, based on the dislocation density measurements, we assumed that more vacancies are generated in materials with higher carbon content. By adding a vacancy at the GB, the cohesive energy decreased to 1.79 J/m² and exhibited the same tendency as in the experiment. This suggests that not only hydrogen and carbon atoms but also vacancies are responsible for a decrease in delayed fracture resistance. [ABSTRACT FROM AUTHOR]

Uranium silicide (U3Si2) is regarded as a viable fuel option for improving the safety of nuclear power plants. In the present work, phase-field simulations were employed to investigate grain growth phenomena, encompassing both isotropic and anisotropic grain growth. In simulations of isotropic grain growth, it is commonly assumed that the energy and mobility of the grain boundaries (GBs) remain constant, represented by average values. The calculated grain growth kinetic rate constant, K, exhibits a close correspondence with the experimental measurements, indicating a strong agreement between the two. In simulations of anisotropic grain growth, the values of GB energy and mobility are correlated with the angular disparity between GBs. The simulation results demonstrated that the growth rate of U3Si2 can be influenced by both the energy anisotropy and mobility anisotropy of GBs. Furthermore, the anisotropy in mobility results in a greater prevalence of low-angle GB distribution in comparison to high-angle GBs. However, the energy anisotropy of GBs does not impact the frequency distribution of the angle difference between GBs. [ABSTRACT FROM AUTHOR]

Mixed‐halide perovskites show promising applications in tandem solar cells owing to their adjustable bandgap. One major obstacle to their commercialization is halide phase segregation, which results in large open‐circuit voltage deficiency and J‐V hysteresis. However, the ambiguous interplay between structural origin and phase segregation often results in aimless and unspecific optimization strategies for the device's performance and stability. An atomic scale is directly figured out the abundant Ruddlesden‐Popper anti‐phase boundaries (RP‐APBs) within a CsPbIBr2 polycrystalline film and revealed that phase segregation predominantly occurs at RP‐APB‐enriched interfaces due to the defect‐mediated lattice strain. By compensating their structural lead halide, such RP‐APBs are eliminated, and the decreasing of strain can be observed, resulting in the suppression of halide phase segregation. The present work provides the deciphering to precisely regulate the perovskite atomic structure for achieving photo‐stable mixed halide wide‐bandgap perovskites of high‐efficiency tandem solar cell commercial applications. [ABSTRACT FROM AUTHOR]

Cathodoluminescence and electron backscatter diffraction have been applied to exactly the same grain boundaries (GBs) in a Cu(In,Ga)S2 solar absorber in order to investigate the influence of microstructure on the radiative recombination behaviour at the GBs. Two different types of GB with different microstructure were analysed in detail: random high angle grain boundaries (RHAGBs) and Σ3 GBs. We found that the radiative recombination at all RHAGBs was inhibited to some extent, whereas at Σ3 GBs three different observations were made: unchanged, hindered, or promoted radiative recombination. These distinct behaviours may be linked to atomic-scale grain boundary structural differences. The majority of GBs also exhibited a small spectral shift of about ±10 meV relative to the local grain interior (GI) and a few of them showed spectral shifts of up to ±40 meV. Red and blue shifts were observed with roughly equal frequency. [ABSTRACT FROM AUTHOR]

A phase-field model for the precipitation of Fe-Cr-Al alloy is established incorporating grain boundary (GB) effects and irradiation-accelerated diffusion. The radiation source and grain boundary effect are incorporated to broaden the applicability of the Fe-Cr-Al precipitated phase-field model. The model is firstly employed to simulate the precipitation of the Cr-rich α' phase in a single-crystal alloy. The precipitation rate and the size distribution of the precipitated phase were analyzed. Subsequently, the model is utilized to simulate segregation at GBs in a double-crystal system, analyzing the enrichment of Cr and depletion of Al near these boundaries. The simulation results are consistent with experimental observations reported in the references. Finally, the model is applied to simulate the precipitation in a polycrystalline Fe-Cr-Al system. The simulated results revealed that the presence of GBs induces the formation of localized regions with enhanced Cr and Al content as well as depleted zones adjacent to these boundaries. GBs also diminish both the quantity and precipitation rate of the formed phase within the grains. [ABSTRACT FROM AUTHOR]

