Spinel-type Structure Research Articles

Synthesis of cobalt ferrite nanoparticles from waste iron ore tailings and spent lithium ion batteries for photo/sono-catalytic degradation of Congo red

Cobalt ferrite nanoparticles were successfully synthesized by a combined coprecipitation method using recovered iron and cobalt from waste iron ore tailing and spent lithium ion batteries, respectively, characterized and utilized for photo/sono-catalytic degradation of Congo red. Characterizations by powder XRD, UV-DRS, SEM/TEM and surface area measurement revealed the formation of single phase spinel-type structure with average size 40–50 nm, surface area (36.2 m2/g), saturation magnetization (63 emu/g) and band gap energy (1.61 eV). XPS results showed that iron and cobalt in CoFe2O4 are present as Fe3+ and Co2+. It efficiently degraded CR dye under visible light and ultrasonic power for which the most probable degradation pathways were proposed. Recyclability tests showed the magnetic catalyst is reasonably stable, efficient and easily separated using an external magnet. Moreover, the present work gives further insight towards possible use of solid wastes in synthesis of value added materials in large scale for environmental applications.

Core@shell nanocomposites Fe7C3 / FexOy /C obtained by high pressure-high temperature treatment of ferrocene Fe(C5H5)2

The core@shell nanostructures were obtained in the process of transformation of ferrocene Fe(C5H5)2 at high pressure (HP) of 8 GPa and high temperature (HT) of 900 °C with an isothermal exposure time t varying from 10 to 10000 s. At t > 300 s, the iron carbide o-Fe7C3 nanoparticles with an orthorhombic crystal structure (sp.gr. Pnma) can be created, which are dispersed in highly defective carbon matrix. After opening the high-pressure cell, a series of redox reactions occurs, leading to a formation of iron oxides on the surface of the iron carbide core. When the size of Fe7C3 nanoparticle is less than critical one the nanoparticle is fully oxidized, while in the larger particle an amorphous iron oxide shell is formed. A sequential increase in t initiates crystallization processes both in the iron carbide subsystem and in the carbon subsystem, resulting in the formation of core@shell Fe7C3/FexOy/C structures. Iron oxides with a cubic spinel-type structure (Fe3O4/γ-Fe2O3) appear in the shell. However, under oxygen reduction, part of magnetite can be transformed into wüstite FeO. The magnetic properties of magnetite and wüstite are radically different, and by varying the thickness of these layers, structures with the desired functional properties can be obtained.

Preparation and effects of F-doping on electrochemical properties of Li4Ti5O12 as anode material for Li-ion battery

In this work, F-doped Li4Ti5O12 in the form of Li4Ti5O12-xFx (0 ≤ X ≤ 0.4) is successfully synthesized via a solid-state reaction between TiO2 (anatase), Li2CO3, and LiF. The synthesized powder is used as the anode in Li-ion batteries. X-ray diffraction (XRD) results show that the F−-doping does not change the spinel-type structure, and it has successfully doped into the crystal structure of Li4Ti5O12. The morphological and electrochemical characterization of synthesized powders is tested with the scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge techniques. Among the modified samples, Li4Ti5O11.7F0.3 delivers the highest capacity and cyclability. The Li4Ti5O11.7F0.3 (LTOF0.3) has a capacity of 139.7 and 134.7 mAh g−1 in the first and 100th cycles with 1 C, respectively. The retention of capacity after 100 cycles charge and discharge with 1 C for LTO and LTOF0.3 is 90.8 and 96.3%, respectively.

