Distortion Of Crystal Structure Research Articles

Promoted room temperature NH3 gas sensitivity using interstitial Na dopant and structure distortion in Fe0.2Ni0.8WO4.

The demand for gas-sensing operations with lower electrical power and guaranteed sensitivity has increased over the decades due to worsening indoor air pollution. In this report, we develop room-temperature operational NH3 gas-sensing materials, which are activated through electron doping and crystal structure distortion effect in Fe0.2Ni0.8WO4. The base material, synthesized through solid-state synthesis, involves Fe cations substitutionally located at the Ni sites of the NiWO4 crystal structure and shows no gas-sensing response at room temperature. However, doping Na into the interstitial sites of Fe0.2Ni0.8WO4 activates gas adsorption on the surface via electron donation to the cations. Additionally, the hydrothermal method used to achieve a more than 70-fold increase in the surface area of structure-distorted Na-doped Fe0.2Ni0.8WO4 powder significantly enhances gas sensitivity, resulting in a 4-times increase in NH3 gas response (Rg/Ra). Photoluminescence and XPS results indicate negligible oxygen vacancies, demonstrating that cation contributions are crucial for gas-sensing activities in Na-doped Fe0.2Ni0.8WO4. This suggests the potential for modulating gas sensitivity through carrier concentration and crystal structure distortion. These findings can be applied to the development of room-temperature operational gas-sensing materials based on the cations.

Degree of Crystal Structure Distortion-Induced Tunable LiGaO2 Long Persistent Luminescence for Optical Information Encryption.

Tunable long persistent luminescence (LPL) phosphor materials have great potential for optoelectronic cryptographic applications. However, the mainstream techniques of modulating LPL generally have the characteristics of complex preparation processes, demanding crystal field environments, or expensive dopant ions, which restrict large-scale commercial application. Herein, we develop a simple, high-efficiency, and low-cost strategy to optimize the LPL of LiGaO2(LGO):Cu2+ by changing the sintering time to regulate the degree of crystal structure distortion. The Cu2+ as charge compensation will substantially enhance the emission intensity of LGO by a factor of 11.02 originating from the appropriate ionic size and coordination mode. Besides, the LPL time of LGO:Cu2+ can be extended effectively to 2 h by adjusting the sintering temperature and time (900 °C@24 h). The extension mechanism is that Li and Ga can be substituted for each other more easily and induce crystal structure distortion due to the special crystal structure of LGO, resulting in an optimal trap concentration in LGO:Cu2+. Thus, our findings provide a simple way to modulate long persistent luminescence and further consider their potential impact on optical information encryption.

Influence of Nb Doping on the Performance of Oxygen Reduction Reaction on TiO2 in Acidic Environmental

