Multicomponent Oxide Research Articles

Time-resolved luminescence of YAG:Ce and YAGG:Ce ceramics prepared by electron beam assisted synthesis

The luminescence characteristics of YAG:Ce and YAGG:Ce ceramic phosphors produced by electron beam assisted synthesis have been investigated. The obtained emission and decay kinetics characteristics have been compared with those for commercial phosphors synthesized by conventional methods and showed good qualitative and quantitative correspondence. In our opinion, the used electron-beam-assisted synthesis method could be considered as a perspective production method of high refractory multicomponent oxide ceramics.

Oxygen Pressure Influence on Properties of Nanocrystalline LiNbO3 Films Grown by Laser Ablation.

Energy conversion devices draw much attention due to their effective usage of energy and resulting decrease in CO2 emissions, which slows down the global warming processes. Fabrication of energy conversion devices based on ferroelectric and piezoelectric lead-free films is complicated due to the difficulties associated with insufficient elaboration of growth methods. Most ferroelectric and piezoelectric materials (LiNbO3, BaTiO3, etc.) are multi-component oxides, which significantly complicates their integration with micro- and nanoelectronic technology. This paper reports the effect of the oxygen pressure on the properties of nanocrystalline lithium niobate (LiNbO3) films grown by pulsed laser deposition on SiO2/Si structures. We theoretically investigated the mechanisms of LiNbO3 dissociation at various oxygen pressures. The results of x-ray photoelectron spectroscopy study have shown that conditions for the formation of LiNbO3 films are created only at an oxygen pressure of 1 × 10−2 Torr. At low residual pressure (1 × 10−5 Torr), a lack of oxygen in the formed films leads to the formation of niobium oxide (Nb2O5) clusters. The presented theoretical and experimental results provide an enhanced understanding of the nanocrystalline LiNbO3 films growth with target parameters using pulsed laser deposition for the implementation of piezoelectric and photoelectric energy converters.

On the elastic anisotropy of the entropy-stabilized oxide (Mg, Co, Ni, Cu, Zn)O compound

In this paper, we study the elastic properties of the entropy-stabilized oxide (Mg, Co, Ni, Cu, Zn)O using experimental and first principles techniques. Our measurements of the indentation modulus on grains with a wide range of crystallographic orientations of the entropy-stabilized oxide revealed a high degree of elastic isotropy at ambient conditions. First principles calculations predict mild elastic anisotropy for the paramagnetic structure, which decreases when the system is considered to be non-magnetic. When the antiferromagnetic state of CoO, CuO, and NiO is accounted for in the calculations, a slight increase in elastic anisotropy is observed, suggesting a coupling between magnetic ordering and the orientation dependent elastic properties. Furthermore, an examination of the local structure reveals that the isotropy is favored through local ionic distortions of Cu and Zn—due to their tendencies to form tenorite and wurtzite phases. The relationships between the elastic properties of the multicomponent oxide and those of its constituent binary oxides are reviewed. These insights open up new avenues for controlling isotropy for technological applications through tuning composition and structure in the entropy-stabilized oxide or the high-entropy compounds in general.

Review of current high-ZT thermoelectric materials

Thermoelectric materials are capable of converting heat and electricity to each other. Thermoelectric devices can be miniaturized and highly integrated with existing semiconductor chip systems with microgenerators or microrefrigerators. After years of research and accumulation, BiTe series, SnSe series, CuSe series, half-Heusler series, multicomponent oxides series, organic–inorganic composites series, and GeTe/PbTe series have been found to have excellent thermoelectric properties. According to theoretical calculation, when the diameter of Bi2Te3 nanowires is 5 A, the ZT value reaches 14, and graphdiyne has a ZT value of 4.8 at 300 K. Experimental measurements revealed that the ZT value of n-type SnSe reached 2.8. This review would focus on the updated experimental and theoretical achievements of seven kinds of materials, including BiTe series, SnSe series, CuSe series, multicomponent oxides, half-Heusler alloys, organic–inorganic composites, and GeTe/PbTe series. The preparation method, microstructure characteristics, device structure, and thermoelectric properties of each material will be described in detail. By analyzing the performance of these materials, three possible development directions are put forward for how to further improve the thermoelectric properties of materials.

