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A promising approach to the next generation of low-power, functional, and green nanoelectronics relies on advances in the electric-field control of lattice, charge, orbital, and spin degrees of freedom in novel materials. The possibility of electric-field control of these multiple materials functionalities offers interesting options across a range of modern technologies, including information communication, computing processes, data storage, active components, and functional electronics. This article reviews electric-field control and modulation of various degrees of freedom through the medium of multiferroic BiFeO3. Coexisting order parameters and inherent couplings in this materials system form a potent playground, enabling direct and indirect manipulation to obtain intriguing properties and functionalities with an electric stimulus. An in-depth understanding of those electrically controlled phenomena and breakthroughs is highlighted, paving a new route toward multifunctional nanoelectronics. This article concludes with a brief discussion on foreseeable challenges as well as future directions.

Powders of barium strontium titanate Ba0.4Sr0.6TiO3 with the particle size smaller than 300 nm were prepared by reactions in inorganic salt melts. The reaction was performed in a melt of a low-melting salt, KNO3. The frequency and capacitance–voltage characteristics of the synthesized powders were studied. The paraelectric state of barium strontium titanate of the examined composition is consistent with published data. The method developed, compared to solid-phase sintering, allows synthesis of complex oxide compounds at considerably lower temperatures and in shorter time.

【A precipitation behavior of nano-oxide particle in Fe- $5Y_2O_3$ alloy powders is studied. The mechanically alloyed Fe- $5Y_2O_3$ powders are pressed at $750^{\circ}C$ for 1h, $850^{\circ}C$ for 1h and $1150^{\circ}C$ for 1h, respectively. The results of Xray diffraction pattern analysis indicate that the $Y_2O_3$ diffraction peak disappear after mechanically alloying process, but $Y_2O_3$ and $YFe_2O_4$ complex oxide precipitates peak are observed in the powders pressed at $1150^{\circ}C$ . The differential scanning calorimetry study results reveal that the formation of precipitates occur at around $1054^{\circ}C$ . Based on the transmission electron microscopy analysis result, the oxide particles with a composition of Y-Fe-O are found in the Fe- $5Y_2O_3$ alloy powders pressed at 1150oC. It is thus conclude that the mechanically alloyed Fe- $5Y_2O_3$ powders have no precipitates and the oxide particles in the powders are formed by a high temperature heat-treatment.】

The discovery of two-dimensional electron gases (2DEGs) in SrTiO3-based heterostructures provides new opportunities for nanoelectronics. Herein, we create a new type of oxide 2DEG by the epitaxial-strain-induced polarization at an otherwise nonpolar perovskite-type interface of CaZrO3/SrTiO3. Remarkably, this heterointerface is atomically sharp, and exhibits a high electron mobility exceeding 60,000 cm2V-1s-1 at low temperatures. The 2DEG carrier density exhibits a critical dependence on the film thickness, in good agreement with the polarization induced 2DEG scheme., 19 pages, 4 figs; Nano Letters,2015, published online

Experimental results concerning the formation of nanostructured powders of complex oxides using the technology of a continuous solid-phase synthesis are discussed. It is shown that the synthesized powders are a set of nanostructured macroobjects whose formation obeys uniform regularities despite substantial differences in solid-phase reactions for individual oxide materials. The peculiarities of controlling the morphology of nanostructured macroobjects and granulometric composition of the synthesized powders are considered. It has been shown that the predominant influence on the optimization of sizes of formed nanostructured macroobjects is the temperature of synthesis, while the synthesis duration affects the optimal relation between them. In this case, the formation of the granulometric composition of the synthesized oxide material proceeds directly in the course of synthesis by the continuous self-optimization of the system as a whole. It has been shown that the use of continuous solid-phase technology allows us to synthesize strontium aluminate and lithium iron phosphate directly in an air medium.