Polymer electrolyte fuel cells (PEFCs) have attracted attention as one of the next-generation power sources that are environmentally friendly. However, the high manufacturer's costs, short service life, and insufficient cell performance are solved to realize widespread commercialization. A non-platinum group metal catalyst is relatively low in cost and highly durable. In particular, the oxides of group 4 and 5 elements were reported to show high oxygen reduction reaction (ORR) activity and durability. Their oxides are considered dominant candidates for the non-platinum group metal catalysts, although they have a fateful flaw that their ORR activity is clearly poorer than traditional platinum-supported carbon catalysts. It was reported that introducing oxygen vacancies and other transition metals into the crystal structure of 4- and 5-group metal oxides effectively enhanced the ORR activity. The active site of 4- and 5-group metal oxides is unclear despite it being well-known that the oxygen vacancies and dopant atoms are related to its ORR activity. It is now indicated that candidates of active site were the oxygen vacancies around the dopant atom and the crystal distortion. However, it is hard to separate their effects because both dopant atoms and oxygen vacancies distort the local crystal structure. On the other hand, identifying the ORR active site leads to obtaining the catalyst design with high ORR activity. We focused on the oxide nanosheet, the simplest structure formed by a six-coordinate octahedral, as the model electrode. The thickness of oxide nanosheets is about 1 nm, and forming a single layer on a substrate is relatively easy. Thus, it was expected that the electron conductivity was guaranteed enough by the tunnel effect. This study employed titanium oxide nanosheets (TiO2ns) as the model catalyst and niobium as a dopant to investigate the effect of dopant atoms on ORR activity. The ratio of Nb/Ti in the prepared model electrode was 0/1, 1/1, and 2/1. In addition, the oxygen vacancies were introduced into all prepared electrodes to study the impact of oxygen vacancies on ORR activity at each Nb/Ti ratio. The thickness of Nb-doped TiO2ns (Nb-TiO2ns) was about 1.2 nm for the 1/1 ratio and slightly thicker for the 0/1 ratio. In contrast, the thickness of the 2/1 ratio of Nb-TiO2ns was about two times thicker than the 1/1 ratio. The thicknesses of Nb-TiO2ns in each ratio were increased by the reduction treatment to introduce the oxygen vacancies. One reason for this thickness increase may be related to the phase transition into the anatase structure. ORR activity was evaluated from the on-set potential of ORR (E ORR) measured at the step scan with 3 minutes step width. E ORR was slightly elevated with Nb doping. The ion radii of Nb and Ti atoms are 3 pm different when it is assumed that both ions are six-coordinated and their valence is Nb5+ and Ti4+. These results showed that the crystal structure distortion probably has a slight but positive effect on ORR activity.After the reduction treatments, the E ORR of the 0/1 ratio of Nb-TiO2ns increased and was the same as that of the 2/1 ratio. The introduction of oxygen vacancies certainly enhanced the ORR activity of the 0/1 ratio of Nb-TiO2ns. The oxygen vacancies are thought to be necessary to enhance the ORR activity, although the reduction condition wasn’t optimized for the Nb-doped samples.From the above results, we consider that the active site is the oxygen vacancy site rather than the crystal distortion site at this time.

Active site modulation in UiO-66(Ce) MOFs by Al3+ doping for boosting photocatalysis

A series of Al3+-doped UiO-66(Ce) MOFs (U(CexAl1−x)) was developed to reveal the roles of metal doping on active site formation and substrate activation in photocatalytic selective transformation of amines to imines. Al3+ doping induced crystal structure distortion to form coordinately unsaturated metal (Al, Ce) sites as Lewis acid sites to chemisorb and activate benzylamine (BA). In situ FTIR revealed that the Al site with stronger acid strength facilitated BA activation. The activation degree of N–H bonds in BA was evaluated by changes of calculated force constant. The intermediate products were confirmed through time-dependent in situ FTIR. The Al3+-doped sample U(Ce0.90Al0.10), the optimal catalyst, showed a significantly increased BA conversion (97.6 %) than that (47.5 %) of undoped sample, which was attributed to enough active sites and the optimal charge mobility. Finally, the present study proposes a synergistic photocatalytic mechanism associated with molecular activation to demonstrate selective oxidation pathways at the molecular level.

Surface engineering of Li3V2(PO4)3-based cathode materials with enhanced performance for lithium-ion batteries working in a wide temperature range

Operating at extreme temperatures is the biggest challenge for lithium-ion batteries (LIBs) in practical applications, as both the capacity and cycling stability of LIBs are largely decreased due to the sluggish reaction kinetics of the cathodes. Therefore, developing suitable cathode materials is the key point to tackling this challenge. Lithium vanadium phosphate [Li3V2(PO4)3, LVP] is a promising cathode with good features of a high working voltage, high intrinsic ionic diffusion coefficiency, and stable olivine structure in a wide temperature range, although it is perplexed by the low electronic conductivity. To tackle this issue, a series of nitrogen-doped carbon network (NC) coated LVP composites were synthesized using a hydrothermal-assisted sol-gel method. Among them, the LVP@NC-0.8 sample exhibited a remarkable tolerance at a high charging cutoff voltage of 4.8 V in a wide temperature range. Full cells of LVP@NC-0.8||graphite exhibited superior performance at different current rates. Moreover, the reaction mechanism of the LVP@NC-0.8 electrode was proved by in-situ X-ray diffraction technique, demonstrating that temperature was a critical factor that contributed to the sluggish phase transformation with high voltage hysteresis at low temperature and severe crystal structure distortion at high temperature. Theoretical calculations further demonstrated the superiority of the NC for high electronic conductivity and reduced lithium transportation barriers. The enhanced electrochemical performances of LVP-based cathode materials have provided the possible application of LIBs in a wide temperature range.

