Electrical properties of Ba2(In1 − x Al x )2O5 solid solutions

The electric conductivity of perovskite-like Ba₂(In_{1 ? x} Al _x )₂O₅ solid solutions (0 < x ≤ 0.20) characterized by structural disordering in the oxygen sublattice was studied as a function of temperature and partial pressure of oxygen in an atmosphere with a low content of water vapors ( $p_{H_2 O}$ = 3 × 10^?5 atm). When In³⁺ was partially replaced by Al³⁺, the oxygen ion conductivity increased because of the disordering of oxygen structural vacancies, leading to a significant increase in the total electric conductivity of the samples.     

Magnetic properties of (Cu0.5Ga0.5)1 − x Fe x Cr2S4 solid solutions

Magnetic properties are studied and a magnetic phase diagram is constructed for (Cu_0.5Ga_0.5)_{1 ? x} Fe _x Cr₂S₄ solid solutions formed between chromium chalcogenide spinels (Cu_0.5Ga_0.5)Cr₂S₄ and FeCr₂S₄.     

Electrochemical properties of solid solutions in the Li8Zr1 − x Ce x O6 system

Li₈Zr_{1 ? x} Ce _x O₆ solid solutions based on lithium zirconate Li₈ZrO₆ were obtained by solid-state synthesis in an inert atmosphere. Their transport properties (the electron component of the total conductivity, the temperature and concentration dependences of conductivity, and the activation energies) were studied by impedance spectroscopy. The practical stability of the ceramic samples of Li₈Zr_{1 ? x} Ce _x O₆ solid solutions (x = 0–0.07) at 473–573 K against melted lithium was studied.     

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.     

Characterization of superparamagnetic Mg x Zn1−x Fe2O4 powders

Structural and magnetic properties of Mg _x Zn_1−x Fe₂O₄ powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg _x Zn_1−x Fe₂O₄ (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones.      

Magnetic properties of Cu0.5Fe0.5 ? x Ga x Cr2S4 solid solutions

Solid solutions between ferrimagnet Cu_0.5Fe_0.5Cr₂S₄ (T _C = 347 K) and antiferromagnet Cu_0.5Ga_0.5Cr₂S₄ (T _N = 31 K) have been synthesized, and their magnetic properties studied. Both compounds belong to the A _0.5 ⁺ A _0.5 ³⁺ Cr₂X₄ group with the 1 : 1 order of A⁺ and A³⁺ ions in the tetrahedral spinel sites. Measurements on a SQUID magnetometer over wide ranges of fields (0.05?C40 kOe) and temperatures (5?C300 K) provided a deeper insight into the nature of magnetism and cation distribution in the studied samples.     

Sol-gel formation and properties of nanocrystals of solid solutions Y1 − x Ca x FeO3

Nanopowders of ferrites Y_{1 ? x} Ca _x FeO₃ (x = 0.1, 0.2, and 0.3) were prepared by chemical coprecipitation of cations Y³⁺, Ca²⁺, and Fe³⁺ by an aqueous sodium carbonate solution. It was found that an increase in the calcium content leads to a decrease in the size of nanocrystals, the average size of which is 25–50 nm. Doping of yttrium orthoferrite with the doubly charged calcium ion enhances magnetization and decreases coercivity in samples.     

Synthesis and study of the properties of the solid solutions K2Y1−x Tb(Tm) x (MoO4)(PO4) and K2Y1−x Tm x (MoO4)(PO4)0.95(VO4)0.05

The solid solutions K₂Y_1?x Tb(Tm) _x (MoO₄)(PO₄) and K₂Y_1?x Tm _x (MoO₄)(PO₄)_0.95(VO₄)_0.05 were synthesized, which are isostructural and crystallize in the orthorhombic crystal system (space group Ibca). The luminescence intensity of the terbium-containing samples increases with increase in the terbium content. The thulium-containing samples are characterized by intense luminescence in the blue spectral region and concentration quenching of luminescence. The introduction of the vanadate anion adversely affects the luminescence intensity.     

Thermodynamic properties of the Zr0.8Ti0.2(MnxCr1−x)FeH2 system

The effects of the substitution of chromium by manganese in Zr_0.8Ti_0.2(Mn_xCr_1−x)Fe Laves phase alloys on the pressure-composition-isotherm (PCT) relations, especially on the plateau slopes and hysteresis, were systematically investigated by PCT measurements. There is no dependence of the hydrogen storage capacity on composition as manganese is substituted for chromium. Increasing manganese substitution increases the extent of hysteresis but decreases the degree of the plateau slopes as well as the hydride stability. This is caused by the more sensitive change in the equilibrium pressures for hydride formation than for hydride decomposition in the two-phase region as the alloy composition x varies. It is suggested from the above results that the compositional dependence of the PCT relations of the Zr_0.8Ti_0.2(Mn_xCr_1−x)FeH₂ system originates from the difference in nature of the hysteresis behavior between ZrMn₂-type and ZrCr₂-type Laves phase alloy systems, since the hysteresis energies show a drastic change around x = 0.5. The difference in hysteresis nature is probably related to the difference in mechanical properties of the alloy itself, i.e. between ZrCr₂-type and ZrMn₂-type Laves phases.     

Synthesis and characterization of substitutional solid solutions aLn2O3 · (1 − a)Bi2O3 · 4TiO2

The solubility of 10 lanthanide elements and of scandium is solid Bi₂Ti₄O₁₁ has been determined using Raman spectroscopy and X-ray diffraction. The data obtained were used to construct a diagram of solubility as a function of the ionic radii of bismuth and the lanthanide elements. The thermal stability of the solid solutions as a function of temperature and duration of thermal treatment has been qualitatively established.     

