Preparation and Properties of Oxygen-Selective LaGaO3-Based Ceramics with Mixed Ionic–Electronic Conduction

A continuous series of (La_0.9Sr_0.1)[(Ga_{1 – x} Fe _x )_0.8Mg_0.2]O_{3 –} perovskite solid solutions (x = 0–1) were prepared by ceramic processing techniques. X-ray diffraction, dilatometry, thermogravimetry, and dielectric spectroscopy data indicate that increasing the Fe content of the solid solutions leads to a change from oxygen ionic to ionic–electronic conduction.     

Mott–Schottky Effect in Core–Shell W@WxC Heterostructure: Boosting Both Electronic/Ionic Kinetics for Lithium Storage

The dynamics rate of traditional metal carbides (TMCs) is relatively slow, severely limiting its fast-charging capacity for lithium-ion batteries (LIBs). Herein, the core–shell W@W_xC heterostructure is developed to form Mott–Schottky heterostructure, thereby simultaneously accelerating the electronic and ionic transport kinetics during the charging/discharging process. The W nanoparticles are partially reduced into W_xC to form a particular core–shell structure with abundant heterogeneous interfaces. Benefiting from the Mott–Schottky effect, the electrons at the metal/semiconductor heterointerface can migrate spontaneously to realize an equal work function on both sides. In addition, the independent nanoparticle as well as the unique core–shell structure facilitate the ionic diffusion kinetics. As expected, the W@W_xC electrode exhibits excellent electrochemical stability for LIBs, whose capacity can be maintained at 173.8 mA h g⁻¹ after 1600 cycles at a high current density of 5 A g⁻¹. When assembled into a full cell, it can achieve an energy density of 360.2 Wh kg⁻¹. This work presents a new avenue to promote the electronic and ionic kinetics for LIBs anodes by constructing the unique Mott–Schottky heterostructure.     

Cubic NaSbS2 as an Ionic–Electronic Coupled Semiconductor for Switchable Photovoltaic and Neuromorphic Device Applications

The recent emergence of lead halide perovskites as ionic–electronic coupled semiconductors motivates the investigation of alternative solution-processable materials with similar modulatable ionic and electronic transport properties. Here, a novel semiconductor—cubic NaSbS₂—for ionic–electronic coupled transport is investigated through a combined theoretical and experimental approach. The material exhibits mixed ionic–electronic conductivity in inert atmosphere and superionic conductivity in humid air. It is shown that post deposition electronic reconfigurability in this material enabled by an electric field induces ionic segregation enabling a switchable photovoltaic effect. Utilizing post-perturbation of the ionic composition of the material via electrical biasing and persistent photoconductivity, multistate memristive synapses with higher-order weight modulations are realized for neuromorphic computing, opening up novel applications with such ionic–electronic coupled materials.     

Structural evolution of an Al–Te mixture during ball milling

An Al–Te mixture was mechanically alloyed with a planetary ball mill, and the structural evolution of the Al–Te mixture during ball milling was characterized by X-ray diffractiometry (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and thermodynamic computation. Although crystalline α-Al₂Te₃ was synthesized in the initial stage of milling, but the final product is a metastable Al₂Te_3 ? δ (Space group: Fm 3¯m) with lattice parameter a = 5.925 Å. The metastable Al₂Te_3 ? δ decomposes into Al and Te at about 140 °C.     

Electrolytic Domain Boundary between Ionic and Electronic Conduction of Doped Ceria

The electrolytic domain boundary (EDB) of doped ceria between ionic and electronic conduction is theoretically investigated with the consideration of defect association. Data from the early reports on EDB of singly, double and triply doped ceria are summarized and interpreted based on the theoretical investigation. It is proposed that samarium and gadolinium among the rare earth elements are mostly suitable for the main dopants of ceria, while further minor additions of other elements can benefit the improvement of the EDB.     