Preparation and electrocatalytic properties of (FeCrCoNiAl0.1)Ox high-entropy oxide and NiCo-(FeCrCoNiAl0.1)Ox heterojunction films

Abstract Multi-element (FeCrCoNiAl0.1)Ox high-entropy oxide (HEO) films are deposited by direct current (DC) reactive magnetron sputtering under different oxygen flow rates. The structure of the as-prepared (FeCrCoNiAl0.1)Ox films depends on the oxygen flow rate. When the oxygen flow rate is lower than 70%, (FeCrCoNiAl0.1)Ox is in the face-centered cubic (FCC) phase of the solid solution. When the oxygen flow rate reaches 80%, the prepared HEO film has a spinel-type solid solution structure, which is denoted as (Fe0.73Cr0.71Co0.78Ni0.81Al0.1)O4.01. After thermal annealing at temperatures from 500 to 700 °C under vacuum, a NiCo alloy precipitate appeared on the surface. The as-prepared (Fe0.73Cr0.71Co0.78Ni0.81Al0.1)O4.01 HEO film has an overpotential of 381 mV and shows an exceptional long-term electrolysis stability of 120 h in alkaline solutions at a current density of 10 mA cm−2. The oxygen evolution reaction (OER) catalysis of the NiCo-(FeCrCoNiAl0.1)Ox heterojunction film formed by annealing (Fe0.73Cr0.71Co0.78Ni0.81Al0.1)O4.01 at 700 °C is improved after 120 h of stability testing due to the synergetic effect between high-entropy oxide and NiCo. The present work not only provides a promising electrocatalyst but also broadens the application of high-entropy oxides.

Effect of Co content on magnetic features and SPIN states IN Ni–Zn spinel ferrites

The manuscript contains data on the effect of the Co content on the magnetic properties of Zn0·3Ni0·7Fe2O4 spinels, in which Ni2+ ions are partially substituted by Co2+ ions. Ferrites were produced via solid-state reaction from a mixture of oxides. All samples are single-phase with a spinel-type structure (SG: Fd-3m). The linear increase in the lattice parameters with increasing cobalt content was explained by the difference in ionic radii Co2+/Ni2+. The effect of the Co2+ content on the magnetic characteristics of Ni–Zn ferrites was established. Curie temperature decreased from 419 °C to 326 °C with increasing Co content from x = 0.0 to 0.7, respectively. At the same time, an increase in Ms; Mr and Hc was observed due to the larger magnetic moment of the Co2+ ion in comparison with Ni2+. Non-linear concentration dependence of the magnetic characteristics was discussed in terms of the Co2+ spin states.

The local structure around Ge atoms in Ge-doped magnetite thin films

AbstractDistribution of Ge atoms between tetrahedral and octahedral sites in the spinel-type structure of Fe2.64Ge0.36O4thin films fabricated by radio frequency sputtering with a composite target of magnetite and Ge has been investigated by extended X-ray absorption fine structure analysis. The local structural changes around the Ge atoms in the films induced by annealing at 573 and 873 K are discussed through comparison of the local structure for sintered crystalline Fe2.7Ge0.3O4in which Ge atoms preferentially located at the tetrahedral site of the spinel-type structure. This work provides successful information on the structural change with magnetic property of the thin films as follows: the Ge atoms statistically distributed at the tetrahedral and octahedral sites of the as-synthesized films and preferentially occupied the tetrahedral site by annealing at 873 K corresponding to the increase in magnetization.