Dielectric and magnetic response of mechanically activated Mn-doped SrTiO3 ceramics

This research was focused on the influence of manganese (Mn) incorporation at Sr and/or Ti sites on the microstructure, relative dielectric permittivity and specific magnetization of strontium titanate (SrTiO3) ceramics. A solid-state method was used for the preparation of mechanically activated (10, 30 and 120 min) Mn-doped SrTiO3 ceramics with various manganese dioxide (MnO2) weight percentages (1.5, 3 and 6 wt%). Rietveld's analysis showed that the mean crystallite size in doped-activated SrTiO3 ceramics is smaller than in undoped ceramics, which is a consequence of additional crystal structure distortion due to ion substitution. Changes in the Raman spectra indicated dopant incorporation in the SrTiO3 lattice. The microstructural analysis pointed out a decrease in the mean grain size with increasing dopant concentration and time of activation. The highest values of permittivity and magnetization were observed for Mn-doped SrTiO3 ceramic mechanically activated for 120 min. Based on all the above, the optimal electrical and magnetic properties of SrTiO3 ceramics can be achieved by the appropriate choice of mechanical activation time and dopant concentration.

Mixed cations tin-germanium perovskite: A promising approach for enhanced solar cell applications

Significant progress has been made over the years to improve the stability and efficiency of rapidly evolving tin-based perovskite solar cells (PSCs). One powerful approach to enhance the performance of these PSCs is through compositional engineering techniques, specifically by incorporating a mixed cation system at the A-site and B-site structure of the tin perovskite. These approaches will pave the way for unlocking the full potential of tin-based PSCs. Therefore, in this study, a theoretical investigation of mixed A-cations (FA, MA, EA, Cs) with a tin-germanium-based PSC was presented. The crystal structure distortion and optoelectronic properties were estimated. SCAPS 1-D simulations were employed to predict the photovoltaic performance of the optimized tin-germanium material using different electron transport layers (ETLs), hole transport layers (HTLs), active layer thicknesses, and cell temperatures. Our findings reveal that EA0.5Cs0.5Sn0.5Ge0.5I3 has a nearly cubic structure (t = 0.99) and a theoretical bandgap within the maximum Shockley-Queisser limit (1.34 eV). The overall cell performance is also improved by optimizing the perovskite layer thickness to 1200 nm, and it exhibits remarkable stability as the temperature increases. The short-circuit current density (Jsc) remains consistent around 33.7 mA/cm2, and the open-circuit voltage (Voc) is well-maintained above 1 V by utilizing FTO as the conductive layer, ZnO as the ETL, Cu2O as the HTL, and Au as the metal back contact. This configuration also achieves a high fill factor ranging from 87 % to 88 %, with the highest power conversion efficiency (PCE) of 31.49 % at 293 K. This research contributes to the advancement of tin-germanium perovskite materials for a wide range of optoelectronic applications.

Mechanistic insights into temperature hysteresis in CO oxidation on Cu-TiO2 mesosphere

This study employs in-situ X-ray absorption spectroscopy (XAS) and operando Raman to explore the reaction mechanism of copper/titanium dioxide microspheres (CuTMS) in CO oxidation. A temperature-dependent hysteresis behavior was observed during catalytic CO oxidation, which can be divided into two distinct regions. In the low-temperature region, the transformation of CuO → Cu2O → Cu2O/Cu on the surface of CuTMS is detected via in-situ XAS, highlighting the pivotal role of surface-adsorbed oxygen in initiating this conversion process. Conversely, in the high-temperature region, analysis of Raman peak areas suggests a variation in the {001} and {101} facets of anatase. Specifically, a decrease in the {001} facets from 17% to 10% indicates TiO2-mediated oxygen transportation, which facilitates the reoxidization of reduced Cu species. This integrated approach showcases significant potential for unraveling the mechanistic studies of catalytic reaction mechanisms in copper/titanium systems, including surface copper valence state changes, oxygen replenishment, and crystal structure distortion.

