Synthesis,structure, and conduction of solid solutions BIMEVOX (Me = Cu,Ti)

Conditions for synthesizing single-phase solid solutions Bi₄V_{2 ? x} Cu _x/2Ti _x/2O_{11 ? x} and Bi_{4 ? x/2}V_{2 ? x/2}Cu _x/2Ti _x/2O_{11 ? x/2} are studied. The sequence of phase transformations is determined. Possible domains of stability of polymorphic modifications and the overall conductivity as a function of temperature and composition are studied. The structure of the γ-modification is refined using Rietveld’s full-profile analysis.     

Effect of Ti substitution on hydrogen storage properties of Zr1−xTixCo (x = 0, 0.1, 0.2, 0.3) alloys

Zr_1−xTi_xCo (x = 0, 0.1, 0.2, 0.3) alloys were prepared by arc-melting method and the effect of Ti substitution on hydrogen storage properties was studied systematically. Hydrogen desorption pressure-composition-temperature (PCT) measurements were carried out using Sievert's type volumetric apparatus for ZrCo (at 473 K, 573 K and 673 K) and Zr_1−xTi_xCo alloys (at 673 K), respectively. Products after dehydrogenation were characterized by X-ray diffraction (XRD). In addition, the kinetics of Zr_1−xTi_xCo hydride was investigated at 473 K and 673 K, respectively, under hydrogen pressure of 5 MPa. Results showed that Ti substitution for Zr did not change the crystal structure of ZrCo phase. With the increase of temperature from 473 K to 673 K, the extent of disproportionation for ZrCo alloy increased. With Ti content increasing at 673 K, the desorption equilibrium pressure of Zr_1−xTi_xCo-H₂ systems elevated and the disproportionation reaction of Zr_1−xTi_xCo alloys was inhibited effectively. Ti substitution decreased the kinetics rate and the effective hydrogen storage capacity of Zr_1−xTi_xCo alloys slightly. Generally speaking, it was found that Zr_0.8Ti_0.2Co alloy had better anti-disproportionation property with less decrease of effective hydrogen storage capacity which was beneficial to tritium application in the International Thermonuclear Experimental Reactor (ITER).     

Synthesis and crystal structure of Ln2MGe4O12, Ln=rare-earth element or Y; M=Ca, Mn, Zn

The crystal structure of the promising optical materials Ln₂M²⁺Ge₄O₁₂, where Ln=rare-earth element or Y; M=Ca, Mn, Zn and their solid solutions has been studied in detail. The tendency of rare-earth elements to occupy six- or eight-coordinated sites upon iso- and heterovalent substitution has been studied for the Y_2−xEr_xCaGe₄O₁₂ (x=0-2), Y_2−2xCe_xCa_1+xGe₄O₁₂ (x=0-1), Y₂Ca_1−xMn_xGe₄O₁₂ (x=0-1) and Y_2−xPr_xMnGe₄O₁₂ (x=0-0.5) solid solutions. A complex heterovalent state of Eu and Mn in Eu₂MnGe₄O₁₂ has been found.     

Structural,magnetic and transport properties of S doping in Sr2FeMoO6 compound

The polycrystalline Sr₂FeMoO_6-xS_x (0.0 ≤ x ≤ 0.4) series were synthesized. The structure of Sr₂FeMoO_6-xS_x is assigned to tetragonal system with space group I4/mmm. The cell volume decreases with x from 0.0 to 0.3, then, increases with x from 0.3 to 0.4. S doping leads the oxygen/sulfur at 4e and 8h positions to movement away from Fe and to displacement toward Mo, respectively. The M_S at room temperature increases with degree of order of Fe and Mo ions. The electrical resistivity for studied samples exhibits a semiconductor-like behavior. The resistivity decreases with S doping. The electrical transport behavior is mainly dominated by electron-electron interactions except x = 0.4 in 0.0 magnetic field.     

