High-pressure synthesis and local structure of corundum-type In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.7)

The corundum-type In(2-2x)Zn(x)Sn(x)O(3) solid solution (cor-ZITO, x ≤ 0.7) was synthesized at 1000 °C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO(3). Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO(3)-type arrangement.     

Structural and electrical properties of sol–gel grown (1 − x) (ZnO) + (x) (SnO2) (x = 0, 0.25, 0.5) nanocomposites

Journal of Sol-Gel Science and Technology - Semiconducting oxide nanocomposites of ZnO/SnO2 with different weight ratio, i.e. (i) ZnO:SnO2?=?100:0 (ZnO0), (ii)...     

Phosphates M 0.5(1 + x) 2+ Cr x Ti2 − x (PO4)3: Synthesis, structure, and catalytic properties

Complex phosphates of titanium, chromium, and metals(2+) of the general formula M_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ (M = Mg, Ca, Mn, Ni, Sr, Ba, and Pb) were synthesized. Their phase formation was studied by means of X-ray powder diffraction, electron probe microanalysis, differential thermal analysis, and IR spectroscopy. Individual phases and solid solutions crystallizing in kosnarite and langbeinite structure types were identified; their crystallographic parameters were calculated. The catalytic properties of phosphates Ca_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ in methanol conversion were studied.     

Electroconductance of single-crystal Li2 + x Fe 2 − 2x 2+ Fe x 3+ (MoO4)3 (x = 0.22)

Electrophysical properties of single-crystal Li_{2 + x} Fe _{2 ? 2x} ²⁺ Fe _x ³⁺ (MoO₄)₃ (x = 0.22) are studied at 25–400°C. It is found that the conduction is of electronic nature and the conductivity equals 5 × 10^-2 S/cm at 300°C. The activation energy for the electron transport is 0.23 eV. The conductance in molybdate Li_2.22Fe _1.56 ²⁺ Fe _0.22 ³⁺ (MoO₄)₃ is markedly anisotropic.     

Rubidium-cationic conductivity of Rb2−2x Ga2−x A x O4 (A = P, V, Nb, Ta) solid electrolytes

Solid solutions based on rubidium monogallate RbGaO₂ with a general formula Rb_2?2x Ga_2?x A _x O₄ (A = P, V, Nb, and Ta) are synthesized. Their crystal structure and temperature and concentration dependences of conductivity are studied. The highest rubidium-cationic conductivity is (1.8–3.9) × 10^?3 S cm^?1 at 400°C and (1.4–2.1) × 10^?2 S cm^?1 at 700°C. These results are compared with the data for rubidium monogallate doped with four-charged cations and solid solutions based on RbAlO₂.     

Effect of hydration on conductivity of Ba4La x Ca2 − x Nb2O11 + 0.5x (x = 0.5, 1, 1.5, 2) phases

Substitution of Ca by La in initial cubic double perovskite Ba₄(Ca₂Nb₂)O₁₁[VO]₁ allowed obtaining phases with a similar structure with a lower content of structural oxygen vacancies, Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} [VO]_{1 ? 0.5x} (x = 0.5, 1, 1.5, 2). The impedance technique was used to measure the temperature dependences of conductivity in the atmosphere of dry and humid air. Transport numbers determined using the EMF method in an oxygen-air and water steam concentration cells point to the predominantly hole nature of conductivity in the high-temperature region (T > 600°C) and to predominance of proton conductivity in the low-temperature region. Activation energies of hole and proton conductivity were calculated. Thermogravimetric measurements were carried out under heating from 25 to 1000°C with simultaneous mass-spectrometric determination of evolved H₂O and CO₂. The properties of the studied Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} (x = 0.5, 1, 1.5, 2) phases were compared with the earlier studied Ba_{4 ? x} La _x (Ca₂Nb₂)O_{11 + 0.5x} phases with similar lanthanum content.     

Glycolate Ti1 − x Fe x (OCH2CH2O)2 − x/2 as a precursor for the preparation of quasi-one-dimensional (1D) solid solutions Ti1 − x Fe x O2 − 2x/2 (0 ≤ x ≤ 0.1)

Quasi-one-dimensional (1D) solid solutions Ti_{1 ? x} Fe _x (OCH₂CH₂O)_{2 ? x/2} (0 < x ≤ 0.1) with the structure of anatase were prepared by heating the glycolate Ti_{1 ? x} Fe _x (OCH₂CH₂O)_{2 ? x/2} in an atmosphere of air at a temperature of >450°C. The conditions of formation and the properties of the new glycolate Ti₃Fe₂(OCH₂CH₂O)₉ were described. It was found that the synthesized Ti_{1 ? x} Fe _x O_{2 ? 2x/2} solid solutions exhibit photocatalytic activity in the reaction of hydroquinone oxidation in an aqueous solution on irradiation with UV light. A correlation between the rate of oxidation of hydroquinone and the concentration of iron in the catalyst was established. A procedure for the preparation of titanium dioxide with the structure of anatase doped with iron and carbon (Ti_{1 ? x} Fe _x O_{(2 ? x/2) ? yCy)} and also composites on its basis, which contain an excess amount of carbon, was proposed.     