Nanolayers of MoS2 can be grown to be used as active elements in nano-optoelectronic devices such as two-dimensional (2D) light emitters and optical detectors. The growth of 2D flakes might result in the formation of not only isolated triangles but also complex polycrystal flakes when different flakes interact during their in-plane expansion. In this paper, we investigate how monolayer MoS2 flakes of different shapes are affected by the biaxial strain resulting from the cooling process after chemical vapor deposition growth. The single- and polycrystal flakes are characterized at the nanoscale level by correlating morphological, electrical, and optical measurements and imaging. The main focus is given to the analysis of the exciton/trion photoluminescence (PL) components extracted from the spectra at different areas of the flake surface. According to the Raman imaging, the whole flake has built-in heterogeneous tensile strain, with the perimeter and the grain boundaries between the single-crystal parts of the poly flakes exhibiting a lower strain level (0.2–0.3%) and the central area being more strained (∼0.4%). At the perimeter and grain boundaries, the PL undergoes the strain-related blueshift accompanied by a weakening of the contribution of the long-wave trion to the spectrum and the trion binding energy. The trion formation is known to be proportional to a local electron concentration. The trion PL imaging compared to the surface potential mapping confirms a decrease in n-doping at the perimeter and grain boundaries, leading to the trion weakening. To confirm the results of electron drift to strained areas of the flake, creating the trion, the band bending at the tensile-strained flake has been theoretically calculated and modeled. The effect of edge defects at the perimeter and grain boundaries on the doping, which leads to the enhancement or inhibition of the trion formation depending on the edge and grain boundary interface type, is also discussed. [ABSTRACT FROM AUTHOR]

Two-dimensional SiC has been successfully prepared in an experiment (Phys. Rev. Lett2023,130, 076203), which provides new material candidates for power devices. In this work, molecular dynamics simulations are employed to investigate the tunable thermal transport properties of the SiC monolayer by grain boundaries (GBs). The thermal conductivity of SiC shows a pronounced dependence on the number and angle of the GBs interfaces. The inherent pentagon-heptagon structure at GBs induces atomic forces between atoms at the GBs, leading to a certain out-of-plane displacement of these atoms at the interface. Appropriate external strain can flatten the GB interface, thereby enhancing the thermal conductivity. However, further increasing the strain will decrease the thermal conductivity due to enhanced phonon anharmonicity. Moreover, the interface thermal conductance at the GBs also exhibits obvious dependence on the angle of GBs and temperature, which is explained by the atomic stress at the GBs interface. Furthermore, using phonon packet analysis, we found that the phonon interface scattering at GBs differs from that in the two-dimensional heterostructure. This finding reveals the intrinsic thermo-mechanical coupling mechanism governing thermal conduction in two-dimensional SiC, also suggesting its application in thermal management in the thermo-mechanical sensor. [ABSTRACT FROM AUTHOR]

Proton exchange membrane water electrolysis (PEMWE) is considered a promising technology for coupling with renewable energy sources to achieve clean hydrogen production. However, constrained by the sluggish kinetics of the anodic oxygen evolution reaction (OER) and the acidic abominable environment render the grand challenges in developing the active and stable OER electrocatalyst, leading to low efficiency of PEMWE. Herein, we develop the rutile‐type IrO2 nanoparticles with abundant grain boundaries and the continuous nanostructure through the joule heating and sacrificial template method. The optimal candidate (350‐IrO2) demonstrates remarkable electrocatalytic activity and stability during the OER, presenting a promising advancement for efficient PEMWE. DFT calculations verified that grain boundaries can modulate the electronic structure of Ir sites and optimize the adsorption of oxygen intermediates, resulting in the accelerated kinetics. 350‐IrO2 affords a rapid OER process with 20 times higher mass activity (0.61 A mgIr−1) than the commercial IrO2 at 1.50 V vs. RHE. Benefiting from the reduced overpotential and the preservation of the stable rutile structure, 350‐IrO2 exhibits the stability of 200 h test at 10 mA cm−2 with only trace decay of 11.8 mV. Moreover, the assembled PEMWE with anode 350‐IrO2 catalyst outputs the current density up to 2 A cm−2 with only 1.84 V applied voltage, long‐term operation for 100 h without obvious performance degradation at 1 A cm−2. [ABSTRACT FROM AUTHOR]

The last two decades have witnessed significant progress in the development of severe plastic deformation techniques to produce ultrafine-grained materials with new and superior properties. This review examines works and achievements related to the low-temperature superplasticity of ultrafine-grained aluminum alloys. The examples are provided of the possibility to observe low-temperature superplasticity in aluminum alloys at temperatures less than 0.5 Tmelt and even at room temperature, and herein, we demonstrate the cases of achieving high ductility and high strength in aluminum alloys from processing utilizing severe plastic deformation. Special emphasis is placed on recent studies of the formation of segregations of alloying elements at grain boundaries in UFG Al alloys and their influence on the development of grain boundary sliding and manifestation of low-temperature superplasticity. In addition, the current status and innovative potential of low-temperature superplasticity in aluminum alloys are observed. [ABSTRACT FROM AUTHOR]