Balancing electron transfer and intermediate adsorption ability of metallic Ni-Fe-RE-P bifunctional catalysts via 4f-2p-3d electron interaction for enhanced water splitting

Balancing electron transfer and intermediate adsorption ability of bifunctional catalysts via tailoring electronic structures is crucial for green hydrogen production, while it still remains challenging due to lacking efficient strategies. Herein, one efficient and universal strategy is developed to greatly regulate electronic structures of the metallic Ni-Fe-P catalysts via in-situ introducing the rare earth (RE) atoms (Ni-Fe-RE-P, RE = La, Ce, Pr, and Nd). Accordingly, the as-prepared optimal Ni-Fe-Ce-P/CC self-supported bifunctional electrodes exhibited superior electrocatalytic activity and excellent stability with the low overpotentials of 247 and 331 mV at 100 mA cm−2 for HER and OER, respectively. In the assembled electrolyzer, the Ni-Fe-Ce-P/CC as bifunctional electrodes displayed low operation potential of 1.49 V to achieve a current density of 10 mA cm−2, and the catalytic performance can be maintained for 100 h. Experimental results combined with density functional theory (DFT) calculation reveal that Ce doping leads to electron decentralization and crystal structure distortion, which can tailor the band structures and d-band center of Ni-Fe-P, further increasing conductivity and optimizing intermediate adsorption energy. Our work not only proposes a valuable strategy to regulate the electron transfer and intermediate adsorption of electrocatalysts via RE atoms doping, but also provides a deep understanding of regulation mechanism of metallic electrocatalysts for enhanced water splitting.

Cobalt molybdenum di-selenide surface modification: A path to improved trifunctional catalysis via partial oxygenation

Efficient, stable, and cost-effective electrocatalysts for hydrogen evolution, oxygen evolution, and oxygen reduction reactions have been in demand for decades. Recently, layered transition metals (Co, Mo, Ni, and Fe) and chalcogen compounds (S/Se/Te) gained prominence in catalysis and device studies. Density functional theory identified the covalency of Co and Mo, oxygenated bimetallic selenium bond, crystal structure distortions, and adsorption properties as crucial for enhanced electrocatalytic activity. Hybridizing the Co and Mo d-orbitals around the Fermi level of 0.463 eV improves bonding with metal surface-adsorbate intermediates validated by partial density of states. Oxygenated cobalt molybdenum selenide (O-CoMoSe2) (210) exhibited remarkable electrocatalytic properties at various active sites, with Gibbs free energy and theoretical overpotential at an active site of Co = 0.086 eV, 0.41 V, and Se = 0.50 V.

Enhanced ferromagnetic properties achieved by F-doping in BaFe1-xMnxO3-δ.

Tailoring the crystal structure, spin, and charge state of perovskite oxides through fluorine ion doping is an attractive and effective strategy, which could significantly modify the physical and chemical properties of base oxides. Here, BaFe1-xMnxO3-δ (x = 0, 0.1, 0.2, 0.3) and BaFe1-xMnxO2.9-δF0.1 (x = 0.1, 0.2, 0.3), belonging to 6H-type BaFeO3-δ, are prepared and investigated to evaluate the impact of F- doping. The distortion of crystal structure and the reduced average valence of Mn and Fe confirm the preference for F- substitution in the hexagonal layer, which are found as the key factors for the improved magnetic properties, including ferromagnetic ordering temperature, coercive force, and remanent magnetization. Moreover, the valence reduction of B-site ions and the increased resistance distinctly indicate the expense of electron hole via fluorine doping. This work describes the adjustment of crystal structure, electronic configuration, and ferromagnetic performance by simple F- doping, which provides a prospect for practical magnetic materials.