Formation of (C x H2x+1)4NBr·nH2O (x = 1–3) hydrate

The phase diagram of the binary system tetramethylammonium bromide-water was studied by the differential thermal analysis. In the stable region two phases, ice and the salt itself, were detected, and in the metastable region, three tetramethylammonium bromide hydrates (bromide-water, 1 : 4, mp 68.8°C, 1 : 5, mp 36.0°C, 1 : 7.5, mp ?19.5°C) were found. Formation of (C _x H_2x+1)₄NBr·nH₂O (x = 1–3, n = 4, 5, 7.5) hydrates was revealed.     

Crystal structural, magnetic, and transport properties of layered cobalt oxyfluorides, Sr2CoO(3+x)F(1-x) (0 ≤ x ≤ 0.15)

The crystal structure of the layered cobalt oxyfluoride Sr(2)CoO(3)F synthesized under high-pressure and high-temperature conditions has been determined from neutron powder diffraction and synchrotron powder diffraction data collected at temperatures ranging from 320 to 3 K. This material adopts the tetragonal space group I4/mmm over the measured temperature range and the crystal structure is analogous to n = 1 Ruddlesden-Popper type layered perovskite. In contrast to related oxyhalide compounds, the present material exhibits the unique coordination environment around the Co metal center: coexistence of square pyramidal coordination around Co and anion disorder between O and F at the apical sites. Magnetic susceptibility and electrical resistivity measurements reveal that Sr(2)CoO(3)F is an antiferromagnetic insulator with the Néel temperature T(N) = 323(2) K. The magnetic structure that has been determined by neutron diffraction adopts a G-type antiferromagnetic order with the propagation vector k = (1/2 1/2 0) with an ordered cobalt moment μ = 3.18(5) μ(B) at 3 K, consistent with the high spin electron configuration for the Co(3+) ions. The antiferromagnetic and electrically insulating states remain robust even against 15%-O substation for F at the apical sites. However, applying pressure exhibits the onset of the metallic state, probably coming from change in the electronic state of square-pyramidal coordinated cobalt.     

Novel red-emitting phosphors, (Mg(1−x−y)MnxDyy)Al2Si2O8 and (Mg(1−x−y)MnxTmy)Al2Si2O8

Mn⁴⁺ doped and Dy³⁺, Tm³⁺ co-doped MgAl₂Si₂O₈-based phosphors were prepared by conventional solid state reaction at 1,300 °C. They were characterized by thermogravimetry, differential thermal analysis, X-ray powder diffraction, photoluminescence, and scanning electron microscopy. The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600–715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the ²E → ⁴A₂ transitions of Mn⁴⁺.     

Sol-gel synthesis and structure of MZr2(AsO4)3 arsenates and MZr2(AsO4) x (PO4)3 − x arsenate phosphates (M = K,Rb, Cs)

MZr₂(AsO₄)₃ arsenates and MZr₂(AsO₄) _x (PO₄)_{3 ? x} arsenate phosphates (M = K, Rb, Cs) have been obtained by sol-gel synthesis followed by heat treatment and have been characterized by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Continuous series of substitutional solid solutions form in the MZr₂(AsO₄) _x (PO₄)_{3 ? x} systems (0 ≤ x ≤ 3). The solid solutions have a kosnarite structure (KZr₂(PO₄)₃, space group \(R\bar 3c\) ). The crystal structures of MZr₂(AsO₄)₃ and MZr₂(AsO₄)_1.5(PO₄)_1.5 have been refined by full-profile analysis. The structural frameworks of these phases are built from ZrO₆ octahedra and AsO₄ tetrahedra or (As,P)O₄ tetrahedra statistically populated by arsenic and phosphorus atoms. The alkali metal atoms occupy extraframework sites. The effect of the crystal chemical properties of alkali metals on the formation of the structures of MZr₂(AsO₄)₃ arsenates (M = Li-Cs) and MZr₂(AsO₄) _x (PO₄)_{3 ? x} solid solutions is discussed.     