Herein, we report a fundamental study revealing the substantial change in magnetic and electrical properties promoted by manganese (Mn) substitution in the iron (Fe) site of double perovskite LaYFe2O6 [LaYFe2-xMnxO6; x = 0, 0.05, 0.10, and 0.15], which is prepared by the sol–gel auto-combustion method. The structural, morphological, magnetic, and electrical properties of all the samples are investigated to explore the influence of Mn in the compound. X-ray diffraction (XRD) study reveals the confirmation of phase formation with orthorhombic crystal structure having symmetries P21nm and Pbnm (small contribution). X-ray photoelectron spectroscopy (XPS) analysis corroborates the mixed valence state of Fe and Mn, while the dominancy of + 3 oxidation state can be confirmed for them. Magnetization study reveals that the transition temperature reduces drastically (~ 100 K) by the Mn substitution and approaches toward room temperature (RT). At 573 K, the maximum magnetization value enhanced up to ~ 30% by the Mn substitution. Grain boundary contribution in the electrical response is more prominent in the higher Mn content samples. The application of DC magnetic field exhibits a significant influence on the impedance spectra due to the substitution of Mn in the lattice, which corroborates the signature of magnetoelectric (ME) coupling. The presence of ME coupling is further confirmed by the direct magnetoelectric measurement. This finding along with the above RT magnetic transition could make it a feasible candidate for ME-based applications. [ABSTRACT FROM AUTHOR]

The microstructure of a linear friction welded joint of 7050 aluminum alloy was investigated through optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The analysis focused on grain boundary types, microstructure, and mechanical properties of the joint. The results reveal that fine equiaxed crystals are generated in the welded zone through dynamic recrystallization. The average grain size is 6.8 mm, with a volume fraction of large angle grain boundaries reaching 69.5%. The microstructure primarily consists of Cube {001}<100> texture, {111}<110> Brass recrystallization texture, and a small amount of copper {112}<111> deformation texture. The thermomechanically affected zone (TMAZ) presents a linear structure with an average grain size of 15.8 mm and a volume fraction of 36.1% at large grain boundary, resulting in a deformed Brass {011}<211> texture and a small amount of {236}<385> as well as {111}<110> Brass recrystallization texture. The welded joint exhibits a tensile strength of 492 MPa and a yield strength of 380 MPa, which represents 94.2% and 78.5% of the base material, respectively. Furthermore, the elongation of the joint is 10.2% and 98% of the base material, respectively. The fracture of the tensile sample is observed in the TMAZ, showing good mechanical properties with a mixed fracture mode with some degrees of ductility and brittleness. [ABSTRACT FROM AUTHOR]

Amorphous Li 3 PS 4 , Li 2.94 Mn 0.06/n PS 4 (M = Mg, Ca, Al) and Li 2.94 Ca 0.03 PS 3.94 Xy 0.06/y (X = N, I) solid electrolytes were successfully prepared by planetary ball-milling method. Their structure was investigated using XRD and Raman spectroscopy. The data obtained from complex impedance spectroscopy was analyzed to study the ionic conductivity and relaxation dynamics in the prepared samples. The data was interpreted using conductivity isotherms, electrical modulus and dielectric loss tangent. Among the samples, Li 2.94 Al 0.02 PS 4 exhibited highest ionic conductivity at 25 °C, which was about 6.6 x 10−4 Scm−1. Electrical modulus and dielectric loss tangent analysis suggested that grain boundary polarization and ionic conductivity increased with multivalence cation doping. [ABSTRACT FROM AUTHOR]

The high temperature oxidation behavior of Fe–36Ni Invar alloy in the forged billet stage and hot rolled rod stage in the compressed air atmosphere has been systematically studied. The results show that the oxide layer can be divided into the external oxide layer composed of Fe2O3, Fe3O4 and NiO, and the inner transition oxide layer composed of FeO, Fe2O3, Fe3O4 and NiO. In addition, hot rolled rod samples treated by solution and rolling have higher oxidation resistance. The mechanism of O diffusion during oxidation is analyzed, and it is found that the O atom adsorbed on the surface of the substrate diffuses into the grain along the grain boundary. The grain boundary is the optimal path for O diffusion to the interior of the material, which results in the degree of intergranular oxidation of the alloy being greater than the degree of intragranular oxidation. In summary, the oxidation resistance of Invar alloy can be improved by proper solution treatment and avoiding the formation of grain boundary cracks during production.