Deltalumite, a New Natural Modification of Alumina with a Spinel-Type Structure

A new mineral, deltalumite, which is an analogue of the spinel-type synthetic δ-Al2O3, the second natural modification of alumina after corundum, α-Al2O3, has been found in products of two eruptions of the Ploskiy Tolbachik Volcano, Kamchatka, Russia. It occurs in the pores of basalt lava and basalt scoria altered by fumarolic gas. The mineral forms roundish segregations up to 0.2 mm across, which consist of blocky coarse prismatic individuals of up to 0.03 mm. Deltalumite is pale yellowish, pale beige, or white, translucent, with a vitreous luster. The mineral is brittle. Dcalc = 3.663 g/cm3. Deltalumite is optically uniaxial, negative, ω = 1.654(2), e = 1.653(2) (λ = 589 nm). The chemical composition (electron microprobe data) is, wt %: 99.74 Al2O3 and 0.04 SiO2; the total is 99.78. The strongest reflections of the powder X-ray diffraction pattern [d, A(I)(hkl)] are: 2.728(61)(202), 2.424(51)(212), 2.408(49)(213), 2.281(42)(206), 1.993(81)(1.0.11, 220, 221), 1.954(48)(0.0.12), and 1.396(100)(327, 400, 2.1.14). The mineral is tetragonal, with the P-4m2 space group (similar to synthetic δ-Al2O3). The unit-cell dimensions are a = 5.608(1), c = 23.513(7) A, V = 739.4(4) A3, and Z = 16. Deltalumite belongs to the spinel subgroup within the oxy-spinel group; its structural formula can be written as (Al0.67◻0.33)Al2O4, where ◻ is a vacancy. The new mineral can be clearly distinguished from other modifications of alumina using its powder X-ray diffraction pattern or IR spectrum.

Investigation of Solid Solution Ratio and Study for Crystal and Electronic Structure and Battery Properties of Spinel-Type αMgCo1.5Mn0.5O4-(1-α)Mg(Mg0.33V1.57Ni0.1)O4 for Mg Rechargeable Battery Cathode Materials

1. Introduction The Mg secondary battery of which a high volume energy densities is expected as the next generation secondary battery. However the Mg diffusion is difficult, and it don’t achieve to practical use. The previous study reported the cathode material MgCo2-xMnxO4 with spinel type structure (x= 0.5)1) and Mg (Mg0.33V1.67-yNiy)O4 (y= 0.1) 2) so far at our laboratory. The former cathode can exhibit a high initial discharge capacity. However, the capacity retention ratio is low. On the other hand, the latter cathode can exhibit high capacity retention ratio. This research was performed to determine synthetic method of solid solution cathode αMgCo1.5Mn0.5O4-(1-α) Mg(Mg0.33V1.57Ni0.1)O4 (α = 0.1, 0.3, 0.5, 0.7, 0.9) which is new cathode material and to measure battery characteristics for the purpose of utilizing an advantage of these materials.The electrode was characterized by the Rietveld analysis to reveal charge-discharge mechanism. 2. Experimental Three synthetic routes were examined to obtain the solid solution materials: (1) solid phase method (2) mechanochemical method and (3) reverse coprecipitation method. The synthesis method (1), mixed each endmembers by an agate mortar, and calcined.The synthesis method (2), mixed each endmembers and obtained a target materials by only the mechanical milling. The synthesis method (3), mixed each metal-nitrate aqueous solutions as it was α = 0.1, 0.3, 0.5, 0.7, 0.9, calcined to get a target materials.The obtained materials were identified by XRD,ICP-AES, and performed the charge-discharge cycle tests using three electrode cell. Synchrotron X-ray diffraction measurement (BL19B2, SPring-8) was performed and the average structure was analyzed by a Rietveld analysis (RIETAN - FP). Furthermore, XAFS (BL14B2, SPring-8) revealed pristine and charging/discharging electrode redox mechanism. 3. Result and discussion The sample synthesized by method (1) wasn’t assigned to spinel structure, while the samples synthesized by method (2) and (3) were assigned to spinel structure with the space group of Fd-3m from the powder X-ray diffraction. The sample of synthesis method (1) and (2), approximately controlled on a metal composition by ICP - AES. However, V composition of synthesis method (3) controlled smaller than preparation composition. Good fitting was obtained about a powder sample of a synthesis method (2) and (3) as a result of the Rietveld analysis, however, it revealed Mg occupied 8a/16d site for each sample.A charge-discharge cycle test was carried out at 90 ° C using a three-electrode cell.the sample of a synthesis method (2) performed 15 cycles by the discharge capacity of about 80 mAh/g, and the sample of method (3) (α =0.5) performed 24 cycles by the discharge capacity of about 100 mAh/g while the sample of method (3) (α =0,3) achieved 60 cycles at the discharge capacity of about 160 mAh/g and it had high capacity ratio (Fig.1). Acknowledgement This work was supported by JST ALCA-SPRING Grant Number JPMJAC1301, References 1) M. Ichiyama, N. Ishida, N. Kitamura, Y. Idemoto, the 86th Electrochemical Society of Japan Meet summary and 3O20 (2019).2) N. Kawakami, N. Ishida, N. Kitamura, Y. Idemoto, the 59th Battery forum summary P.375(2018). Figure 1