[M(dap)3]2(Sb2Se5)·xH2O(M=Ni,x=2;M=Zn,x=0)的溶剂热合成及晶体结构

利用溶剂热法合成了2种新的有机杂化锑硒化合物[Ni(dap)3]2(Sb2Se5)].2H2O(1)和[Zn(dap)3]2(Sb2Se5)](2)(dap=1,2-丙二胺),单晶X射线衍射分析结果表明,1属于三方晶系,P3121空间群,晶胞参数为a=10.7574(14),b=10.7574(14),c=31.672(4),γ=120.00°,z=4。2属于单斜晶系,P21空间群,晶胞参数为a=10.772(2),b=16.391(3),c=11.704(2),β=100.912(4)°,z=4。在2种化合物中,Ni2 与Zn2 离子分别与3个dap配体螯合形成畸变八面体几何构型,其中dap配体的N原子是无序的,而二聚[Sb2Se5]2-阴离子是由2个SbSe3三角锥共用1个Se原子连接而成。     

Homoleptic diphosphacyclobutadiene complexes [M(η(4)-P2C2R2)2]x- (M = Fe, Co; x = 0, 1)

The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands are reported. Compounds [K([18]crown-6)(thf)(2)][Fe(η(4)-P(2)C(2)tBu(2))(2)] (K1), [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)tBu(2))(2)] (K2), and [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)Ad(2))(2)] (K3, Ad = adamantyl) were obtained from reactions of [K([18]crown-6)(thf)(2)][M(η(4)-C(14)H(10))(2)] (M = Fe, Co) with tBuC[triple bond]P (1, 2), or with AdC[triple bond]P (3). Neutral sandwiches [M(η(4)-P(2)C(2)tBu(2))(2)] (4: M = Fe 5: M = Co) were obtained by oxidizing 1 and 2 with [Cp(2)Fe]PF(6). Cyclic voltammetry and spectro-electrochemistry indicate that the two [M(η(4)-P(2)C(2)tBu(2))(2)](-)/[M(η(4)-P(2)C(2)tBu(2))(2)] moieties can be reversibly interconverted by one electron oxidation and reduction, respectively. Complexes 1-5 were characterized by multinuclear NMR, EPR (1 and 5), UV/Vis, and M?ssbauer spectroscopies (1 and 4), mass spectrometry (4 and 5), and microanalysis (1-3). The molecular structures of 1-5 were determined by using X-ray crystallography. Essentially D(2d)-symmetric structures were found for all five complexes, which show the two 1,3-diphosphacyclobutadiene rings in a staggered orientation. Density functional theory calculations revealed the importance of covalent metal-ligand π bonding in 1-5. Possible oxidation state assignments for the metal ions are discussed.     

Phase Evolution and Magnetic Properties of Sn_(1-2x)Fe_xNb_xO_2(0.45≤x≤0.50)

Sn1-2xFexNbxO2(0.45≤x≤0.50) samples were prepared at 1000 ℃ via a simple chemical co-precipitation method.The effects of the concentrations of Sn doped on the structures and magnetic properties of the samples have been investigated.A systematic variation from monoclinic to orthorhombic FeNbO4 structure was observed with increasing Sn content.The phase evolutions were observed from monoclinic structure with x=0.50 to the coexistence of monoclinic and orthorhombic structures with x=0.48,0.47,0.46,and then to orthorhombic structure with x=0.45.Antiferromagnetic behavior was observed for all the samples,and the magnetic ordering temperatures decrease with increasing Sn concentration,which further indicated the sequence of phase transitions.The results suggest that the incorporation of Sn can stabilize the orthorhombic FeNbO4.     

Electroconductivity of Solid Solutions Cs3–2x M x PO4 (M = Ba, Sr, Ca, Mg)

Solid solutions Cs_{3 – 2x} M _x PO₄ (M = Ba, Sr, Ca, Mg) are synthesized and their thermal behavior and electroconductivity are examined. Adding elements of Subgroup IIA of the periodic table into cesium orthophosphate shifts the phase transition, which occurs in pure Cs₃PO₄ at 450–620°, towards lower temperatures and raises the cesium cation conductivity at low temperatures. The electroconductivity of a high-temperature modification of Cs₃PO₄ is weakly dependent on the presence and concentration of such additives, which points to structural disordering of the cesium sublattice.     

Synthesis and Ionic Conductivity of LiZr2(VO4)x(PO4)3 – x

Russian Journal of Electrochemistry - Vanadate phosphates LiZr2(VO4)x(PO4)3 – x are synthesized by the sol-gel technique with subsequent annealing and studied using X-ray diffraction...     