Crystal symmetry transition and its influence on optical, dielectric, and ferroelectric properties in (1-x)Na0.5Bi0.5TiO3-xSrTiO3 system

Ferroelectric perovskites materials are the most promising materials because of their multifunctional applications as well as the ongoing fundamental research on them. The present study investigates the correlation between the crystal structure and various physical properties such as dielectric, ferroelectric, and optical properties of Sr2+ modified Sodium bismuth titanate Na0.5Bi0.5−xSrxTiO3 (x = 0.00, 0.02, 0.04, and 0.06) synthesized by solid-state reaction method. Rietveld refinement of the X-ray diffraction pattern reveals that the system undergoes a crystal symmetry transition from a two-phase crystal symmetries system (rhombohedral (R3c) and tetragonal (P4bm)) to a three-phase crystal symmetries system (rhombohedral (R3c), tetragonal (P4bm) and Cubic (Pm3̅m)) with the rise in Sr2+ concentration in Na0.5Bi0.5−xSrxTiO3 which is the foremost reason behind the variation of physical properties of the system. The dielectric constant and maximum polarization increase with the Sr2+ concentration up to 2% and it decreases with the further increase in Sr concentration due to the distortion in crystal structure induced by the introduction of cubic phase (Paraelectric) in the system. The maximum value of the dielectric constant is estimated to be 3629 at a low frequency on the Na0.50Bi0.48Sr0.02TiO3 system. The optical band gap (Eg) of Na0.5Bi0.5−xSrxTiO3 (x = 0.00, 0.02, 0.04, and 0.06) ceramics are found to vary between 3.202 eV to 3.172 eV which indicates the semiconducting nature of prepared samples but urbach energy shows an opposite behaviour i.e. increases with Sr concentration.

ZnVO3: an ilmenite-type vanadium oxide hosting robust V-V dimers.

Ilmenite-type vanadium oxides exhibit a distinctive cation-dimerization behavior. Here, we report a novel ilmenite-type compound, ZnVO3. Polycrystalline ZnVO3 samples are synthesized under conditions of 10 GPa and 1573 K. The obtained sample crystallizes in the triclinic P1̄ space group. Both V-V and Zn-Zn dimers (dimer-like displacement) are present in the structure, arranged in a ladder-like pattern on each honeycomb lattice. Notably, the V-V dimer persists up to 625 K, surpassing the stability of the V-V dimer state in other ilmenite-type vanadium oxides. Magnetic susceptibility measurements corroborate the formation of direct V-V bond in the dimer. The off-centered position of the Zn2+ ion at the octahedral site, driven by Zn-O covalency and its sp3 nature, promotes the Zn-Zn dimer-like displacement. Cooperative distortions between honeycomb layers further reinforce the V-V dimers. This finding offers insights into controlling cation-dimer strength in crystalline compounds via crystal structure distortions.

Solidification/stabilization and immobilization mechanism of Pb(II) and Zn(II) in ettringite

Ettringite, as the dominant hydration product in cement materials, plays a significant role in the solidification/stabilization of heavy metals. However, the combination and immobilization mechanism of heavy metal ions in ettringite crystals have yet to be fully understood. In this study, ettringite crystals were synthesized using the solution reaction method to investigate the adsorption and chemical encapsulation reactions of Pb2+ and Zn2+. In addition, the microstructures of the ettringite crystals doped with heavy metals were characterized by XRD, FTIR and SEM/EDS to elucidate the immobilization mechanism of Pb2+ and Zn2+ on ettringite crystals. The results indicated that ettringite has a high specific surface area of 64.456 m2/g and considerable mesopore and macropore volumers. The optimal adsorption efficiency of Pb2+ and Zn2+ in ettringite, accounting for 98.7 % and 99.9 %, respectively, was realized in an initial liquid with a pH of 10. The adsorption kinetics results showed that the equilibrium adsorption capacities of Pb2+ and Zn2+ were 196.04 and 185.57 mg/g, respectively. In addition, the adsorption reaction of Pb2+ in ettringite was predominantly characterized by a chemisorption process; whereas the adsorption reaction of Zn2+ in ettringite was characterized by the simultaneous action of physisorption and chemisorption. The multi-peaks Gaussian fitting curves of the FTIR patterns indicated that Pb2+ and Zn2+ promoted the formation of ettringite and induced more H-O-H groups. Moreover, this study proposed and confirmed that significant differences exist between the immobilization mechanisms of Pb2+ and Zn2+ in ettringite. The lattice constant and coordination chemistry analysis revealed that Pb2+ mainly substituted Ca2+ and Al3+ in ettringite via lattice substitution. In contrast, Zn2+ predominantly induced some lattice distortion in the ettringite crystal structure and formed a solid solution via interstitial doping. Furthermore, the micro channel architecture and hydrogen bond network significantly contributed to the adsorption and solidification of heavy metals. Overall, the chemical bonding mechanism was more prominent for the solidification of Pb2+ than that of Zn2+ in ettringite, and ettringite exhibited a superior adsorption capacity and stronger binding affinity for Pb2+.