Phase diagrams in the quaternary systems M1−xCuxCr2X4 with M = Cd,Mn, and X = S,Se

The phase diagrams of the spinel systems Cd_1?xCu_xCr₂S₄, Cd_1?xCu_xCr₂Se₄, and Mn_1?xCu_xCr₂S₄ have been studied on the basis of X-ray powder photographs of quenched samples and high-temperature X-ray diffraction patterns. At room temperature the mutual solid solubilities of the metallic copper and the semiconducting cadmium and manganese spinels are only small (x < 0.05 and >0.95). The interchangeability, however, increases largely with increasing temperature. Complete series of mixed crystals, as in the Zn_1?xCu_xCr₂X₄ (X = S, Se) systems, however, are not formed. The solid solutions with x > 0.07 and <0.95, x > 0.095 and <0.90, and x > 0.36 and <0.87, respectively, formed at higher temperatures cannot be quenched to room temperature without decomposition. The unit cell dimensions of the spinel solid solutions studied obviously do not obey Vegard's rule.     

Preparation,structure, and charge transport characteristics of BIFEVOX ultrafine powders

Existence boundaries, structure, and transport parameters of ultrafine powders were studied in Bi₄V_{2 ? x} Fe _x O_{11 ? x} (BIFEVOX) solid solutions. The details of synthesis of the solid solutions via liquid precursors are analyzed comparatively. In general, BIFEVOX formation via liquid precursors is similar to phase formation in solid-phase synthesis. With low iron levels (x = 0.05–0.1), solid solutions are formed in the monoclinic α phase (space group C2/m) The compositions with x = 0.125 and 0.15 are mixtures of α- and β phases. In the range 0.2 < x < 0.7, the Bi₄V_{2 ? x} Fe _x O_{11 ? x} solid solution has the structure of the γ phase of Bi₄V₂O₁₁ (space group I4/mmm). The β phase in the system in question has a very narrow existence range in the vicinity of x = 0.175. The average particle sizes of the powders prepared by various methods are within 0.5–3 μm. In the powders prepared via liquid precursors, however, the distribution peak shifts toward smaller sizes, to 0.3–1 μm. Mechanical activation conserves the structure of the γ phase of BIFEVOX, and unit cell parameters change only insignificantly; however, the crystal lattice is slightly distorted. The electrical conductivity of BIFEVOX was studied as a function of temperature, preparation technology, and composition using impedance spectroscopy. Equivalent circuits of cells were analyzed. The conductivity of samples prepared by solution technology is always higher than for samples prepared by the solid-phase process. Features of electrical conductivity versus temperature for various phases are noted. All transitions on the conductivity curves match the features of linear thermal expansion curves. Compositions with doping levels x= 0.1–0.3 have the highest total conductivities.     

Synthesis,optical properties,and photocatalytic activity of lanthanide-doped anatase

Quasi-one-dimensional (1D) Ti_{1 ? x} Ln _x O_{2 ? x/2} anatase solid solutions were prepared by heating Ti_{1 ? x} Ln _x (OCH₂CH₂O)_{2 ? x/2} precursors, where Ln = Nd, Eu, Tb, Er (x = 0.025), or Sm (0.005 ≤ x ≤ 0.025), in air. These solid solution were found to have a photocatalytic activity in hydroquinone oxidation in aqueous solution under exposure to UV radiation. UV-Vis absorption spectra were recorded for Ti_{1 ? x} Ln _x O_{2 ? x/2} (Nd, Sm, Eu, Tb, or Er). The electronic structure and optical absorption spectra were calculated for anatase doped with neodymium, samarium, or terbium.     

Cesium-cation conduction in the systems Cs3−x P1−x E x O4 (E = S, Cr, Mo, W)

Solid solutions on the basis of cesium orthophosphate in the Cs_3?x P_1?x E _x O₄ (E = S, Cr, Mo, W) systems are synthesized. The temperature and concentration dependences of the systems’ electroconductivity are studied. The cesium-cation character of conduction in the systems is confirmed. Factors that bear upon the transport properties of the synthesized phases are analyzed.     