Sensitization mechanism of Bi/Nd co-doped germanosilicate glass for infrared applications

The sensitization effect of co-doping luminescent center ions with energy donors to enhance luminous efficiency and increase the coefficient has been widely considered in various aspects, particularly in the area of near-infrared optical communication. In this study, it is claimed for the first time that both the Bi0/Bi1+ centers and Bi3+ active ions can efficiently absorb pumping energy and improve the luminescence of Nd3+ ions for green and NIR emissions, respectively. In addition, the Judd–Ofelt (J–O) intensity parameters and the radiation characteristics of Nd3+ ions within the NIR region are also discussed based on the J–O theory. Hence, Bi/Nd coped multicomponent oxide glasses have an application potential within the NIR biological communication window.

Multicomponent metal oxides derived from Mn-BTC anchoring with metal acetylacetonate complexes as excellent catalysts for VOCs and CO oxidation

It is well-known that single-phase metal oxides can be prepared by using metal-organic frameworks (MOFs) as sacrificial templates. In this contribution, we report a facile and scalable route for the preparation of multicomponent metal oxide nanomaterials (MMONs) with high dispersion and tailorable chemical compositions. Specifically, a series of MMONs have been prepared from the calcination of Mn-BTC nanorods together with various transition-metal acetylacetonate complexes (M(acac)2), wherein M(acac)2 was chemically anchored to the porous Mn-BTC with molecular-level dispersion during the one-pot synthesis. The large acac ligands benefit the uniform dispersion of the hetero-metals in the composites during the calcination in air. As a proof of concept application, we have demonstrated that the as-derived MMONs exhibited remarkable catalytic activities in the thermal oxidation of benzene and CO, respectively, which were superior to the traditional mixed metal oxides prepared from the coprecipitation method. The apparent activation energy was calculated and the surface chemical compositions of MMONs were characterized to assess the catalytic roles. In addition, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was also used to reveal the catalytic mechanisms and the synergistic effects of the obtained MMONs.

Highly Conductive Sb-SnO2 Nanocrystals Synthesized by Dual Nonthermal Plasmas.

Nonthermal plasma synthesis of transparent conducting oxide nanocrystals can offer advantages, for example, ligand-free surfaces, over traditionally used colloidal synthesis methods. When it comes to multicomponent (doped) metal oxide nanocrystal synthesis, uniform distribution of different metal elements and suppressing surface segregation of secondary resistive phases have been concerns. Specifically, surface segregation of resistive secondary phases reduces the electrical conductivity of nanocrystal assemblies. In this work, we demonstrate a nonthermal dual-plasma synthesis method capable of forming Sb-SnO2 (ATO) nanocrystals with a uniform composition distribution and apparently insignificant surface segregation of the dopant. A drastic increase in conductivity was observed in ATO thin films comprised of nanocrystals formed using a dual-plasma configuration compared to nanocrystals formed using a single-plasma configuration. The conductivity values of as-deposited porous films comprised of ATO nanocrystals, prepared using the dual-plasma approach, were on the order of 0.1 S cm-1, which to our knowledge is the highest conductivity reported to-date for that type of high surface area material. Annealing the films comprised of ATO nanocrystals at 500 °C for 2 h in air increased the conductivity and improved ambient stability, without significantly affecting the crystallite size.

A Study of Nickel and Iron Reduction Silicothermic Process by Thermodynamic Simulation

The results of studying the effect of silicon concentration of ferrosilicon: FeSi5 (5% Si), FeSi20 (20% Si), FeSi35 (35% Si), FeSi50 (50% Si), FeSi65 (65% Si) on the degree of nickel (ηNi) and iron (ηFe) reduction of the CaO-SiO2-MgO-Al2O3-FeO-NiO-P2O5 multicomponent oxide system at a temperature of 1500 °C by thermodynamic simulation are given2. The HSC Chemistry 6.12 software package developed by Outokumpu (Finland) was used for the simulation. The chemical compounds Ni3Si and Ni5Si2 with the corresponding thermodynamic characteristics are entered into the database. The calculations were performed by the “Equilibrium Compositions” subroutine at a gas pressure of 1 atm, containing 2.24 m3 N2, as a neutral additive. The obtained modeling results indicate the thermodynamic possibility of nickel and iron reduction from the CaO-SiO2-MgO-Al2O3-FeO-NiO-P2O5 oxide system by silicon of ferrosilicon. The degree of iron reduction increases from 88.8 to 91.4%, with an increase in the silicon concentration of ferrosilicon [Si]FeSi from 5 to 65%. The degree of nickel reduction with an increase in the silicon concentration of ferrosilicon remains almost unchanged and amounts to 99.8-99.7%. The degree of use of silicon is 92.1–94.5%. The chemical composition of the complex alloy – ferrosiliconickel is determined. The obtained simulation results can be used to develop the technology for producing ferrosiliconickel from nickel ore by silicothermic method.