Uniform Mn–Co mixed oxide solid, hollow and yolk–shell nanospheres with nanometer-sized building blocks have been successfully fabricated by heat-treatment of their Mn–Co alkoxyacetate precursors at a proper ramping rate. The formation of the hollow and yolk–shell structures during the thermal decomposition is mainly based on the heterogeneous contraction caused by non-equilibrium heat treatment. In virtue of the unique structural features, the resultant Mn–Co oxide nanospheres with different interiors were used as catalysts in CH4 combustion, and showed an excellent catalytic activity. Catalytic results suggest that the (Co,Mn)(Co,Mn)2O4 yolk–shell nanospheres show relatively higher activity.

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TEAM1 has taken place in Sete (France) on 4, 5, 6 july 2017. It has gathered a little less than 40 participants who presented communications on various fields of advanced materials, and on experimental facilities or experimental methods, that are briefly summarized in the present volume. Presented abstracts deal with fullerenes, graphene, thin films, oxides, ferroelectrics, pyroelectrics, piezoelectrics, superconductors, nanomaterials, photovoltaics, X-ray diffraction, electron diffraction, electron microscopy, electron holography, carbon nanotubes, nanorods, ZnO.

The band alignment at an Al2O3/SrTiO3 heterointerface forming a two-dimensional electron gas (2DEG) was investigated using scanning photocurrent microscopy (SPCM) in an electrolyte-gated environment. We used a focused UV laser source for above-the-bandgap illumination on the SrTiO3 layer, creating electron-hole pairs that contributed to the photocurrent through migration towards the metal electrodes. The polarity of the SPCM signals of a bare SrTiO3 device shows typical p-type behavior at zero gate bias, in which the photogenerated electrons are collected by the electrodes. In contrast, the SPCM polarity of 2DEG device indicates that the hole carriers were collected by the metal electrodes. Careful transport measurements revealed that the gate-dependent conductance of the 2DEG devices exhibits n-type switching behavior. More importantly, the SPCM signals in 2DEG devices demonstrated very unique gate-responses that cannot be found in conventional semiconducting devices, based on which we were able to perform detailed investigation into the electronic band alignment of the 2DEG devices and obtain the valence band offset at the heterointerface.

Electron mobility is one of the most-debated key attributes of low-dimensional electron systems emerging at complex oxide heterointerfaces. However, a common understanding of how electron mobility can be optimized in these systems has not been achieved so far. Here, we discuss a novel approach for achieving a systematic increase in electron mobility in polar/nonpolar perovskite interfaces by suppressing the thermodynamically required defect formation at the nanoscale. We discuss the transport properties of electron gases established at interfaces between SrTiO3 and various polar perovskites [LaAlO3, NdGaO3, and (La,Sr)(Al,Ta)O3], allowing for the individual variation of epitaxial strain and charge transfer among these epitaxial interfaces. As we show, the reduced charge transfer at (La,Sr)(Al,Ta)O3/SrTiO3 interfaces yields a systematic increase in electron mobility, while the reduced epitaxial strain has only minor impact. As thermodynamic continuum simulations suggest, the charge transfer across these in...

Complex oxide materials in the form of polycrystalline solids, such as SrTiO3, LaMnO3, La1−xSrxMnO3 are usually synthesized by the solid state synthesis method. It is the most commonly used method to prepare polycrystalline crystals from a mixture of solid starting materials by heating at high temperatures (1000–1500 ℃).

Focusing on improving the galvanizability of the third generation automotive steel, the effect of surface oxide morphologies on the galvanizability was studied. The results show that the surface oxide types of sample steels by X-ray photoelectron spectroscopy (XPS) analysis after annealing in different conditions are the same. Only MnO, MnO2 and Cr2O3 were detected and no complex oxide exists on the surface. Morphologies of surface oxides can greatly influence the galvanizability of the third generation automotive steel. Nodule-like oxide surface can contribute to better wettability and inhibition layer than vitreous film-like oxide surface. Galvanized panels of nodule-like oxide surface steels only show pinhole-sized bare spots, while panels galvanized from vitreous film-like oxide surface steels reveal larger areas of bare spots and uncoated areas. Inhibition layer observed in galvanized panels of nodule-like oxide surface steels is compact but not homogeneous; some inhibition layer grains are fine, and others are coarse, while the inhibition layer grains of panels galvanized from vitreous film-like oxide surface steels have a non-compact morphology with some particularly fine equiaxed crystals which developed deficiently.