In this study, single-crystalline and poly-crystalline CrCoNi alloys are utilized as model systems to analyze the distinct roles of each GB and interstitial lattice sites. To effectively reveal hydrogen behavior, both electrochemical and gaseous hydrogen pre-charging methods are applied. Hydrogen content, diffusivity, and trap behaviors are quantified using thermal desorption analysis and hydrogen permeation tests, which determines (1) changes in hydrogen behavior depending on the presence of GB and (2) alterations in hydrogen behavior depending on lattice crystallographic orientation. The results indicate that GB and interstitial lattice sites exhibit comparable binding energies for hydrogen trapping. However, the introduction of GB alters the primary trapping sites from interstitial lattice sites to GB. In this case, the hydrogen content in the poly-crystalline alloy is determined by the trap site density of the primary trapping site. On the other hand, in the single-crystalline alloy, where only interstitial lattice sites exist, the crystallographic orientation of the hydrogen-charged plane is an important variable that determines hydrogen content and hydrogen diffusivity. Such insights contribute to a deeper understanding of hydrogen behavior within a more intricate microstructure, suggesting the alloy design approach to enhance resistance to HE.

Recently it was found that doped barium stannates have proton conductivity and can be used for various electrochemical applications. In this study, we investigated the effect of lutetium doping of the tin sublattice on the functional performance of oxides BaSn 1-х Lu х O 3 (х = 0, 0.05, 0.1, 0.15). Oxides with the concentration of lutetium up to 10% mol. were found to be single-phase, crystallizing in a cubic structure with a space group Pm 3 m. The lattice parameter increases linearly with the concentration of lutetium. The oxide with 15 % mol. of lutetium contains an additional phase of Lu 2 Sn 2 O 7. Electrical conductivity of the oxides was studied by the 4-probe DC method and impedance spectroscopy. Experiments were carried out in H 2 O and D 2 O - containing air atmospheres, as well as under dry air conditions. It was found that electrical conductivity of BaSnO 3 does not depend on humidity, while for Lu-doped oxides tends to decrease with increase in the humidity. Impedance data analysis has shown that change in the humidity mostly affects the grain boundary resistance. It is shown for the first time that the conductivity of BaSn 1-х Lu х O 3-δ in D 2 O-containing air is higher than in H 2 O-containing air, which was explained by the thermodynamic isotope effect. [ABSTRACT FROM AUTHOR]

This paper presents an overview of recent works on microscale mechanical and other properties of silicon nitride (Si 3 N 4) determined by microcantilever bending tests and their relationships with the processing and microstructures. We first focus on deformation behaviors and fracture strength of Si 3 N 4 single crystals. β-Si 3 N 4 single crystals are plastically deformed at room temperature under high bending stress, and the yield stress depends on the crystal orientation. The critical resolved share stress of the primary slip system is determined to be below 1.5 GPa from the yield stress. Next, we address microscale mechanical properties of Si 3 N 4 polycrystalline ceramics. Emphasis is placed on their grain-boundary strength or toughness in conjunction with intergranular glassy film (IGF) which is determined by processing parameters such as sintering additives. Assessment is made on two cases of fractures at the IGF-grain interface and that within the IGF, and in each of the cases, effects of rare earth oxide additives are discussed. In Si 3 N 4 ceramics doped with Al 2 O 3 , β-SiAlON layer forming on β-Si 3 N 4 grains enhances the microscale grain-boundary strength. Finally, we shed light on microscale property-degradation behaviors of Si 3 N 4 ceramics, including the deterioration due to the contact with molten Al and the corrosion in sulfuric acid solution. The variation of the microscale properties appears in very short periods compared to the macroscale approaches, demonstrating the advantage in terms of rapid assessment of time-dependent degradation behaviors. [ABSTRACT FROM AUTHOR]

The structural, cohesive and magnetic properties of a symmetric Σ3(70.53)[011](11-1) tilt grain boundary in pure bcc iron and with commonly used alloying elements (Si, Co, Mn, Ti, Cu, Mo, Nb, V, Cr and Ni) by means of density functional theory calculations are studied. Solubility and segregation energies were calculated for different positions of dissolved atoms. Calculations show a tendency for impurities to segregate near the boundary. It was found that the substituting Co, Cu and Ni in the layer adjacent to the boundary have an embrittling effect, while other atoms enhance the cohesion of the grains. Magnetic moments on GB atoms are significantly higher than those on bulk atoms. [ABSTRACT FROM AUTHOR]