Isostructural metal hydrazones of 2-(methoxycarbonyl-hydrazono)-pentanedioic acid, H2L: Synthesis, cytotoxic activity of nano spinel ZnCo2O4 derived from single source precursor, [Zn1/3Co2/3(HL)2]·3H2O

Metal Schiff base [2-(methoxycarbonyl-hydrazono)-pentanedioic acid, H2L] complexes of type [M(HL)2]·3H2O, where M = Co (1), Zn (2) & Co-Zn (3), have been synthesized by condensation of α-ketoglutaric acid and methyl carbazate in the presence of divalent metal ions. A stoichiometric reaction of the Schiff base ligand with metal ions resulted in a solid solution precursor of [Zn1/3Co2/3(HL)2]. The crystal structures of metal and mixed metal (Zn-Co) complexes were isostructural and crystallized in monoclinic systems. The synthesized solid solution was employed as a precursor for preparing zinc cobaltite spinel (ZnCo2O4) nanoparticles. As-synthesized nanospinel cobaltite was characterized using Fourier-Transform Infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), and transmission electron microscopy (TEM) techniques. PXRD indicated that the product had a spinel type structure with high purity and a crystalline nature. The TEM images show that the spinels were constructed via self-assembled agglomeration of nanoparticles with irregular shapes. The elemental compositions and oxidation states of as-prepared ZnCo2O4 were further analyzed by X-ray photoelectron spectroscopy (XPS). Further, the cytotoxicity was determined against human breast adenocarcinoma (MCF-7) cancer cell lines at different concentrations using a thiazolyl blue tetrazolium bromide (MTT) assay. The spinel oxides prepared from the precursors showed promising results, demonstrating their clinical importance.

Innovative methodology for co-treatment of mill scale scrap and manganese ore via oxidization roasting-magnetic separation for preparation of ferrite materials

Mill scale scrap, which contains vast amounts of valuable metals, is a solid waste produced in the iron and steel industry. Conventional mill scale scrap treatment methods for metal extraction are characterized by high energy consumption and low value addition. In this study, co-treatment of mill scale scrap and manganese ore via the oxidization roasting-magnetic separation process was investigated for the synchronous preparation of higher-value materials and recovery of valuable metals. Thermodynamic and magnetism analyses indicated that a higher temperature (>1100 °C) and a MnO2/Fe2O3 molar ratio of 0.75–1 are essential for the preparation of manganese ferrite. The experimental validation revealed that soft magnetic manganese ferrite powders with a purity of 97.5 wt% were obtained when the test was conducted at 1300 °C for 120 min, followed by a two-stage grinding and magnetic separation process; the corresponding yield and the Mn and Fe recoveries were 78.99 wt%, 86.14 wt%, and 84.60 wt%, respectively. During the oxidization process, [Fe2+]O was initially oxidized to the anti-form spinel-type structure of [Fe3+][Fe2+Fe3+]O4, and thereafter, it reacted with the decomposition product of [Mn3+][Mn2+Mn3+]O4 to form a hybrid spinel-type structure [Me2+xMe3+l-x][Me2+1-xMe3+1+x]O4 (Me refers to Mn and Fe) via the Mn2+/Fe2+/Mn3+/Fe3+ ions exchange at the tetrahedral and octahedral sites. Moreover, the as-purified ferrite can be used as an ingredient for the preparation of high-performance MnZn ferrite.