Assessment of MgHf4P6O24 Electroceramic Oxide Electrolyte in High-Temperature Electrochemical Sensor for Sensing Mg in Non-Ferrous Alloys

The chemical synthesis of MgHf4P6O24 multicomponent nanostructured ceramic oxide electrolyte was achieved using a modified sol-gel chemical process by substituting the tetravalent Zr4+ B-site in MgZr4P6O24 solid-state electrolyte [1, 2] with tetravalent Hf4+ ceramic oxide resulting in a considerably low activation energy (Ea = 0.74 ± 0.04 eV), promising ionic conductivity (4.52 x 10-4 Scm-1 at 747oC), electroceramic MgHf4P6O24 solid-state electrolyte.MgHf4P6O24 solid-state electroceramic oxide electrolyte was calcined at a relatively low temperature range of 800-900oC, the calcined nanopowders were pressed into pellets of 13mm diameter (Ø) and 3.8mm thickness with a uniaxial steel die at 5kN compressive pressure and sintered at 1000 ≤ T/oC ≤ 1550 temperature range. However, 1300oC was adopted as the sintering temperature in this study haven achieved optimum density and stable sample composition at that temperature. X-ray diffraction reveals a good crystallinity of the electroceramic oxide with an average crystallite size of 20±2 nm and 42±2 nm at 800oC and 900oC, respectively, indicating that crystallite size increases as a function of calcination temperature, which is very consistent with the simultaneous TGA-DSC thermal analysis profiles and confirmed using HR-TEM. The refined crystallographic data and ionic conductivity properties of the novel MgHf4P6O24 ceramic oxide solid-state electrolyte was reported for the first time in this study. SEM-EDS characterisation technique was used for determining both structural and compositional homogeneity. The sintered MgHf4P6O24 electroceramic oxide electrolyte was characterised for their electrical and thermodynamic properties thereby identifying reliable ionic and transport properties of the electroceramic oxide; The average transport number for Mg2+-cations in MgHf4P6O24 electroceramic oxide electrolyte measured as a function of Mg concentration in molten Al is 0.84±0.03. The ionic conductivity and thermodynamic analysis of the novel solid-state electroceramic oxide electrolyte in this study was compared with those of MgZr4P6O24 electrolyte [3], showing novel improvement in the trend of the ionic conductivity and thermodynamic properties of both electroceramic oxide electrolytes.Relying on the structural, chemical stability and ionic conductivity data characterised in this study, solid-state electrochemical Mg-sensor was designed and fabricated, then testing of the high-temperature Mg-sensor in molten Al alloys by the electrochemical method was achieved as shown in Figure 1 [3]. The novel high-temperature solid-state Mg-sensor was fabricated using the novel high conducting Mg2+-cation solid-state electroceramic oxide electrolyte characterised in this study by incorporating a biphasic powder mixture of MgCr2O4+Cr2O3 solid-state ceramic reference electrode in air, showing promising trend after successfully sensing Mg dissolved in molten Al alloys at 700±5oC. A linear dependence of sensor voltage on the logarithm of Mg concentration was obtained. The thermodynamic activity of Mg in molten Al alloy shows a rather negative deviation from Raoult's law. Solid-state MgHf4P6O24 electroceramic oxide electrolyte has useful potential applications in solid-state Mg-sensors during refining, virgin metals alloying and scrap metal recycling for the benefit of our environment and depleting climate.