The handling safety of high explosives, as routinely characterized by the drop-weight impact sensitivity (IS), has important repercussions on the development of explosives. Herein, the impressive low IS of β-HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane) spherulite and the corresponding desensitization mechanism are elaborated with the influential role of the grain boundary. The sensitivity was evaluated by a substantial number of IS tests using “X out of 25”, Bruceton “up and down” and high-speed photography technology. The collected data, comprising over 12 batches of samples for a total of about 400 impact tests, were analyzed as a function of the particle structure parameters. The IS was found to positively relate to the porosity calculated from Small-Angle X-ray Scattering data which semi-quantitatively reflected the grain boundary in spherulite. The investigation into the influence of shape suggests that while particle shape did contribute to desensitization, the primary factor affecting the reduction in HMX sensitivity was the presence of grain boundaries. The grain boundary strengthening and spherical envelope were found to be influential as they may be beneficial for energy de-localization, thereby mitigating localized heating. The polycrystalline spherulite with purity (>98.5%), sphericity (>80.0%) and porosity (>0.4%) carefully controlled exhibited the ignition probability of 0% and H50 of c.a. 99.0 cm, outperforming any other monocrystalline β-HMX particles. This work introduces the grain boundary as a new consideration for desensitization in energetic crystals, which has been previously underestimated but holds promise for the design of high explosives with improved handling safety.

ThMn12-type Sm(FeV)12 magnets with high coercivity (Hc) demonstrate promising potential as alternative rare-earth-lean permanent magnets. This study delves into the microstructure and magnetic properties influenced by the Sm content in the SmxFe10V2 (x = 1.4–1.9) alloy. High-density SmFe10V2 bulks were prepared through a jet-milling process, followed by high-pressure pressing and heat treatment. Upon increasing the Sm content beyond 1.6, the heat-treated bulks exhibited a predominant ThMn12 phase, accompanied by a secondary phase – Sm oxides. Additionally, Sm played a pivotal role in influencing the ThMn12 crystal structure, with the c/a value reaching the smallest in the Sm1.7Fe10V2 bulk. This change contributed to heightened anisotropy constants and Tc values. The introduction of an amorphous Sm-rich grain boundary phase, with the thickness of 1.2 nm, was observed in bulks within a specific Sm content range, influenced by the heat-treatment time. Notably, this phase was absent in bulks with insufficient or excessive Sm. The grain boundary phase had a substantial impact on improving Hc, reaching 10.6 kOe in the Sm1.7Fe10V2 bulk heat-treated for 25 min. However, Hc exhibited a gradual decrease with prolonged heat treatment, attributed to the evaporation of Sm leading to the disappearance of the grain boundary phase. This nuanced relationship underscores the importance of optimizing heat treatment conditions to harness the full potential of ThMn12-type Sm(FeV)12 magnets for enhanced Hc.

Strain sensors are sensitive to mechanical deformations and enable the detection of strain also within integrated electronics. For flexible displays, the use of a seamlessly integrated strain sensor would be beneficial, and graphene is already in use as a transparent and flexible conductor. However, graphene intrinsically lacks a strong response, and only by engineering defects, such as grain boundaries, one can induce piezoresistivity. Nanocrystalline graphene (NCG), a derivative form of graphene, exhibits a high density of defects in the form of grain boundaries. It holds an advantage over graphene in easily achieving wafer-scale growth with controlled thickness. In this study, we explore the piezoresistivity in thin films of nanocrystalline graphite. Simultaneous measurements of sheet resistance and externally applied strain on NCG placed on polyethylene terephthalate (PET) substrates provide intriguing insights into the underlying mechanism. Raman measurements, in conjunction with strain applied to NCG grown on flexible glass, indicate that the strain is concentrated at the grain boundaries for smaller strain values. For larger strains, mechanisms such as grain rotation and the formation of nanocracks might contribute to the piezoresistive behavior in nanocrystalline graphene.

Mixed‐conducting perovskites are workhorse electrochemically active materials, but typical high‐temperature processing compromises their catalytic activity and chemo‐mechanical integrity. Low‐temperature pulsed laser deposition of amorphous films plus mild thermal annealing is an emerging route to form homogeneous mixed conductors with exceptional catalytic activity, but little is known about the evolution of the oxide‐ion transport and transference numbers during crystallization. Here the coupled evolution of ionic and electronic transport behavior and structure in room‐temperature‐grown amorphous (La,Sr)(Ga,Fe)O3‐x films as they crystallize is explored. In situ ac‐impedance spectroscopy with and without blocking electrodes, simultaneous capturing‐synchrotron‐grazing‐incidence X‐ray diffraction, dc polarization, transmission electron microscopy, and molecular dynamics simulations to evaluate isothermal and non‐isothermal crystallization effects and the role of grain boundaries on transference numbers is combined. Ionic conductivity increases by ≈2 orders of magnitude during crystallization, with even larger increases in electronic conductivity. Consequently, as crystallinity increases, LSGF transitions from a predominantly ionic conductor to a predominantly electronic conductor. The roles of evolving lattice structural order, microstructure, and defect chemistry are examined. Grain boundaries appear relatively nonblocking electronically but significantly blocking ionically. The results demonstrate that ionic transference numbers can be tailored over a wide range by tuning crystallinity and microstructure without having to change the cation composition. [ABSTRACT FROM AUTHOR]