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.     

Synthesis and magnetic properties of Cu0.5Fe0.5 ? x In x Cr2S4 (x = 0?0.4) solid solutions

Multistep synthesis with X-ray diffraction monitoring of the phase composition has been carried out, optimal synthesis parameters have been determined, and the magnetic properties of solid solutions between thiospinels with ordered tetrahedral A lattices (ferrimagnet Cu_0.5Fe_0.5Cr₂S₄ (T _C = 347 K) and anti-ferromagnet Cu_0.5In_0.5Cr₂S₄ (T _N = 35 K) have been studied. Both compounds crystallize in F $\bar 4$ 3m (T _d ² ) structure. Measurements over wide ranges of fields (0.05?C40 kOe) and temperatures (5?C300 K) highlighted the nature of magnetism in the samples; new magnetic species have been discovered.     

Magnetic and high rate adsorption properties of porous Mn(1-x)Zn(x)Fe2O4 (0 ≤ x ≤ 0.8) adsorbents

Porous spinel ferrites Mn(1-x)Zn(x)Fe(2)O(4) (0 ≤ x ≤ 0.8) are synthesized by a simple sol-gel method with egg white. All samples exhibit porous morphologies and large BET surface area (S(BET)). The substitution of Zn(2+) affects the magnetic properties of ferrites and the adsorption properties of methylene blue (MB) on ferrites, obviously. The saturation magnetization (Ms) of Mn(1-x)Zn(x)Fe(2)O(4) increases before x=0.4, and decreases with further increase of Zn(2+) substitution. This can be ascribed to the changes of the cationic distribution and the variation of spin arrangement in A-site and B-site of spinel structure. All samples show high adsorption capacity and the removal efficiencies of MB reach up to >90% within 3 h. The Zn(2+) substitution accelerates the adsorption rate and capacity of MB on Mn(1-x)Zn(x)Fe(2)O(4). The quickest adsorption occurred at x=0.2 and the largest adsorption capacity occurred at x=0.8.     

The structures of the solid solutions formed in the system (CrxFe1−x)VO4

Solid solutions (Cr_xFe_1−x)VO₄ can be prepared over a wide composition range and are thermally stable to above 900°C. They are isomorphous with α-MnMoO₄ rather than adopting the CrVO₄ or FeVO₄ structures. At 3000 atm pressure, a reversible transformation to a CrVO₄ type polymorph takes place. substitution of small amounts of phosphate into CrVO₄ also produces an α-MnMoO₄ isomorph.     

Thermodynamic properties of solid solutions of silica in forsterite (Mg2Si1+γO4+2γ)

From solid state electrochemical measurements on Mg₂SiO₄SiO₂ solid solutions in air at 1300 K ≤ T ≤ 1780 K the thermodynamic (excess) functions are calculated. A pronounced nonideality is found.     

Pyrochlore solid solutions (LaxY1−x)2Mo2O7, x = 0.0 to 0.5. Spin-glass-like behavior

The (La_xY_1−x)₂Mo₂O₇ system was investigated in the range x = 0.0 to x = 0.5. Single-phase materials exist up to x = 0.4; the x = 0.5 composition has a small impurity contamination. The lattice constants are linear with x and range from 10.224 Å (x = 0.0) to 10.461 Å (x = 0.5). These lattice constants span the same range as the R₂Mo₂O₇ series from R = Y to R = Nd. In this series, there is a discontinuous change from ferromagnetic long-range order to short-range spin-glass-like order between R = Gd and R = Tb. Yet, the solid solutions all show spin-glass-like properties with maxima in the susceptibility in the 20–25 K range and sample-history-dependent effects at lower temperatures. Deviations from the Curie-Weiss Law occur well above the susceptibility maxima. The Weiss constants change from −61 to +41 K for x = 0.0 and x = 0.5, respectively, indicating a competition between antiferromagnetic and ferromagnetic exchange interactions. This competition, coupled with the inherent frustration of the Mo⁴⁺ lattice in space group Fd3m is a possible origin of the spin-glass properties.     

Electrochemical study of spinel oxide systems with nominal compositions Ni1− x Cu x Co2O4 and NiCo2− y Cu y O4

Studies on the electrochemical behaviour of Ni_{1− x} Cu _x Co₂O₄ (x ≤ 0.75) and NiCo_{2− y} Cu _y O₄ (y ≤ 0.30) electrodes in 5 mol dm⁻³ KOH aqueous solutions are presented. The oxide layers have been prepared by thermal decomposition of aqueous nitrate solutions on nickel supports at 623 K. Powder samples were also prepared by thermal decomposition under the same conditions. The powder samples and the oxide layers were characterised by X-ray powder diffraction. The influence of the copper content on the voltammetric response of the electrodes and activity towards oxygen evolution reaction is analysed and correlated with the surface composition of the electrodes by means of X-ray photoelectron spectroscopy data. The analysis of the results reveals that the presence of Cu affects the electrode behaviour and its influence depends on which cation has been replaced. Received: 22 February 1999 / Accepted: 26 October 1999     

Mechanical properties of mixed conducting La0.5Sr0.5Fe1−x Co x O3−δ (0≤x≤1) materials

Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of and , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials. Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending was in the range 107–128 MPa. The corresponding fracture toughness of , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m^1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient temperature fracture strength and toughness.