Photocatalytic performance of β-Ag2MoO4 microcrystals at different experimental conditions

In this present work, we report the photocatalytic activity of microcrystals of silver molybdate (β-Ag2MoO4) synthesized at 120 °C for 2 h by hydrothermal method. These microcrystals have been structurally characterized by X-ray diffraction (XRD), Rietveld refinement and micro-Raman (MR). The optical properties and the structure of the band gap were studied using diffuse reflectance spectroscopy of UV–vis (UV–vis) and photoluminescence (PL). The morphology and semiquantitative analysis of elements were investigated by field emission scanning electron microscopy (FE-SEM) images. The photocatalytic properties of these microcrystals have been investigated in the degradation of rhodamine B (RhB) and methyl orange (MO) dyes under UV-light. XRD patterns, Rietveld refinement data and Raman spectrum indicate that all microcrystals exhibit spinel-type cubic structure with space group of Fd3¯m and point group of symmetry O7h composed by tetrahedral [MoO4] and distorted octahedral [AgO6] clusters. The optical band gap found was Egap =3.30 eV for β-Ag2MoO4 microcrystals, associated with the indirect allowed electronic transitions. FE-SEM images have revealed that microcrystals have potato-like morphology. The photoluminescent properties (PL) verified can be explained by the distortions of the clusters present in the structure of β-Ag2MoO4 microcrystals. Moreover, these microcrystals exhibit high photocatalytic performance at pH > 8. Where, the photo-induced holes (h+) are one of the main reactive species involved in the degradation of RhB and MO dyes.

Influence of magnesium doping on structural and elastic parameters of Nickel Zinc nanoferrites

The Ni0.45 Zn0.55-xMgxFe2O4 (x = 0.0, 0.1, 0.2 and 0.3) nanoferrites were synthesized by the sucrose method. The prepared nanoferrites were characterized by XRD, TEM, FTIR and Raman techniques. The XRD studies verified the cubic spinel-type structure of the samples. The lattice constant, particle size, bond lengths, X-ray density were determined. The lattice constant decreased as Magnesium content increased. The SAED image shows a ring pattern that establishes polycrystalline state of ferrites. The TEM image reveals a spherical shape of nanoferrite particles. The elastic parameters were calculated for obtained nanoferrites using FTIR data. The moduli of elasticity and Debye temperature decreased with increase in Magnesium content. Five first order Raman active modes were revealed by Raman Spectroscopy.

RAMAN CHARACTERIZATION OF CuIrSnX4 NORMAL-SPINEL SYSTEMS

CuIrSnS4, CuIrSnSe4 and CuIrSnS2Se2 were synthetized by a solid-state reaction at 700 °C. Powder X-ray diffraction patterns were consistent with normal spinel-type structure. Scanning electron microscopy (SEM-EDS) images showed a uniform distribution of CuIr-Sn-S and Se atoms in the samples. Raman scattering analysis revealed A1g, Eg, and three F2g vibrational modes in spectra (cubic Fd3m space-group). Signal at ~320 cm-1 corresponded to the A1g mode, while the band at  230 cm-1 was assigned to the F2g(2) mode due to the asymmetric stretching of the Cu-X bond. Raman spectra were compared with those of the previously published thio- and selenospinels.