Due to its characteristic of low stress brittle fracture, hydrogen embrittlement (HE) is a great challenge for the alloys exposed to hydrogen-containing environments, threatening the safety and integrity of structural components. The physical and chemical status of the interfaces, among which grain boundary (GB), twin boundary (TB), and matrix/nano-precipitate interfaces (coherent, semi-coherent, and incoherent) are the representative ones, play a crucial role in determining the HE susceptibility of materials. Hence, this study mainly reviews recent progress in the interaction between hydrogen and these interfaces, i.e., 1) hydrogen-GB interaction (dominant HE mechanisms, crystallographic features of hydrogen-assisted intergranular cracking, and the strategies for resisting HE through GB segregation and GB engineering); 2) hydrogen-TB interaction (the effect of deformation/pre-existing twins on HE susceptibility, four types of TB-related cracking mechanisms, and the improvement of HE-tolerance by the control of pre-twins, gradient-twins, and twin orientations); and 3) hydrogen-precipitate interaction (hydrogen capacity, hydrogen trapping sites, hydrogen activation energy, and the effect of nano-precipitates on HE of alloys). The correlation between HE susceptibility, active HE mechanisms and their synergy (HELP + HEDE model), and three types of interfaces have been comprehensively summarized and discussed. Also, the strategies for the improvement of HE resistance are proposed in terms of the control of these microstructural interfaces in metallic alloys. [Display omitted] • Effect of the interfaces on hydrogen embrittlement (HE) of alloys is reviewed. • Hydrogen-assisted interface cracking mechanisms of alloys is summarized. • Strategies for resisting HE are proposed through the control of the interfaces. • Semi-coherent precipitates are suggested to balance strength and HE-resistance. [ABSTRACT FROM AUTHOR]

The atomistic simulations in this article substantiate that grain boundary stress fields remain unaffected by changes in their area, aligning with the Olson–Cohen theory which supports that such area insensitivity is an inherent outcome of the combined effect of coherency and anti‐coherency dislocations. Twist grain boundaries are employed in α‐iron as a model in atomistic simulations, revealing and contrasting the dislocations and stresses of these grain boundaries when their area varies from infinity to a few square nanometers. It is discovered that the grain boundary stresses remain relatively constant, always short‐ranged. Furthermore, within the framework of the Frank–Bilby equation, the line directions and spacing of coherency and anti‐coherency dislocation arrays in a grain boundary are predicted, the stresses of these dislocations are subsequently calculated numerically, and these stresses are superimposed together to form the grain boundary stress field. The numerical calculations verify that stress fields of grain boundaries are not sensitive to changes of their area, corroborating our atomistic simulations. The preliminary atomistic simulations of various homophase and heterophase boundaries further affirm this area insensitivity. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrochemical CO 2 reduction reaction (CO 2 RR) presents a unique opportunity to convert carbon dioxide (CO 2) to value-added products while simultaneously storing renewable energy in the form of chemical energy. However, particle applications of this technology are limited due to the poor efficiency and product selectivity of the existing catalyst. In this study, we demonstrate a facile method for the heat-induced transformation of copper nanowires into CuO x /Cu nanotubes with defect-enriched surfaces. During this transformation, the outward migration of copper results in the formation of tubular structures encased within nanosized oxide grains. Notably, the hydrogen faradaic efficiency (FE) decreases with extended heat treatment, while carbon monoxide (CO) FE increases. As compared to Cu NWs, Cu NTs exhibit lower selectivity towards H 2 and single-carbon (C 1) products and favor the formation of multi-carbon (C 2+) products. Consequently, a 2-fold increase in the single pass CO 2 conversion (SPCC) and C 2+ half-cell energy efficiency (EE half cell) was noted after heat treatment. The Cu NT-4 variant, synthesized under optimized conditions, exhibits the highest FE of 72.1 % for C 2+ products at an operating current density (I D) of 500 mA cm−2. [ABSTRACT FROM AUTHOR]