DFT + U Analysis of Structural,Electronic, and Magnetic Properties of Mn–As–Sb Ternary Systems

Electronic and magnetic investigations have been carried out on Mn–As–Sb ternary systems and their two end members, MnAs and MnSb, using ab initio techniques based on density functional theory plus U (DFT + U). Although the electronic structures of pure compounds have been extensively studied by first-principles calculations, there have been no reports of first-principles calculations of the evolution of the electronic structure with the composition. In order to get accurate results for these kinds of systems including Mn 3d electrons, we varied the U parameter from 0 to 10 eV for use in local density approximation (LDA) + U approach. The computed structural, electronic, and magnetic properties of MnX (X = As, Sb) are observed to display strong correlation with experimental data. In particular, the best agreement with the experimentis obtained within the LDA + U in which on-site Coulomb interaction parameter U _eff for Mn is taken as 3.0 eV. Next, we have studied the energetic, electronic, and magnetic properties of alloys and we have also investigated the effects of compositional disorder in both hexagonal and orthorhombic structures. Several important properties of these materials were established. The improvement achieved with the ab initio LDA + U method and the agreement with the experimental spectra are discussed.     

Sintering Metal–Organic Framework Gels for Application as Structural Adhesives

Metal–organic frameworks (MOFs)/coordination polymers are promising materials for gas separation, fuel storage, catalysis, and biopharmaceuticals. However, most applied research on MOFs is limited to these functional materials thus far. This study focuses on the potential of MOFs as structural adhesives. A sintering technique is applied to a zeolitic imidazolate framework-67 (ZIF-67) gel that enables the joining of Cu substrates, resulting in a shear strength of over 30 MPa, which is comparable to that of conventional structural adhesives. Additionally, systematic experiments are performed to evaluate the effects of temperature and pressure on adhesion, indicating that the removal of excess 2-methylimidazole and the by-product (acetic acid) from the sintered material by vaporization results in a microstructure composed of large spherical ZIF-67 crystals that are densely aggregated, which is essential for achieving a high shear strength.     

Isothermal Crystallization Kinetics of an Amorphous CuTi Alloy

Isothermal crystallization kinetics ofCu_(40)Ti_(60)amorphous alloy has been studied usingdifferential scanning calorimetry(DSC).Bothas-quenched and pre-annealed ribbons were inves-tigated.For crystallization of as-quenched amor-phous ribbon in Ar,it was found that the kineticsfollows Johnson-Mehl-Avrami equation withmean Avrami exponent n=2.58,which indicatesthat crystallization of amorphous Cu_(40)Ti_(60)is athree-dimensional diffusion controlled growth pro-cess with constant nucleation rate,i.e.,primarycrystallization process.The primary phase is thetetragonal CuTi_2.The as-quenched amorphousribbons were also crystallized in air,the results re-veal that oxidation has no significant influence oncrystallization kinetics of amorphous Cu_(40)Ti_(60).The results of crystallization of pre-annealed rib-bons show a decreasing tendency of Avrami expo-nent with increasing pre-anneal time.The localactivation energy and local Avrami exponent dur-ing crystallization process of as-quenched amor-phous alloy were also examined.     

Computer Simulation of Noncrystalline P2O5 , an Ionic–Covalent Oxide

The semiclassical molecular dynamics simulation method proposed earlier for studying ionic–covalent oxide systems was applied to noncrystalline P₂O₅. The expressions for the potentials of ionic–covalent bonds were found. The internal energy comprises the contributions from the ionization energy of phosphorus, electron affinity of oxygen, Coulombic interaction, repulsion between ionic shells, and covalent interaction. The ionic charges were computed by minimizing the potential energy at each simulation step. Taking into account mixed bonding improves agreement with the experimental data on the density, energy, and structure of condensed P₂O₅. The bond ionicity in glassy P₂O₅is about 68%. The proposed potentials are shown to be suitable for computing a number of properties of isolated P₄O₁₀molecules.     