Controlled Introduction of Defects to Delafossite Metals by Electron Irradiation

The delafossite metals PdCoO$_{2}$, PtCoO$_{2}$ and PdCrO$_{2}$ are among the highest conductivity materials known, with low temperature mean free paths of tens of microns in the best as-grown single crystals. A key question is whether these very low resistive scattering rates result from strongly suppressed backscattering due to special features of the electronic structure, or are a consequence of highly unusual levels of crystalline perfection. We report the results of experiments in which high energy electron irradiation was used to introduce point disorder to the Pd and Pt layers in which the conduction occurs. We obtain the cross-section for formation of Frenkel pairs in absolute units, and cross-check our analysis with first principles calculations of the relevant atomic displacement energies. We observe an increase of resistivity that is linear in defect density with a slope consistent with scattering in the unitary limit. Our results enable us to deduce that the as-grown crystals contain extremely low levels of in-plane defects of approximately $0.001\%$. This confirms that crystalline perfection is the most important factor in realizing the long mean free paths, and highlights how unusual these delafossite metals are in comparison with the vast majority of other multi-component oxides and alloys. We discuss the implications of our findings for future materials research.

Crystallization data-driven proposal on distribution model of composition fluctuations in structure of oxide glasses

Understanding of nanoscale heterogeneous structure, in particular composition fluctuations in multi-component oxide glasses, is a great challenge in the science and technology of solid state materials. The data on the crystallization of oxide glasses, especially the relationship between crystalline phases and glass compositions, are reviewed, and the distribution model of composition fluctuations is proposed for the first time. The crystallization data-driven proposal model on composition fluctuations consists of network former-rich (high viscosity) strong region and network modifier-rich (low viscosity) fragile region, and crystallization including the formation of metastable phases is initiated preferentially in the fragile region. Crystallization behaviors such as lithium disilicate Li2Si2O5 crystals in Li2O-2SiO2 glass, LiNbO3 crystals in 40Li2O-32Nb2O5-28SiO2 glass, and ferroelastic β′-Gd2(MoO4)3 crystals in 21.25Gd2O3-63.75MoO3-15B2O3 glass are reviewed as model cases. The proposed model will shed new light on the medium-range order and nanoscale heterogeneous structure in oxide glasses and also will guide to an innovative design of glass compositions leading to new functional glasses and glass-ceramics.

Dissolution kinetics of arbitrarily-shaped alumina in oxide melt: An integration of phase-field modelling and real-time observation study

Abstract A feasibility study of utilizing a phase-field model considering the convection effect is performed in this work to investigate the dissolution kinetics of arbitrarily-shaped alumina particle in the oxide melt. The established model has been benchmarked by high temperature confocal laser scanning microscope (HT-CLSM) to observe the polycrystalline sapphire dissolution in multicomponent oxide melt. The effects of alumina morphology and temperature on the dissolution kinetics were studied quantitatively. It is for the first time found that the dissolution of irregular alumina particle in oxide melt shows a double-fold smooth anisotropy behavior. The dissolution rate of alumina particle is governed by the interface interactions rather than the self-diffusion of dissolved component in oxide melt. Increasing the temperature, the interfacial mobility coefficient increases, and the effect of alumina particle shape on the dissolution rate decreases. The temperature variation has a minor influence on the shape evolution of alumina during dissolution process. The convection intensity affects both the dissolution rate and shape evolution of alumina particle. An increased convection intensity increases the dissolution rate. As the convection partially affects the contact area of alumina particle with oxide melt, a decreased alumina particle curvature increases the dissolution rate. When the convection affects the whole contact area of alumina particle with oxide melt, the contact area plays an important role on the dissolution rate. The obtained methodology can be applied to investigate a general dissolution phenomenon in the high temperature oxide melt in materials science.

Carbon-templated strategy toward the synthesis of dense and yolk-shell multi-component transition metal oxide cathode microspheres for high-performance Li ion batteries