Aluminum-incorporated medium-manganese steel (MMnS) has potential for lightweight transport applications owing to its impressive mechanical properties. Increasing the austenite volume fraction and making microstructural changes are key to manufacturing MMnS. However, the grain boundary character and strain distribution of intercritically annealed low-density MMnS have not been extensively scrutinized, and the effects of crystallographic texture orientation on tensile properties remain ambiguous. Therefore, in this study, the microstructure, microtexture, strain distribution, and grain boundary characteristics of a hot-rolled medium-Mn steel (Fe–0.2 C–4.3 Al–9.4 Mn (wt%)) were investigated after intercritical annealing (IA) at 750, 800, or 850 °C for 1 h. The results show that the 800 °C annealed sample exhibited the highest austenite volume fraction among the specimens (60%). The duplex microstructure comprised lath-type γ-austenite, fine α-ferrite, and coarse δ-ferrite. As the IA temperature increased, the body-centered cubic phase orientation shifted from <001> to <111>. At higher temperatures, the face-centered cubic phase was oriented in directions ranging from <101> to <111>, and the sums of the fractions of high-angle grain boundaries and coincidence–site–lattice special boundaries were significantly increased. The 800 °C annealed sample with a high austenite content and strong γ-fiber {111}//RD orientation demonstrated a noteworthy tensile strength (1095 MPa) and tensile elongation (30%). [ABSTRACT FROM AUTHOR]

Grain boundary (GB) precipitation-induced cracking is a significant issue for S31254 super austenitic stainless steel during hot working. Investigating the deformation behavior based on precipitate morphology and distribution is essential. In this study, continuous smaller and intermittent larger precipitates were obtained through heat treatments at 950 °C and 1050 °C. The microstructure evolution and mechanical properties influenced by precipitates were experimentally investigated using an in situ tensile stage inside a scanning electron microscope (SEM) combined with electron backscatter diffraction (EBSD). The results showed that continuous precipitates at 950 °C had a stronger pinning effect on the GB, making grain rotation difficult and promoting slip deformation in the plastic interval. Continuous precipitates caused severe stress concentration near GB and reduced coordinated deformation ability. Additionally, the crack propagation path changed from transcrystalline to intercrystalline. Furthermore, internal precipitates were a crucial factor affecting the initial crack nucleation position. Interconnected precipitates led to an intergranular fracture tendency and severe deterioration of the material's plasticity, as observed in fracture morphology. [ABSTRACT FROM AUTHOR]

Low‐temperature polycrystalline silicon (LTPS) thin‐film transistor devices can be used as core components of pixel driving circuits for active matrix organic light‐emitting displays （AMOLED）. Poly silicon (P‐Si) film and device performance directly affects the display effect. This paper investigates polysilicon grain boundary reduction for LTPS devices on PI substrates, exploring the effects of grain boundary reduction on LTPS devices and image sticking. Reduction of polysilicon grain boundaries through optimization of a‐Si deposition process, a‐Si two‐step deposition and excimer laser annealing (ELA) doublescan process, ELA double‐scan process reduces grain boundaries by 67 %. We prepared LTPS devices with thinner gate interlayers (GI) based on P‐Si grain boundary reduction, LTPS devices with positive threshold voltage bias and increased mobility, AMOLED displays with thinner GI can have 23% better image sticking. [ABSTRACT FROM AUTHOR]

The well-known de Gennes analogy between smectics and superconductors predicts two types of smectic A behaviour under imposed bend. In Type I smectics, the smectic order melts, expelling all of the bend in a bulk nematic region (3D 'defect'). In Type II smectics, the order melts on 1D defects, edge dislocation lines, which form an Abrikosov-like lattice. Here, I discuss how the strong anisotropy of the smectic coherence lengths influence the smectic A behaviour under imposed bend distortion. I show analytically and numerically that, as proposed previously, a third type of behaviour is possible close to a second-order nematic–smectic A transition, with smectic order melting on the plane of the grain boundary (2D defects). This third kind of behaviour, Melted Grain Boundary (MGB), which has been previously reported experimentally in the smectic A material 9CB, is intermediate between the Type I and Type II behaviours and can be considered as Type 'one-and-a-half' smectic A. I define the domain of material parameters in which the planar MGB defect is energetically and topologically stable. I discuss also if similar planar defects may exist, or not, in other anisotropic materials, e.g. superconductors, chiral smectic A, cholesterics and twist-bend nematics. [ABSTRACT FROM AUTHOR]