High performance electrospun nickel manganite on carbon nanofibers electrode for vanadium redox flow battery

A composite material based on nickel manganite and carbon nanofibers (NiMn2O4/CNF) is synthesized by electrospinning method and investigated as a symmetric electrode for vanadium redox flow battery (VRFB). The X-ray diffraction pattern shows the formation of NiMn2O4/CNF, characterized by a cubic spinel-type structure and a high graphitization degree of the carbon nanofiber. XPS analysis reveals the presence of mixed oxidation state of nickel and manganese as Ni2+/Ni3+ and Mn2+/Mn3+, respectively. As evident by scanning electron microscope analysis (SEM), a complete covering of carbon nanofibers surface by NiMn2O4 nanoparticles occurs. Charge-discharge curves are carried out from 80 mA/cm2 up to 500 mA/cm2. The best result shows an energy efficiency (EE) of about 68% with corresponding deep of discharge (DoD) of about 55% at 500 mA/cm2. The high electrical conductivity as well as the high hydrophilicity, useful for improving the active surface area utilization, could be responsible for the remarkable results of the electrospun electrodes. In fact, thanks to the structural defects of the NiMn2O4/CNF and the presence of hydroxyl (OH), carboxyl (COOH) and nitrogen functional groups, the electrocatalytic activity increases at the electrode/electrolyte interface. Therefore, a remarkable power density at very high current density was achieved, 550 mW/cm2 at 500 mA/cm2.

New compounds of the Li2 MSn3S8 type

Abstract The substitution of Cu/Ag by lithium in complex thiospinels with the general formula A I 2 B II C IV 3 X VI 8 was achieved by ball milling and a subsequent annealing step in an atmosphere of H2S. Four hitherto unknown compounds Li2 MSn3S8 with M = Mg, Mn, Fe, Ni were obtained without side phases and have been structurally investigated. From X-ray powder diffraction experiments, space group Fd 3 ¯ $\overline{3}$ m and a spinel-type structure are suggested. In these so-called normal spinels, lithium occupies one eighth of the tetrahedral voids (Wyckoff position 8a) of the cubic closest packing of the sulfide ions whereas M and Sn can be found on one half of the octahedral voids (Wyckoff position 16d).

Crystallographic Analysis of Boro- and Alumosilicates with the Structures Similar to the Structures of Analcime and Pollucite

For the cubic structures of analcime Na1.71(Al1.8,Si4.2)O12·2H2O, pollucite CsAlSi2O6 and tetragonal (but pseudo-cubic) kirchhoffite CsBSi2O6 and leucite KAlSi2O6 the common stencil (pattern) of cation arrangement at the key positions of symmetry space groups related with configurations in spinel, diamond, garnet, and other structure types is determined. For the mutual ordering of the positions of large cations with anions the presence of two sublattices related by a pseudo-sixfold axis in the diffraction (reciprocal) space is shown.

Resistance-Temperature Characteristics of Cr Doped Ni<sub>0.7</sub>Mn<sub>2-x</sub>Cu<sub>0.3</sub>Cr<sub>x</sub>O<sub>4</sub> NTC Thermistors

Manganese-based solid solution ceramics of transition metal with spinel-type crystal structure have generated much interest as NTC thermistors in various domestic and industrial applications. Doping has been considered as one of the most important method to improve their electrical properties. In this work, Cr doped Mn-based solid solution NTC ceramics Ni0.7Mn2-xCu0.3CrxO4 (x = 0.1, 0.2, 0.3 and 0.4) were prepared by solid-state reaction method. X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (EDS) were applied to study the phase structure, surface morphology and surface element content. The results indicate that the resistance and B value increase as the substituted Cr content increases.

Probing the structural and magnetic properties of small crystalline nickel ferrite nanoparticles near the upper size limit of the single-domain regime

ABSTRACTNickel ferrite nanocrystalline particles were prepared by hydrothermal method. A systematic study was carried out on their structural and magnetic properties in wide ranges of temperatures and magnetic fields. The prepared nanoparticles were investigated by XRD, TEM, FTIR, and VSM. The results of Rietveld refinement revealed that the nanoparticles have a cubic single phase spinel type structure. The TEM measurements showed that the nanoparticles were monodisperse and spherical in shape. The FTIR results confirmed the single phase nature of the prepared nanoparticles. The magnetic measurements showed that the nanoparticles were ferromagnetic over a wide temperature range. The saturation magnetisation and the first anisotropy constant were observed to increase with reducing temperature. The estimated size of a single magnetic domain was found to be around 13 nm, which is three times smaller than the estimated crystallite size found from XRD, confirming that the average size of the nanoparticles was located above the critical size of the single-domain regime.