Development of efficient strategies for the synthesis of multicomponent microspheres applicable to cathodes in lithium ion batteries is in urgent need. This paper presents ‘drop and dry’ method for synthesizing dense and yolk-shell multicomponent transition metal oxide microspheres. The infiltration of ethanol solution containing several metal precursors into highly porous carbon template microspheres through repetitive drop and dry process and subsequent heat treatment under oxygen atmosphere result in dense and yolk-shell microspheres. The first target cathode material is LiMn1.5Ni0.5O4, which operates at high voltage. After infiltration of Li, Mn, and Ni salts into the pores of the carbonaceous microspheres, stepwise heat treatment under low oxygen flow rate yields dense LiMn1.5Ni0.5O4 microspheres exhibiting non-aggregation characteristics and narrow size distribution. In comparison, one-step oxidation of carbon microspheres containing metal salts under high oxygen flow rate results in yolk-shell LiMn1.5Ni0.5O4 microspheres. The dense and yolk-shell microspheres exhibit stable cycle performance and capacities of 113 and 111 mA h g−1 are delivered after 1200 cycles at 10 C rate, respectively. In addition, discharge capacities of 69 and 44 mA h g−1 for yolk-shell and dense microspheres, respectively, are delivered at a high current density of 50 C.

The emergent field of high entropy oxides: Design, prospects, challenges, and opportunities for tailoring material properties

A new class of ceramics, called entropy stabilized oxides, High Entropy Oxides (HEOs), multicomponent oxides, compositionally complex oxides, or polycation oxides, has generated considerable research interest since the first report in 2015. This multicomponent approach has created new opportunities for materials design and discovery. This Perspective will highlight some current research developments and possible applications while also providing an overview of the many successfully synthesized HEO systems to date. The polycation approach to composition development will be discussed along with a few case studies, challenges, and future possibilities afforded by this novel class of materials.

Facile Synthesis of Novel Parallelogram-Like NH4CoPO4 · H2O/Ni3(PO4)2 · 8H2O/MnO2 Composites for High-Performance Supercapacitors

Abstract To construct novel multicomponent transition metal oxides with the synergistic effect is always the most important strategy to improve the electrochemical performance of supercapacitor electrode materials. Here, a new type of parallelogram-like NH4CoPO4 · H2O/Ni3(PO4)2 · 8H2O/MnO2 (NNM) composites were successfully prepared by a simple hydrothermal method, and the addition amount of MnO2 was adjusted in detail. The morphology, structure, composition, particle size, and distribution of the electrode were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectrum, and laser particle size analyzer. The results showed that when MnO2 was added at 9.7 wt%, the resulting NNM-9.7 composite exhibited a parallelogram-like morphology with an average length, width. and thickness of 5, 3, and 0.2 µm, respectively. The results of cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) show that the NNM-9.7 electrode has large specific surface area, good conductivity, and abundant porosity, which makes it to have high-specific capacity (1180 F g−1, 1 A g−1) and excellent rate retention (980 F g−1, 10 A g−1) when compared with other electrodes, which is better than most reported electrodes of nickel–cobalt oxides/hydroxides. These results indicate that the novel NNM-9.7 composite with parallelogram-like shape and its synthesis method may provide a feasible solution for supercapacitors' material issues.

Synthesis and phase stability of zirconia-lanthania-ytterbia-yttria nanoparticles; a promising advanced TBC material

ABSTRACT Advanced thermal barrier coatings (TBCs) developed by incorporating multicomponent rare earth oxide dopants into zirconia are promising alternative to replace yttria-stabilized zirconia (YSZ) thermal barrier coatings. In this study, a zirconia-based nanopowder coating doped by multiple rare earth oxides (YLaYbZr: 5.86 Mol.%Y2O3-1.99 Mol.%La2O3-1.98 Mol.%Yb2O3-ZrO2) was synthesized using co-precipitation technique which is advantageous in terms of simplicity and cost-effectiveness. The product was then characterized using X-ray diffraction (XRD) method and field emission scanning electron microscopy (FESEM). The stability of YLaYbZr compound was studied after a heat treating the product at 1300°C for 50 h. The results indicated that the initially obtained powder was a metastable tetragonal (t-prime) zirconia. Rietveld refinement of the XRD data from YLaYbZr powder after 50 h of heat treatment at 1300°C confirmed stabilization of zirconia in the t-prime phase with around 15 wt.% monoclinic impurity. Furthermore, FESEM results (before and after heat treatment) indicated orderly particles of uniform shape and size with a small tendency toward agglomeration.