The catalytic activity of manganese ferrite MnFe2O4 and the oxides MnO and Fe2O3 in the steam reforming of ethanol (SRE) has been studied. The similarity of the catalytic activity of Fe2O3 and MnFe2O4 has been established which may indicate the predominant role of the iron ions in the formation of the catalytic activity of manganese ferrite. The complex oxide MnFe2O4 exceeds the simple oxides in selectivity to the desired product of SRE – hydrogen.

Atom probe tomography (APT) is a powerful materials characterization technique capable of ppm chemical resolution and near atomic scale spatial resolution. However, owing to a number of factors, the technique has not been widely applied to insulating materials and even less to complex oxides. In this study, we outline the methodology necessary to obtain high-quality results on a technologically relevant complex oxide Pb(Zr,Ti)O3 (or PZT) using laser-assisted APT on both bulk and thin film specimens. We show how, with optimized and well-controlled conditions, APT complements conventional techniques such as STEM-EDS. The correlative information can be used to obtain the nanoscale 3-D chemical information and investigate the nanoscale distribution of cations. Using nearest-neighbor cluster analysis routines, 5–10 nm segregation of B-site cations was detected in bulk sintered PZT 53/47 from chemically prepared powders. No statistically significant segregation of B-site cations was observed in thin film specimens. This work opens new avenues toward understanding the process-structure properties in complex materials at length scales heretofore unachievable.

Two-dimensional electron gases (2DEGs) at oxide interfaces may exhibit unique properties, including effects from strong electron correlations, extremely high electron densities, magnetism, and 2D superconductivity. This article discusses routes to high-mobility 2DEGs in complex oxide heterostructures, with a particular focus on 2DEGs that involve transport in SrTiO3. We discuss what is known about the electronic states in SrTiO3 2DEGs, both experimentally and theoretically. Examples from the current literature are summarized.

Self-assembled vertical heteroepitaxial nanostructures (VHN) in the complex oxide field have fascinated scientists for decades because they provide degrees of freedom to explore in condensed matter physics and design-coupled multifunctionlities. Recently, of particular interest is the perovskite-spinel-based VHN, covering a wide spectrum of promising applications. In this review, fabrication of VHN, their growth mechanism, control, and resulting novel multifunctionalities are discussed thoroughly, providing researchers a comprehensive blueprint to construct promising VHN. Following the fabrication section, the state-of-the-art design concepts for multifunctionalities are proposed and reviewed by suitable examples. By summarizing the outlook of this field, we are excitedly expecting this field to rise with significant contributions ranging from scientific value to practical applications in the foreseeable future.

Highly ordered mesoporous NiMoO4 material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2 adsorption-desorption, Raman and FT-IR. The mesoporous NiMoO4 with the coexistence of α-NiMoO4 and β-NiMoO4 showed well-ordered mesoporous structure, a bimodal pore size distribution and crystalline framework. The catalytic performance of NiMoO4 was investigated for oxidative dehydrogenation of propane. It is demonstrated that the mesoporous NiMoO4 catalyst with more surface active oxygen species showed better catalytic performance in oxidative dehydrogenation of propane in comparison with bulk NiMoO4.

We study the low temperature contribution to delayed recombination decay in several complex oxide scintillating crystals. We experimentally test the previously suggested hypothesis that the losses of fast scintillation light even at the lowest temperatures can be due to quantum effects. The results obtained for several material systems confirm that quantum tunneling between the luminescence center and a nearby defect is a good candidate for the origin of the observed phenomena.

Bismuth based complex oxides have attracted considerable interest due to their great potential to harvest solar light to solve the current environmental and energy crisis. Bismuth based complex oxides have excellent photo-oxidation ability for organic contaminant degradation and water oxidation via a photocatalytic process. Many efforts have been made to improve their photocatalytic performance, especially on the BiVO4, Bi2WO6 and Bi2MoO6 materials, which have been mostly studied in the past few years. Significant progress in understanding the fundamentals and improving the photocatalytic performance has been made due to the various new developed concepts and approaches in recent years. In this review, we present a comprehensive overview on the fundamentals and recent advances of BiVO4, Bi2WO6 and Bi2MoO6 photocatalysts. After the analysis of the structure–property relationships, the strategies that have been employed to enhance their photocatalytic performance are discussed in detail, including morphology control, surface modification, doping and construction of composite material. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of the highly efficient bismuth based complex oxide photocatalysts.