The Design of Nano/Micro Structure of the Composite Metal Oxides and the Gas Sensing Performances

The gas sensor based on metal oxide semiconductors (MOS), which is known as one of the most widely popular gas sensors, plays an important role in gas detection in all walks of life. The sensing principle of MOS-based gas sensors results from changes in resistance caused by the adsorption–desorption reaction between target gases and chemisorbed oxygen ions on the surface of the sensing layers [1-3]. To generate adjustable oxygen vacancies on the surfaces of MOS is an effective strategy to improve the gas sensing performances [4, 5]. This work reported the synthesis of spinel type cobalt-based MOS (MCo2O4, M=Zn, Ni and Mn) (Fig. 1(a)) and the performance optimization by controlling the stoichiometric proportion of sensing materials. The results show that sensing properties can be significantly enhanced by substituting Co with other transition metals in the lattices. ZnCo2O4 with typical normal spinel structure can be regarded as a representative sensing material among the studied cobaltates, which exhibits the best sensing performances to acetone. The sensitivity of the ZnCo2O4 sensor is 24 and 106 times higher than those of the NiCo2O4-sensor and MnCo2O4-sensor at 190 °C, respectively. Zn substitution in tetrahedrally coordinated positions can provide more adsorbed oxygen molecules and oxygen vacancies and enable a better gas-sensing capability (Fig. 1(b-d)). In addition, the transition metal content can also be adjusted to further increase oxygen vacancy. The Zn content was controlled in ZnxCo3-xO4 bimetallic oxides during the growth process. When tested as an acetone sensing layer for gas sensors, the prepared ZnxCo3-xO4 materials (Zn/Co=0.37) composed of nano-sized building blocks exhibited a response of 35.6 to 200 ppm acetone within 60 s (Fig. 1(e)). In addition, the sensor device also demonstrates a low detection limit of 0.5 ppm to acetone, even in a high humidity environment. The better acetone sensing performance is attributed to the adsorbed oxygen and abundant oxygen vacancies of ZnCo-0.37 samples. More adsorbed oxygen molecules that take part in the sensing reaction are beneficial for the release of a mass of electrons to increase the extent of the change in resistance. Oxygen vacancies, serving as electron donors, endow ZnCo-n nanocages with unpaired electrons to provide free electrons and active sites to enhance the gas sensing properties. This approach sheds light on the rational design of bimetallic oxides with abundant oxygen vacancy and the development of superior sensors targeted for ultratrace acetone gas.

Discovery of Ternary Silicon Titanium Nitride with Spinel-Type Structure

Here we report on the discovery of a ternary silicon titanium nitride with the general composition (Si1−x,Tix)3N4 with x = 0 < x < 1 and spinel-type crystal structure. The novel nitride is formed from an amorphous silicon titanium nitride (SiTiN) precursor under high-pressure/high-temperature conditions in a large volume high-pressure device. Under the conditions of 15–20 GPa and 1800–2000 °C, spinel-type γ-Si3N4 and rock salt-type c-TiN are formed. In addition, crystals of the discovered nano-sized ternary phase (Si1−x,Tix)3N4 embedded in γ-Si3N4 are identified. The ternary compound is formed due to kinetically-controlled synthesis conditions and is analyzed to exhibit the spinel-type structure with ca. 8 atom% of Ti. The Ti atoms occur in both Ti3+ and Ti4+ oxidation states and are located on the Si sites. The ternary nano-crystals have to be described as (Si,Ti)3N4 with N-vacancies resulting in the general composition (Si4+1−x Ti4+x-δTi3+δ)3N4-δ.