Characterization of an Electronic Excitation on a Peierls–Hubbard Hamiltonian for a Small Cluster

We have studied the behavior of the first electronic-like excitation in a three-site Peierls–Hubbard Hamiltonian as a function of the electron-lattice coupling. This excitation corresponds to a pure electronic excitation in the absence of electron-lattice coupling. For values of electronic and phononic parameters typical of copper-oxide superconductors, this excitation is far above the first phononic excitation energies. As the electron-lattice coupling increases this first electronic-like excitation shows a decrease in energy with respect to the ground state. In contrast to the first excited state of this model, which corresponds to a polaronic excitation, the energy of this excitation does not converge to zero for strong coupling values. Based on this behavior and the projection of the corresponding state into a basis with defined charge occupation numbers, we have interpreted this result as evidence of partial charge localization within the three-site cluster. Unlike a ferroelectric state, in this model we do not observe complete charge localization even when the lattice distortion, associated with the polaronic excitation, becomes static.     

Structural properties of Cd–Co ferrites

Ferrite samples with composition, Cd $_{\emph{x}}$ Co $_{1-\emph{x}}$ Fe₂O₄ (x = 0·80, 0·85, 0·90, 0·95 and 1·0), were prepared by standard ceramic method and characterized by XRD, IR and SEM techniques. X-ray analysis confirms the formation of single phase cubic spinel structure. Lattice constant and grain size of the samples increase with increase in cadmium content. Bond length (A–O) and ionic radii ( ${\emph{r}}_{\rm {A}})$ on A-sites increase, whereas bond length (B–O) and ionic radii ( ${\emph{r}}_{\rm{B}})$ on B-site decrease. The crystallite sites of the samples lie in the range of 29·1–42·8 nm. IR study shows two absorption bands around 400 cm^???1 and 600 cm^???1 corresponding to tetrahedral and octahedral sites, respectively.     

A Metal–Organic Framework as a Multifunctional Ionic Sieve Membrane for Long-Life Aqueous Zinc–Iodide Batteries

The introduction of the redox couple of triiodide/iodide (I₃⁻/I⁻) into aqueous rechargeable zinc batteries is a promising energy-storage resource owing to its safety and cost-effectiveness. Nevertheless, the limited lifespan of zinc–iodine (Zn–I₂) batteries is currently far from satisfactory owing to the uncontrolled shuttling of triiodide and unfavorable side-reactions on the Zn anode. Herein, space-resolution Raman and micro-IR spectroscopies reveal that the Zn anode suffers from corrosion induced by both water and iodine species. Then, a metal–organic framework (MOF) is exploited as an ionic sieve membrane to simultaneously resolve these problems for Zn–I₂ batteries. The multifunctional MOF membrane, first, suppresses the shuttling of I₃⁻ and restrains related parasitic side-reaction on the Zn anode. Furthermore, by regulating the electrolyte solvation structure, the MOF channels construct a unique electrolyte structure (more aggregative ion associations than in saturated electrolyte). With the concurrent improvement on both the iodine cathode and the Zn anode, Zn–I₂ batteries achieve an ultralong lifespan (>6000 cycles), high capacity retention (84.6%), and high reversibility (Coulombic efficiency: 99.65%). This work not only systematically reveals the parasitic influence of free water and iodine species to the Zn anode, but also provides an efficient strategy to develop long-life aqueous Zn–I₂ batteries.     