Oxide dispersion-strengthened (ODS) materials contain homogeneous dispersions of temperature-stable nano-oxides serving as obstacles for dislocations and further pinning of grain boundaries. The strategy for dispersion strengthening based on complex oxides (Y-Hf, -Zr, -Ce, -La) was developed in order to refine oxide dispersion to enhance the dispersion strengthening effect. In this work, the strengthening of EUROFER steel by complex oxides based on Y and elements of the IIIB group (lanthanum, scandium) and IVB group (cerium, hafnium, zirconium) was explored. Interparticle spacing as a dispersoid characteristic appeared to be an important factor in controlling the dispersion strengthening contribution to the yield strength of ODS EUROFER steels. The dispersoid size and average grain size of ODS EUROFER steel were altered in the ranges of 5&ndash, 13 nm and 0.6&ndash, 1.7 &micro, m, respectively. Using this strategy, the yield strength of the prepared alloys varied between 550 MPa and 950 MPa depending on the doping element.

The oxidation behaviors of Ni-16Cr-xAl (x=4.5%, 9.0%, mass fraction) superalloy foams in air at 1 000 °C were investigated. The effects of Al content on the resistance to high temperature oxidation were examined. The oxidation mechanisms of the foams were discussed. The results show that the resistance to the oxidation of the Ni-16Cr-xAl based alloy at 1 000 °C increases with the content of Al increasing from 4.5% to 9.0%. Complex oxide products are formed on the surface of the superalloy foams after the oxidation. Cr2O3 and Al2O3 are the predominant oxides for the scales of the foams with 4.5% Al and 9% Al, respectively. Excellent high temperature oxidation resistance and superior pore conformation stability for the Ni-16Cr-xAl based superalloy foam with 9% Al can be mainly attributed to the formation of relatively continuous and protective Al2O3 oxides on the surface of the foam.

Charged domain walls in ferroelectric thin films can be manipulated at the nanoscale and used to induce charges in the surrounding insulating material.

La0.3 Sr0.7 FeO3-δ films undergo dramatic changes in electronic and optical properties due to reversible oxygen loss induced by low-temperature heating. This mechanism to control the functional properties may serve as a platform for new devices or sensors in which external stimuli are used to dynamically control the composition of complex oxide heterostructures.

It was shown that the extraction pyrolysis method and the combined method of plasma electrolysis and extraction pyrolysis are suitable technologies for the formation of functional complex oxide composites exhibiting catalytic activity in CO conversion.

The range of recently discovered phenomena in complex oxide heterostructures, made possible owing to advances in fabrication techniques, promise new functionalities and device concepts. One issue that has received attention is the bistable electrical modulation of conductivity in ferroelectric tunnel junctions (FTJs) in response to a ferroelectric polarization of the tunnelling barrier, a phenomenon known as the tunnelling electroresistance (TER) effect. Ferroelectric tunnel junctions with ferromagnetic electrodes allow ferroelectric control of the tunnelling spin polarization through the magnetoelectric coupling at the ferromagnet/ferroelectric interface. Here we demonstrate a significant enhancement of TER due to a ferroelectrically induced phase transition at a magnetic complex oxide interface. Ferroelectric tunnel junctions consisting of BaTiO3 tunnelling barriers and La(0.7)Sr(0.3)MnO3 electrodes exhibit a TER enhanced by up to ~10,000% by a nanometre-thick La(0.5)Ca(0.5)MnO3 interlayer inserted at one of the interfaces. The observed phenomenon originates from the metal-to-insulator phase transition in La(0.5)Ca(0.5)MnO3, driven by the modulation of carrier density through ferroelectric polarization switching. Electrical, ferroelectric and magnetoresistive measurements combined with first-principles calculations provide evidence for a magnetoelectric origin of the enhanced TER, and indicate the presence of defect-mediated conduction in the FTJs. The effect is robust and may serve as a viable route for electronic and spintronic applications.