Functional Multicomponent Metal Oxide Films Based on Sr, Sn, Fe, and Mo in the Anodic Alumina Matrices

Functional Multicomponent Metal Oxide Films Based on Sr, Sn, Fe, and Mo in the Anodic Alumina Matrices

Cu-Mg-Fe-O-(Ce) Complex Oxides as Catalysts of Selective Catalytic Oxidation of Ammonia to Dinitrogen (NH3-SCO)

Multicomponent oxide systems 800-Cu-Mg-Fe-O and 800-Cu-Mg-Fe-O-Ce were tested as catalysts of selective catalytic oxidation of ammonia to dinitrogen (NH3-SCO) process. Materials were obtained by calcination of hydrotalcite-like compounds at temperature 800 °C. Some catalysts were doped with cerium by the wet impregnation method. Not only simple oxides, but also complex spinel-like phases were formed during calcination. The influence of chemical composition, especially the occurrence of spinel phases, copper loading and impregnation by cerium, were investigated. Materials were characterized by several techniques: X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), low-temperature nitrogen adsorption (BET), cyclic voltammetry (CV), temperature programmed reduction (H2-TPR), UV-vis diffuse reflectance spectroscopy and scanning electron microscopy (SEM). Examined oxides were found to be active as catalysts of selective catalytic oxidation of ammonia with high selectivity to N2 at temperatures above 300 °C. Catalysts with low copper amounts (up to 12 wt %) impregnated by Ce were slightly more active at lower temperatures (up to 350 °C) than non-impregnated samples. However, when an optimal amount of copper (12 wt %) was used, the presence of cerium did not affect catalytic properties. Copper overloading caused a rearrangement of present phases accompanied by the steep changes in reducibility, specific surface area, direct band gap, crystallinity, dispersion of CuO active phase and Cu2+ accessibility leading to the decrease in catalytic activity.

Transient shrinkage behavior of wustite-centered binary/ternary/quaternary/quinary-component oxide packed beds in a reducing atmosphere up to 1773 K

Wustite (FeO)-centered multicomponent oxides play an important role in the ironmaking process, and a complete understanding of their high temperature behaviors is of great importance for process optimization to achieve high efficiency and low emissions during industrial production. In this work, the transient shrinkages of FeO-centered multicomponent oxide packed beds are quantitatively determined in a reducing atmosphere up to 1773 K, and the effects of the interactions between the oxides on the shrinkage rate (SR) are qualitatively evaluated. The results show that although mixing CaO with FeO increases the SR to 0.42%/K below 1173 K, further mixing with SiO2 or Al2O3 significantly limits this enhancement effect due to the formation of an olivine or spinel phase. However, in the subsequent stage, the SR increases to as high as 0.44%/K after CO is injected. The interaction between FeO and MgO leads to an SR of greater than 0.20%/K at lower temperatures, but it causes a decrease in the SR from 0.33%/K to 0.16%/K between 1173 K and 1273 K. Meanwhile, adding SiO2 slows the reduction reaction, and the SR correspondingly decreases further to 0.04%/K. On the other hand, the interaction between CaO and Al2O3 takes precedence over the interaction between SiO2 and MgO and dominates the shrinkage process in the quinary-component case, and the preferentially formed CaAl2O4 spinel phase hinders the formation of the Mg2SiO4 olivine phase.

Nonstoichiometric Cu0.6Ni0.4Co2O4 Nanowires as an Anode Material for High Performance Lithium Storage.

Transition metal oxide is one of the most promising anode materials for lithium-ion batteries. Generally, the electrochemical property of transition metal oxides can be improved by optimizing their element components and controlling their nano-architecture. Herein, we designed nonstoichiometric Cu0.6Ni0.4Co2O4 nanowires for high performance lithium-ion storage. It is found that the specific capacity of Cu0.6Ni0.4Co2O4 nanowires remain 880 mAh g−1 after 50 cycles, exhibiting much better electrochemical performance than CuCo2O4 and NiCo2O4. After experiencing a large current charge and discharge state, the discharge capacity of Cu0.6Ni0.4Co2O4 nanowires recovers to 780 mAh g−1 at 50 mA g−1, which is ca. 88% of the initial capacity. The high electrochemical performance of Cu0.6Ni0.4Co2O4 nanowires is related to their better electronic conductivity and synergistic effect of metals. This work may provide a new strategy for the design of multicomponent transition metal oxides as anode materials for lithium-ion batteries.