Synthesis, Structural, Electrical, Magnetic Curie Temperature and Y–K Angle Studies of Mn–Cu–Ni Mixed Spinel Nanoferrites

Nanoferrites of composition Mn_0.50Cu_0.5−x Ni _x Fe₂O₄ (0.00≤x≤0.50) are prepared by chemical coprecipitation method. The prepared nano-ferrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), two probe resistivity apparatus, and vibrating sample magnetometer (VSM) to study the compositional, structural, morphological, electrical, and magnetic properties with varying concentration (x) in the composition of the prepared nanoferrites. XRD confirmed formation of single phase spinel ferrite with crystalline size in the range of 16–29 nm. The lattice parameter (a) decreases with a decrease of Cu concentration. Further information about the structure and morphology of the nanoferrites was obtained from SEM and results are in good agreement with XRD. FTIR gives information about distribution of cations and anions by confirming the presence of high and low frequency bands due to tetrahedral and octahedral sites, respectively. The electric properties were measured and analyzed by using homemade two probe resistivity apparatus showing semiconducting behavior of synthesized ferrites. The magnetic hysteresis curves clearly indicate the soft nature of the prepared samples. Various magnetic parameters such as saturation magnetization (M _s), and remanence (M _r) are calculated from the hysteresis loops and observed compositional dependent. Saturation magnetization and magnetic moment increase with Ni content. This is due to the existence of localized canted spin. Coercivity and M _s decreases while Y–K angles increase with Cu²⁺ content. The Ni²⁺ addition improves the magnetic properties. Curie temperature decreases with increase in Cu contents.     

Structural Evolution of an FeMoSiB Alloy during Ball Milling

Ball milling induced microstructure evolution in an FeMoSiB alloy with three kinds of different phase constitutions (bcc Fe solid solution and various borides) was investigated by means of X-ray diffraction and transmission electron microscopy. Experimental evidences indicate that a same final product of bcc Fe solid solution was formed upon miling for all samples. During the transformation, the XRD peaks of Fe phase shift to lower diffraction angIes; and those of borides disappear in turn, first the metastable Fe3B and Fe23B6 and then the stable Fe2B. The observed structure evolution might originate from the transformation of ordered Fe2B phase into disordered Fe solid solution.     

Influence of Ionic Liquid-Based Metal–Organic Hybrid on Thermal Degradation,Flame Retardancy,and Smoke Suppression Properties of Epoxy Resin Composites

A new multifunctional ionic liquid-based metal–organic hybrid (PMAIL) was synthesized by anion exchange between as-synthesized phosphonate-based ionic liquid and phosphomolybdic acid and applied to epoxy resin (EP) as an efficient flame retardant. As expected, with only 1 wt% addition of PMAIL, the char yield of EP-PMAIL1 composite at 700 °C was significantly improved by 108.3% from 12.0% for neat epoxy resin to 25.0%, demonstrating the outstanding catalytic charring effect of PMAIL. Meanwhile, EP-PMAIL6 composite (6 wt% addition) can reach V-0 rating in the UL-94 vertical burning tests easily, and its peak heat release rate and total smoke production of EP-PMAIL6 were dropped by 31.0 and 15.4%, respectively, compared with neat EP. Moreover, the results from cone calorimetry tests showed that the char yield of EP-PMAIL6 was enhanced by 162% from 9.5 to 24.9% compared with neat EP, resulting in a strong intumescent char layer structure with outstanding fire retardance and mechanical properties. The thermo-oxidative stable protective layer retarded the transfer of heat and flammable volatiles during combustion and protected the epoxy matrix from further degradation. In conclusion, our results might provide a new perspective for producing composites with excellent flame retardancy and smoke suppression properties using ionic liquid-based metal–organic hybrid.     

Achieving Ultralong-Cycle Zinc-Ion Battery via Synergistically Electronic and Structural Regulation of a MnO2 Nanocrystal–Carbon Hybrid Framework

Aqueous rechargeable zinc-ion batteries (ZIBs) have attracted burgeoning interests owing to the prospect in large-scale and safe energy storage application. Although manganese oxides are one of the typical cathodes of ZIBs, their practical usage is still hindered by poor service life and rate performance. Here, a MnO₂–carbon hybrid framework is reported, which is obtained in a reaction between the dimethylimidazole ligand from a rational designed MOF array and potassium permanganate, achieving ultralong-cycle-life ZIBs. The unique structural feature of uniform MnO₂ nanocrystals which are well-distributed in the carbon matrix leads to a 90.4% capacity retention after 50 000 cycles. In situ characterization and theoretical calculations verify the co-ions intercalation with boosted reaction kinetics. The hybridization between MnO₂ and carbon endows the hybrid with enhanced electrons/ions transport kinetics and robust structural stability. This work provides a facile strategy to enhance the battery performance of manganese oxide-based ZIBs.     