Doping induced phase stabilization and electronic properties of alkaline earth metal doped zirconium (IV) oxide: A first principles study

The role of divalent dopant cations such as Ca and Mg in phase stabilization of ZrO2 has been demonstrated experimentally, with Mg emerging as a crucial dopant ion because of its ability to enhance the photocatalytic properties of ZrO2. To provide a theoretical basis for these experimental observations, the modifications of the crystal and electronic structure of the monoclinic phase of zirconia, m-ZrO2, upon doping with Mg have been studied at the atomic level using Density Functional Theory method. Additionally, the effect of dopant ionic radius on the electronic properties has been demonstrated by doping with Ca, which is isoelectronic with Mg. On 6.25 % doping, a structural distortion of the monoclinic crystal structure towards a tetragonal structure is observed. Additionally, the Density of States of doped m-ZrO2 exhibits the characteristics of t-ZrO2 in the Zr d orbitals in the unoccupied states and O unoccupied states emerge upon creation of an O vacancy in Mg/Ca doped m-ZrO2. The calculated band gap of m-ZrO2 is 3.6 eV. Upon doping there is a shift of the Fermi energy towards the valence band maximum.

Gd-doped BiFeO3 crystalline nanofibers for efficient rhodamine B in wastewater removal under simulated sunlight

This work synthesized a series of Gd-doped BiFeO3 (BGFO) hollow nanofibers by electrostatic spinning technique. The wall thickness of the hollow nanofibers was about 100 nm with an average grain size of 20 nm. The crystal structure distortion was found, and the BiFeO3 coexisted with rhombohedral and orthorhombic phases. The degradation efficiency of Gd-doped samples for RhB under simulated sunlight irradiation was higher than that of pure BiFeO3 nanofibers. Among them, the degradation rate of 10BGFO nanofibers on RhB was the fastest and reached 96.3% within 30 min. After five cycles, the removal efficiency could still be maintained at about 90%. The effects of temperatures, ions, concentrations, and water quality on the removal efficiency were studied in detail, and the possible photocatalytic degradation mechanism of BGFO nanofibers was also elaborated. With the increase of Gd doping, the band gap value gradually decreased, and the specific surface area was bigger, which effectively promoted the charge separation and could inhibit the complexation of photogenerated electrons and holes and produced more active substances (·O2-, h+). This study can provide a novel, reusable, flexible photocatalyst to purify dye wastewater.

Correlated factors for Li-ion migration in ionic conductors with the fcc anion sublattice.

The development of solid-state electrolytes (SSEs) with high lithium ionic conductivities is critical for the realization of all-solid-state Li-ion batteries. Crystal structure distortions, Li polyhedron volumes, and anion charges in SSEs are reported to affect the energy landscapes, and it is paramount to investigate their correlations. Our works uncover the cooperative effect of lithium site distortions, anion charges, and lattice volumes on Li-ion migration energy barrier in superionic conductors of LiMS2 (M = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) and Li2MO3 (M = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni). Combined with the Least Absolute Shrinkage and Selection Operator analyses, the volume and Continuous symmetrical methods (CSMs) of Li tetrahedral (Tet) sites appear to have a larger effect on the manipulation of Ea for Li migration, compared to that of Li octahedral (Oct) sites, which is further confirmed by the results from the face-centered cubic (fcc) anion lattice model. For the Tet-Oct-Tet Li migration path, the CSM (the volume of Li site) has a negative (positive) correlation with Ea, while for the Oct-Tet-Oct Li migration paths, opposite correlations have been observed. The understanding of the correlation between site preference, anion charge, lattice volume, and structural distortion as well as the prediction model of Ea in terms of these three factors, namely, C-V-D model, could be useful for the design of solid-state electrolytes with lower activation energy.