Thermal fatigue failure is one of the main failure forms of 8407 steel. Aiming at improving the anti-thermal-fatigue property of 8407 steel, the method of aluminization and subsequent oxidation is employed to form a complex oxide on the die surface. Thermal fatigue test was performed with the cycle heating method to compare thermal fatigue behaviors of 8407 steel samples with and without aluminization and oxidation treatment. In the test, thermal fatigue crack morphology formed on the surface was observed by scanning electron microscope (SEM) and then variations of initiating rate and propagating rate of main crack of thermal fatigue with cycles were investigated. Moreover, the thermal fatigue property was judged according to thermal fatigue main crack length and its reciprocal. Finally, the anti-thermal-fatigue mechanism of oxide film was clarified. The results show that the surface aluminization and oxidation treatment can improve both the initiating resistance and propagating resistance of thermal fatigue crack, which will improve the anti-thermal-fatigue property of 8407 steel.

Novel electronic and magnetic phases are being observed at interfaces between insulating, non-magnetic oxide compounds, with the most notable example being the interface between SrTiO3 and LaAlO3. The basic properties of these interfaces will be discussed, as well as prospects for applications and possible future developments.

The synthesis of transition metal heterostructures is currently one of the most vivid fields in the design of novel functional materials. In this paper we propose a simple scheme to predict \emph{band alignment }and \emph{charge transfer} in complex oxide interfaces. For semiconductor heterostructures band alignment rules like the well known Anderson or Schottky-Mott rule are based on comparison of the work function or electron affinity of the bulk components. This scheme breaks down for oxides due to the invalidity of a single workfunction approximation as recently shown (Phys. Rev. B 93, 235116; Adv. Funct. Mater. 26, 5471). Here we propose a new scheme which is built on a continuity condition of valence states originating in the compounds' shared network of oxygen. It allows for the prediction of sign and relative amplitude of the intrinsic charge transfer, taking as input only information about the bulk properties of the components. We support our claims by numerical density functional theory simulations as well as (where available) experimental evidence. Specific applications include i) controlled doping of SrTiO$_3$ layers with the use of 4$d$ and 5$d$ transition metal oxides and ii) the control of magnetic ordering in manganites through tuned charge transfer., Comments and suggestions are welcome

© 2016 American Chemical Society. Engineered topological spin textures with submicron dimensions in magnetic materials have emerged in recent years as the building blocks for various spin-based memory devices. Examples of these magnetic configurations include magnetic skyrmions, vortices, and domain walls. Here, we show the ability to control and characterize the evolution of spin textures in complex oxide micromagnets as a function of temperature through the delicate balance of fundamental materials parameters, micromagnet geometries, and epitaxial strain. These results demonstrate that in order to fully describe the observed spin textures, it is necessary to account for the spatial variation of the magnetic parameters within the micromagnet. This study provides the framework to accurately characterize such structures, leading to efficient design of spin-based memory devices based on complex oxide thin films.

Structure–property relationships are a key materials science concept that enables the design of new materials. In the case of materials for application in radiation environments, correlating radiation tolerance with fundamental structural features of a material enables materials discovery. Here, we use a machine learning model to examine the factors that govern amorphization resistance in the complex oxide pyrochlore (A2B2O7) in a regime in which amorphization occurs as a consequence of defect accumulation. We examine the fidelity of predictions based on cation radii and electronegativities, the oxygen positional parameter, and the energetics of disordering and amorphizing the material. No one factor alone adequately predicts amorphization resistance. We find that when multiple families of pyrochlores (with different B cations) are considered, radii and electronegativities provide the best prediction, but when the machine learning model is restricted to only the B = Ti pyrochlores, the energetics of disordering and amorphization are critical factors. We discuss how these static quantities provide insight into an inherently kinetic property such as amorphization resistance at finite temperature. This work provides new insight into the factors that govern the amorphization susceptibility and highlights the ability of machine learning approaches to generate that insight.