The Effect of Linker-to-Metal Energy Transfer on the Photooxidation Performance of an Isostructural Series of Pyrene-Based Rare-Earth Metal–Organic Frameworks

The tetratopic linker, 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H₄TBAPy) along with rare-earth (RE) ions is used for the synthesis of 9 isostructures of a metal–organic framework (MOF) with shp topology, named RE-CU-10 (RE = Y(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), and Lu(III)). The synthesis of each RE-CU-10 analogue requires different reaction conditions to achieve phase pure products. Single crystal X-ray diffraction indicates the presence of a RE₉-cluster in Y- to Tm-CU-10, while a RE₁₁-cluster is observed for Yb- and Lu-CU-10. The photooxidation performance of RE-CU-10 analogues is evaluated, observing competition between linker-to-metal energy transfer versus the generation of singlet oxygen. The singlet oxygen produced is used to detoxify a mustard gas simulant 2-chloroethylethyl sulfide, with half-lives ranging from 4.0 to 5.8 min, some of the fastest reported to date using UV-irradiation and < 1 mol% catalyst, in methanol under O₂ saturation.     

General Decomposition Pathway of Organic–Inorganic Hybrid Perovskites through an Intermediate Superstructure and its Suppression Mechanism

Organic–inorganic hybrid perovskites (OIHPs) have generated considerable excitement due to their promising photovoltaic performance. However, the commercialization of perovskite solar cells (PSCs) is still plagued by the structural degradation of the OIHPs. Here, the decomposition mechanism of OIHPs under electron beam irradiation is investigated via transmission electron microscopy, and a general decomposition pathway for both tetragonal CH₃NH₃PbI₃ and cubic CH₃NH₃PbBr₃ is uncovered through an intermediate superstructure state of CH₃NH₃PbX_2.5, X = I, Br, with ordered vacancies into final lead halides. Such decomposition can be suppressed via carbon coating by stabilization of the perovskite structure framework. These findings reveal the general degradation pathway of OIHPs and suggest an effective strategy to suppress it, and the atomistic insight learnt may be useful for improving the stability of PSCs.     

Degradation Kinetics of Organic–Inorganic Hybrid Materials from Micro-Raman Spectroscopy and Density-Functional Theory: The Case of β-ZnTe(en)0.5

Organic–inorganic hybrid materials often face a stability challenge. β-ZnTe(en)_0.5, which uniquely has over 15-year real-time degradation data, is taken as a prototype structure to demonstrate an accelerated thermal aging method for assessing the intrinsic and ambient-condition long-term stability of hybrid materials. Micro-Raman spectroscopy is used to investigate the thermal degradation of β-ZnTe(en)_0.5 in a protected condition and in air by monitoring the temperature dependences of the intrinsic and degradation-product Raman modes. First, to understand the intrinsic degradation mechanism, the transition state of the degradation is identified, then using a density functional theory, the intrinsic energy barrier between the transition state and ground state is calculated to be 1.70 eV, in excellent agreement with the measured thermal degradation barrier of 1.62 eV in N₂ environment. Second, for the ambient-condition degradation, a reduced thermal activation barrier of 0.92 eV is obtained due to oxidation, corresponding to a projected ambient half-life of 40 years at room temperature, in general agreement with the experimental observation of no apparent degradation over 15 years. Furthermore, the study reveals a mechanism, conformation distortion enhanced stability, which plays a pivotal role in forming the high kinetic barrier, contributing greatly to the impressive long-term stability of β-ZnTe(en)_0.5.