Characterization of a novel AlLiMgTiZr-type light high entropy alloy

Al11Li10Mg23Ti21Zr35 was designed as a novel Light High Entropy Alloy (LHEA) considering terms and parameters of respective phase formation rules. The alloy was vacuum melted utilizing high-purity elements, then suction cast and homogenized. The experimentally measured density of the ingot was 4.43 g/cm3 compared to the theoretical density of 4.02 g/cm3. Chemical composition, microstructural properties, phase structure, compressive mechanical properties, and microhardness were characterized. Approximate chemical homogeneity was observed in the microstructure and the Hexagonal Close-Packed (HCP) solid solution phase with c/a = 1.544 and AlZr2 intermetallic compounds were identified. High specific hardness (230 Vickers. cm3/g) was achieved satisfying among all LHEAs introduced up to now. Different hardness values were measured at various points of the microstructure connected to the presence of AlZr2 intermetallic. The lattice distortion of alloys' crystal structures was analyzed accurately, and the distorted solid solution structure consists of elements with different atomic radii, proposed as the dominant mechanism (contributed more than 80%) among grain boundary, dislocation strengthening and solid solution strengthening mechanisms. The alloy's ductility was fair due to the HCP lattice and intermetallic compounds.

High-pressure evolution of the magnetic order in LaMnO3

A relationship between evolution of the long-range magnetic order, crystal structure, and lattice distortions in $\mathrm{LaMn}{\mathrm{O}}_{3}$ was studied by a combination of neutron diffraction and Raman spectroscopy at high pressures up to 39 and 50 GPa, respectively, covering the temperature range 5 to 290 K. The Raman spectra reveal a gradual structural phase transformation evolving in the pressure range of 4 to 17 GPa, caused by a modification of the Jahn-Teller (JT) lattice distortions from the static cooperative character to the local one. A presence of residual JT-distorted regions associated with the initial phase is detected up to 32 GPa, where the insulator-metal transition occurs. At higher pressure, the local JT distortions also vanish completely at further compression up to 50 GPa. In the neutron diffraction data, a strong suppression of the A-type antiferromagnetic (AFM) phase is observed over the pressure region of the phase transformation. This is accompanied by a noticeable reduction in magnitude of the ${Q}_{2}$ and ${Q}_{3}$ JT local modes. The effective ordered magnetic manganese moment is reduced about twice at pressures up to 14 GPa. At higher pressures up to 30 GPa, residual regions of the A-type AFM phase coexist with the magnetically disordered phase. In the range 30 to 39 GPa, i.e., during the pressure-induced insulator-metal transition, these regions disappear and, finally, the magnetically disordered metallic phase becomes the only ground state. The possible models of the insulator-metal transition in $\mathrm{LaMn}{\mathrm{O}}_{3}$ are analyzed.

Perovskite oxides successfully catalyze the electrolytic hydrogen production from oilfield wastewater

Although Pt/C has long been regarded as the most effective HER catalyst, the use of complicated water systems is challenged by high costs and contaminant interference. Therefore, it was shown in this paper that a low-cost perovskite oxide, SrCo0.7Fe0.3O3-δ(SCF-X, where X denotes annealing temperature), could be used in oil-field wastewater to promote electrochemical reactions for hydrogen production and that its catalytic activity can be impacted by calcination temperature. And, the outstanding catalytic activity of SCF-800 and 850 is primarily caused by crystal structure distortions and the presence of Co3+/Co4+ coupling pairs as a result of electron transfer between Co and Fe, which increases the concentration of reactive oxygen species. Furthermore, there is now more interest in SCF-850 due to its exceptional stability. In complicated systems, the current work provides a feasible route for perovskite catalysts to produce hydrogen.