The manufacturing process for wrought Ti alloys with the hexagonal close-packed (HCP) structure introduces a complicated microstructure with abundant intra- and inter-grain boundaries, which greatly influence performance. In the hexagonal close-packed (HCP) structure, two types of grain boundaries are commonly observed between grains with ~90° misorientation: the basal/prismatic boundary (BPB) and the coherent twin boundary (CTB). The mechanical response of the BPB and CTB under external loading was studied through molecular dynamic simulations of HCP-Ti. The results revealed that CTB undergoes transformation into BPB through the accumulation of twin boundary (TB) steps and subsequent emission of Shockley partial dislocations. When the total mismatch vector is close to the Burgers vector of a Shockley partial dislocation, BPB emits partial dislocations and further grows along the stacking faults. When a pair of CTBs are close to each other, severe boundary distortion occurs, facilitating the emission and absorption of partial dislocations, which further assists the CTB-BPB transformation. The present results thus help to explain the frequent observation of coexisting CTB and BPB in HCP alloys and further contribute to the understanding of their microstructure and property regulation. [ABSTRACT FROM AUTHOR]

Granite is a heterogeneous material characterized by a significant population of mechanically distinct grain boundaries, which exert a substantial influence on crack propagation. An extended grain-based model was developed by integrating the geometric heterogeneity, represented by Voronoi tessellations, and the mechanical heterogeneity of grain boundary, as described by Weibull distribution. This study numerically investigates the influence of mechanical heterogeneity in grain boundary on the mechanical properties and microcracking behavior of semi-circular bend granite samples under mode I loading. The mechanical heterogeneity of grain boundary was assessed by independently varying the heterogeneity index, defined by the shape parameter m in the Weibull distribution. The findings indicate that the force–displacement curve and fracture toughness are primarily influenced by the parallel bond tensile strength and cohesion of grain boundary contacts. When the value of m in Weibull distribution is between 1.5 and 2, a compromise between failure patterns and diverse grain boundaries characterization can be reached. Considering the heterogeneous mechanical properties of grain boundary numerically is able to simulate the local stress concentration of the real rocks, thus accelerating the generation of microcracks and reflecting the brittleness of rock failure. Otherwise, the fracture toughness of the rock will may be overestimated. Generally speaking, models that consider grain boundary heterogeneity will produce larger fracture process zone and microscopically complex crack propagation patterns during loading, and these phenomena are more consistent with experimental observations than those models in which grain boundaries are homogeneous. Highlights: The mechanical heterogeneity of grain boundary in granite is quantitatively characterized by the Weibull distribution; The heterogeneous grain boundary could favor the local stress concentration, thus accelerating the generation of microcracks; Considering both geometric heterogeneity of granite and mechanical heterogeneity of grain boundary result in the generation of larger fracture process zone and microscopically complex crack propagation patterns under mode I loading. [ABSTRACT FROM AUTHOR]

The upconversion fluorescence thermometry has been recognized as one of the most promising techniques for the temperature measurement and multi-mode fluorescence temperature sensing can improve the accuracy and widen the temperature range. Herein, a fluorescence thermometry was developed based on the MgAlON: Er3+ transparent ceramic. It was demonstrated that the enrichment of Er3+ in grain boundaries increased susceptibility to temperature variations of the cross-relaxation rate, which endowed the non-thermally coupled energy levels with temperature sensing properties and led to the multi-mode thermometric capability. A novel four-mode temperature sensor based on fluorescence intensity ratios (2H 11/2 /4S 3/2 and 4F 9/2 /4S 3/2) and fluorescent lifetimes (4F 9/2 and 4S 3/2) was realized in the temperature range of 180–500 K, which brought about the maximum absolute and relative sensitivities reached 0.0258 K−1 and 2.95% K−1, respectively. This work reveals that the MgAlON: Er3+ and the grain boundary functionalization of transparent ceramics could have potential applications for fluorescence thermometry. • A novel four-mode MgAlON: Er3+ fluorescent temperature sensor was prepared. • The maximum absolute and relative sensitivities of MgAlON: Er3+ reached 0.0258 K−1 and 2.95% K−1, respectively. • The grain boundary enrichment of Er3+ makes the cross-relaxation rate temperature-sensitive, forming a multi-mode fluorescence thermometry. [ABSTRACT FROM AUTHOR]

Processing of materials using electrical field presents an important research and engineering field. It allows to process materials at less demanding conditions, synthesize new phases and compositions. Herein, nanocrystals of CeO 2 were synthetized and grown in-situ under AC and DC electrical fields. Main crystallographic properties like crystallite size, morphology texture and grain boundaries were significantly influenced by the electrical field up to 600 °C. Above this temperature, the thermally driven grain growth hindered the electrical field effect and led to a common behavior, isotropic particle shape and surface properties. This can be linked to the electrical and thermal force competition for the grain boundary development. To our knowledge such comprehensive description of the field effect on the growth of nanocrystals and its limitations has never been reported and can open a new door for processing of nanocrystalline materials. [Display omitted] [ABSTRACT FROM AUTHOR]