Kinetics of phase transition and thermal stability in Se80?x Te20Zn x (x?=?2, 4, 6, 8, and 10) glasses

Se_80?x Te₂₀Zn _x (x?=?2, 4, 6, 8, and 10) glasses have been prepared using conventional melt quenching technique. The kinetics of phase transformations (glass transition and crystallization) have been studied using differential scanning calorimetry (DSC) under non-isothermal condition at five different heating rates in these glasses. The activation energy of glass transition (E _t), activation energy of crystallization (E _c), Avrami exponent (n), dimensionality of growth (m), and frequency factor (K _o) have been investigated for the better understanding of growth mechanism using different theoretical models. The activation energy is found to be highly dependent on Zn concentration. The rate of crystallization is found to be lowest for Se₇₀Te₂₀Zn₁₀ glassy alloy. The thermal stability of these glasses has been investigated using various stability parameters. The values of these parameters were obtained using characteristic temperatures, such as glass transition temperature T _g, onset crystallization temperature T _c, and peak crystallization temperature T _p. In addition to this, enthalpy-released during crystallization has also been determined. The values of stability parameters show that the thermal stability increases with the increase in Zn concentration in the investigated glassy samples.     

Synthesis of Calcium Phosphates by PO(OH)x(OBut)3−x and CaO2C2H4

In this work, an alkoxide solution route to synthesize Ca phosphates was developed. For the precursors, a CaO₂C₂H₄ solution was prepared by dissolving Ca metal powder into ethylene glycol, and a PO(OH)_x(OBut)_3–x solution was prepared by dissolving P₂O₅ inton -butanol under reflux conditions. In order to obtain a mixed solution of the two precursors, acetic acid was used as an additive. The experimental results show that (1) -2CaO · P₂O₅, -3CaO · P₂O₅, and hydroxyapatite can be easily synthesized by converting the corresponding mixed solutions to powder products in a hot plate, and calcining the as prepared products at 1100°C; (2) acetic acid behaves as a good agent for controlling the reactions between the two precursors by modifying the CaO₂C₂H₄ species in solution and decreasing the reactivity of the PO(OH)_x(OBut)_3–x species.     

喷雾干燥法制备Li_(1.2)Mn_(0.4+x)Ni_xCr_(0.4-2x)O_2及其结构与电化学特征

利用喷雾干燥法合成了富锂三元正极材料Li1.2Mn0.4+xNixCr0.4-2xO2(x=0,0.05,0.10,0.15,0.20,以下简称为SD1~SD5),并利用XRD,XPS,ICP,TEM,SEM等手段对材料进行结构,元素价态,形貌及电化学性能等方面的表征。SD1~SD5系列样品都具有层状结构,其所含的Cr元素为Cr6+和Cr3+共存,而Ni元素价态为+2.5价,Mn元素为+4价。SD1~SD4样品中由于存在非晶态的Li2CrO4,导致样品表现出强烈的吸湿性。这个问题可通过水洗处理来解决,且水洗处理对于改善该系列材料的电化学性能有明显的效果。SD1~SD5系列样品中,SD1与SD4样品电化学性能较好,以20 mA.g-1的放电电流密度,在4.8~2.0 V电压区间内,首次放电比容量分别为247和220 mA.h.g-1,经过20次充放电循环后,容量保持率分别为73%和78%。高温条件下SD1和SD4样品的首次放电比容量分别增大为256和237 mA.h.g-1,经过20次充放电循环后容量保持率分别为83%和99%。将充放电电压扩展为5.0~2.0 V时,SD4样品首次放电比容量可以达到307 mA.h.g-1。     

水热法制备富锂型Li_(2+4x)Mn_(0.6+2x)Ni_(0.6-6x)Cr_(0.8)O_4及其结构与电化学特性

采用水热法制备了系列富锂尖晶石型正极材料Li2+4xMn0.6+2xNi0.6-6xCr0.8O4(x=1/30,1/20,1/15,1/12),通过X射线衍射(XRD)、电感耦合等离子体-原子发射光谱(ICP-AES)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FTIR)、拉曼光谱、循环伏安(CV)和充放电测试等手段对其结构及电化学性能进行表征.结果表明,所制备的系列材料为富锂型高电压尖晶石结构正极材料,该系列样品在4.7 V左右有放电平台.x=1/15和x=1/12时,样品中的Cr为+3价,没有观测到Cr6+.随着x值的增大,样品中Li离子与过渡金属离子的混排减小,样品的充放电比容量逐渐增大,且2.7 V处的放电平台容量也增加.当x=1/12时,样品具有较好的充放电比容量和倍率特性,首次放电比容量为107.3 mA·h/g,20次循环后容量保持率为84.9%.