Electric conductivity of solid solutions in Cs2 ? 2x Fe2 ? x A x O4 systems (A = P, V)

Solid solutions based on CsFeO₂ in Cs_{2 ? 2x} Fe_{2 ? x} A _x O₄ systems (A = P, V) were synthesized. Their crystal structure and the temperature and concentration dependences of the total conductivity and its electronic component were studied. The ranges of temperature and composition in which cesium-cation conductivity was dominant were determined. The obtained data were compared with the results of studies of other cesium-conducting solid electrolytes.     

Preparation, morphology, and luminescent properties of europium-doped nanodispersed scandium sesquioxide

Scandium sesquioxide-based solid solutions of composition Sc_{2 ? 2x} Eu_2x O₃ (0.005 ?? x ?? 0.05) were prepared by thermolysis of Sc_{1 ? x} Eu _x (CH₃COO)₃ and by reacting mixtures of scandium and europium nitrates with ethylene glycol. Thermal decomposition of Sc_{1 ? x} Eu _x (CH₃COO)₃ was found to yield Sc_{2 ? 2x} Eu_2x O₃ with the shapes of aggregates atypical of the cubic structure of this oxide, and the reaction products of scandium and europium nitrates were found to have a loose spongelike structure. A spectroscopic study showed that Sc_{2 ? 2x} Eu_2x O₃ and Sc_{1 ? x} Eu _x (CH₃COO)₃ are potential luminescent materials active in the visible spectral region. The tervalent europium in the Sc_{2 ? 2x} Eu_2x O₃ structure is the source of strong red emission (⁵ D ₀ ?? ⁷ F ₂) and can be used in fluorescent lamps, colored lightning, and optoelectronic devices.     

Platinum(IV) complexation with the nitrate ion in aqueous solutions according to 195Pt, 15N, 14N, and 17O NMR data

Solutions of platinum(IV) nitrate were studied by ¹⁹⁵Pt, ¹⁵N, ¹⁴N, and ¹⁷O NMR and IR and Raman spectroscopy. It was found that in nitric acid, two interrelated systems of nitrate complexes, mono- and polynuclear ones, coexist. The complexes predominating in concentrated solutions are [Pt₂(μ-OH)(μ-NO₃)(NO₃)₂(H₂O)_{6 ? x} (OH) _x ]^{(4 ? x)+}, [Pt₄(μ-OH)₃(μ-NO₃)₃(NO₃)₃(H₂O)_{9 ? x} (OH) _x ]^{(7 ? x)+}, [Pt4(μ-OH)₄(μ-NO₃)₂(NO₃)₄(H₂O)_{8 ? x} (OH) _x ]^{(6 ? x)+}, and [Pt₄(μ-OH)₆(NO₃)₃(H₂O)_{16 ? x} (OH) _x ]^{(7 ? x)+}.     

Thermal behaviour,surface properties and vibrational spectroscopic studies of the synthesized Co3xNi3−3x(PO4)2·8H2O (0 ≤ x ≤ 1)

Co_3xNi_3−3x(PO₄)₂·8H₂O (x = 1, 0.8, 0.6, 0.4, 0.2, and 0) were synthesized via simple wet chemical reaction and energy saving route method. The final decomposition products of hydrates are corresponding anhydrous tri(cobalt nickel) diphosphates. The metal and water contents of the synthesized hydrates were confirmed by AAS and TG/DTG/DTA techniques, respectively. The observed metal and water contents agree well with the formula of the title compounds. The crystal structures and lattice parameters as well as crystallite sizes of the studied compounds were determined using XRD data. The results from XRD and TG/DTG/DTA techniques confirmed that Co_3xNi_3−3x(PO₄)₂·8H₂O at all ratios were the single phase. The FTIR spectra of studied compounds were recorded and assigned. The thermal behaviours of single and binary tri(cobalt nickel) diphosphate octahydrates were studied for the first time. The morphologies of the studied compounds were investigated by using the SEM technique. The micrographs of all studied compounds exhibited the thin plated morphology. The surface area and the pore size data of anhydrous forms were measured by N₂ adsorption at −190 °C according to the BET method. The anhydrous forms of binary metal phosphate at x = 0.8, Co_2.4Ni_0.6(PO₄)₂, exhibits the highest surface area and expects to improve the catalytic activity.     

Electron energy structure and X-ray spectra of wide-band GaN, AlN, and AlN-GaN semiconductors

The electronic energy structure of GaN, AlN, and AlGaN crystals with the wurzite structure is calculated by the local coherent potential method using the cluster version of the MT-approximation within the framework of the multiple scattering theory. The calculated densities of electron states are compared with XPS spectra of gallium and aluminum, AlL _{II, III} XES, and also with K-spectra of gallium and AlL _{II, III} XAFS absorption. The comparison of the electronic structure of Al_xGa_1?x N crystals and binary GaN and AlN and the interpretation of their features are performed. The concentration dependence of the width of the upper subband of the valence band and the band gap in Al_xGa_1?x N (x = 0, 0.25, 0.5, 0.75, 1) crystals on the content of aluminum is studied and its non-linear character shown.     

Substitutions of praseodymium and silicon for calcium and phosphorus in hydroxyapatite structure

Substituted hydroxyapatite samples of composition Ca_10?x Pr _x (PO₄)_6?x (SiO₄) _x (OH)₂, where x = 0?6, were studied using X-ray diffraction and IR spectroscopy. Calcium substitutions occurred over the entire range of compositions studied. The crystal structure of solid solutions was refined by the Rietveld technique.     

Alkali (alkaline-earth) metal,aluminum, and titanium complex orthophosphates: Synthesis and characterization

Phase formation in the A_{1 + x} Al _x Ti_{2 ? x} P₃O₁₂ (A = Li, Na, K, Rb, or Cs; 0 ≤ x ≤ 2.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} P₃O₁₂ (B = Mg, Ca, Sr, or Ba; 0 ≤ x ≤ 2.0) systems was studied using X-ray powder diffraction, electron probe microanalysis, and IR spectroscopy. The following double and triple orthophosphates were found to exist: A_{1 + x} Al _x Ti_{2 ? x} (PO₄)₃ with A = Li (0 ≤ x ≤ 0.3), Na (0 ≤ x ≤ 1.0), K (x = 0, 1.0, or 2.0), Rb (x = 0, 1.0, or 2.0), or Cs (0 ≤ x ≤ 1.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} (PO₄)₃ with B = Mg and Ba (x = 0), Ca and Sr (0 ≤ x ≤ 0.2). These orthophosphates crystallize in the structure types of kosnarite, langbeinite, cesium titanium arsenate, potassium aluminum phosphate, or rubidium aluminum phosphate. Their crystal parameters were calculated. For CsTi₂(PO₄)₃ (x = 0), Rietveld refinement was carried out: space group Ia \(\bar 3\) d, Z = 32, a = 19.909(5) Å, V = 7892(1) ų. This compound has a framework structure. The framework is built of TiO₆ octahedra and PO₄ tetrahedra; eight- and 12-coordinated Cs⁺ cations populate interstices.     

First principles calculations of electronic structure and magnetic properties of Cr-based magnetic semiconductors Al1−xCrxX (X=N, P, As, Sb)

First principles calculations based on the density functional theory (DFT) within the local spin density approximation are performed to investigate the electronic structure and magnetic properties of Cr-based zinc blende diluted magnetic semiconductors Al_1−xCr_xX (X=N, P, As, Sb) for 0≤x≤0.50.The behaviour of magnetic moment of Al_1−xCr_xX at each Cr site as well as the change in the band gap value due to spin down electrons has been studied by increasing the concentration of Cr atom and through changing X from N to Sb. Furthermore, the role of p-d hybridization is analyzed in the electronic band structure and exchange splitting of d-dominated bands. The interaction strength is stronger in Al_1−xCr_xN and becomes weaker in Al_1−xCr_xSb. The band gap due to the spin down electrons decreases with the increased concentration of Cr in Al_1−xCr_xX, and as one moves down along the isoelectronic series in the group V from N to Sb. Our calculations also verify the half-metallic ferromagnetic character in Cr doped AlX.     

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.     

Nickel deficiency in RENi2-xP2 (RE=La, Ce, Pr). Combined crystallographic and physical property studies

Large single crystals from RENi_2-xP₂ (RE=La, Ce, Pr) were synthesized from the pure elements using Sn as a metal flux, and their structures were established by X-ray crystallography. The title compounds were confirmed to crystallize in the body-centered tetragonal ThCr₂Si₂ structure type (space group I4/mmm (No. 139); Pearson's symbol tI10), but with a significant homogeneity range with respect to the transition metal. Systematic synthetic work, coupled with accurate structure refinements indicated strong correlation between the degree of Ni-deficiency and the reaction conditions. According to the temperature dependent dc magnetization measurements, LaNi_2-xP₂ (x=0.30(1)), as expected, is Pauli-like paramagnetic in the studied temperature regime, while the Ce-analog CeNi_2-xP₂ (x=0.28(1)) shows the characteristics of a mixed valent Ce³⁺/Ce⁴⁺ system with a possible Kondo temperature scale on the order of 1000 K. For three different PrNi_2-xP₂ (x?0.5) samples, the temperature and field dependence of the magnetization indicated typical local moment 4f-magnetism and a stable Pr³⁺ ground state, with subtle variations of T_C as a function of the concentration of Ni defects. Field-dependent heat capacity data for CeNi_2-xP₂ (x=0.28(1)) and PrNi_2-xP₂ (x=0.53(1)) are discussed as well.     

Synthesis,structure, ion mobility,phase transitions,and ion transport in rubidium ammonium hexafluorozirconates

Rubidium ammonium hexafluorozirconates Rb_2?x (NH₄)_x ZrF₆ (1.5 < x < 2.0) have been synthesized, and their structure, ion mobility (180–480 K), and electrophysical properties have been studied by X-ray crystallography, ¹H and ¹⁹F NMR, DTA, and impedance methods. Compounds with x > 1.5 are isostructural with (NH₄)₂ZrF₆. Rubidium cations are isomorphously substituted for the ammonium cations. The high-temperature modifications of the compounds, which form upon the phase transitions at 413–418 K, are characterized by translational diffusion of ions in the fluoride and ammonium sublattices. The ¹⁹F NMR spectra are characterized by uniaxial ¹⁹F magnetic shift anisotropy. The electrophysical properties of this series of compounds are studied in the temperature range 300–480 K.     

Phase formation in the system involving silver, magnesium, and indium molybdates

The subsolidus region of the Ag₂MoO₄-MgMoO₄-In₂(MoO₄)₃ ternary salt system has been studied by X-ray powder diffraction. The formation of new compounds Ag_{1 ? x} Mg_{1 ? x} In_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.6) and AgMg₃In(MoO₄)₅ has been established. The unit cell parameters of solid-solution samples have been determined. The Ag_{1 ? x} Mg_{1 ? x} In_{1 + x} (MoO₄)₃ phase of variable composition has a NASICON-type structure (space group R $ \bar 3 $ c) AgMg₃In(MoO₄)₅ is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P $ \bar 1 $ , Z = 2) with the following unit cell parameters: a = 7.0374(5) Å, b = 17.932(1) Å, c = 6.9822(4) Å, α = 87.309(6)°, β = 100.832(6)°, γ = 92.358(6)°. The compounds Ag_{1 ? x} Mg_{1 ? x} In_{1 + x} (MoO₄)₃ and AgMg3In(MoO₄)₅ are thermally stable up to 960 and 1030°C, respectively.