Rubidium ion conducting Rb2 ? 2xAl2 ? xAxO4 (A = Nb, Ta) solid electrolytes

Rb_{2 − 2x} Al_{2 − x} A _x O₄ (A = Nb, Ta) solid solutions have been synthesized, and their conductivity has been measured as a function of temperature and composition. The highest rubidium ion conductivity in the Rb_{2 − 2x} Al_{2 − x} A _x O₄ solid solutions is 3.16 × 10⁻³ S/cm at 300°C and ∼ 2 × 10⁻² S/cm at 700°C. The high rubidium ion conductivity of the synthesized solid electrolytes is mainly due to the formation of rubidium vacancies when Nb⁵⁺ or Ta⁵⁺ substitutes for Al³⁺ and to the specific features of the crystal structure of RbAlO₂.     

Oxygen-ion diffusion and electrical conduction of La2Mo2?2 x Fe x O9?δ systems

Based on the novel oxygen ion conductor La₂Mo₂O₉, a series of Fe-doped samples of La₂Mo_2−x Fe _x O_9−δ (x = 0, 0.025, 0.05, 0.1) was prepared by conventional solid-state reaction method. The structure, phase transition, oxygen ion diffusion and electrical conductivity were studied with X-ray diffraction (XRD), differential scanning calorimeter (DSC), direct current (dc) resistivity, and dielectric relaxation (DR) measurements. One DR peak associated with the short-distance diffusion of oxygen vacancies was observed in both temperature and frequency spectra. The activation energy for oxygen ion diffusion in Fe-doped La₂Mo₂O₉ samples was smaller than that in un-doped samples. Fe doping can increase the ionic conductivity of La₂Mo_2−x Fe _x O_9−δ samples as well as the ionic transference number in the temperature range from 680°C to 400°C in comparison with the un-doped samples, although the electronic conductivity slightly increases. It is found that because of the small solubility of Fe₂O₃ in La₂Mo₂O₉ (<5%), Fe doping cannot suppress the phase transition that occurred around 570°C, but 2.5% K doping at La site at the same time (e.g. in sample La_1.95K_0.05Mo_1.95Fe_0.05O_9−δ ) can completely suppress this phase transition and increase conductivity at lower temperatures.     

Melt synthesis of oxide phosphors with K2NiF4 structures: CaLa1? x Eu x GaO4

In order to synthesize compounds of various Perovskite-related structures, we have utilized a novel “melt synthesis technique” for phosphors rather than the conventional solid state reaction techniques. The solid state reactions require multi-step processes of heating/cooling with intermediate grindings to make homogeneous samples. However, for the melt synthesis, it is possible to make a homogeneous sample in a single step within a short period of time (1–60 s) due to the liquid phase reaction in the molten samples, which were melted by strong light radiation in an imaging furnace. In this study, we have prepared a red-phosphor CaLaGaO₄:Eu³⁺ which has a perovskite—related layered K₂NiF₄ structure. Well-crystallized CaLa_1−x Eu _x GaO₄ samples with the K₂NiF₄ structure have been obtained up to x = 0.25, but there was the formation of an olivine phase when x = 0.5–1.0. The red emission at 618 nm increased with the increasing value of x up to x = 0.25.

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Synthesis and properties of Ca1 ? xTiSi1 ? xFe2xO5 solid solutions

We have studied the CaTiSiO₅-Fe₂TiO₅ system. Ca_{1 − x} TiSi_{1 − x} Fe_2x O₅ solid solutions were prepared by low-temperature plasma synthesis in a hydrogen-oxygen flame. The CaTiSiO₅-Fe₂TiO₅ system contains two phases of variable composition: α (monoclinic structure) and β (orthorhombic structure). We have determined the homogeneity ranges, unit-cell parameters, and electrical parameters of the synthesized solid solutions. The Ca and Si in CaTiSiO₅ can be replaced by Fe³⁺. Fe³⁺ substitution increases the conductivity of the material by up to five orders of magnitude.     

Electronic structure and chemical bonds in the magnetic semiconductors Mn x Cd1 ? x GeAs2 and Mn x Zn1 ? x GeAs2

The electronic structure of the magnetic semiconductors Mn _x Cd_{1 − x} GeAs₂ and Mn _x Zn_{1 − x} GeAs₂, where x = 0, 0.0625, and 0.125, is calculated by the method of electron density functional in the plane-wave basis. Features of participation of Mn3d-electrons in the chemical bond are revealed. It is found that their role in the chemical bond with group-V element depends on the group-II element and the concentration of the magnetic dopant. Original Russian Text ? V.G. Yarzhemskii, S.V. Murashov, V.I. Nefedov, E.N. Muraviev, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, no. 11, pp. 1300–1306.     

Ionic conductivity of mixed phosphates of the composition Li3 ? 2 x Nb x In2 ? x (PO4)3

The properties of Li_{3 − 2x} Nb _x In_{2 − x} (PO₄)₃ phosphates have been studied by impedance spectroscopy, x-ray diffraction, and electron microscopy. The effect of heterovalent substitution on the thermal expansion and lattice parameters of the phosphates has been examined. Their electrical conductivity is shown to rise in going from Li_0.6Nb_1.2In_0.8(PO₄)₃ to LiNbIn (PO₄)₃ and from Li_1.2Nb_0.9In_1.1(PO₄)₃ to Li₃In₂(PO₄)₃, which can be accounted for by consecutive filling of the M(1) and M(2) sites in the structure of the phosphates. Original Russian Text ? A.R. Shaikhlislamova, A.B. Yaroslavtsev, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 11, pp. 1361–1366.     

Electrical conductivity and thermal stability of (1 ? x )CsH2PO4/ x SiP y O z ( x = 0.2–0.7) composites

The physicochemical properties of (1 − x)CsH₂PO₄/xSiP _y O _z (x = 0.2–0.7) composites containing fine-particle silicon phosphates as heterogeneous additives have been studied at different humidities. The introduction of silicon phosphates suppresses the superionic phase transition of CsH₂PO₄ and increases the low-temperature conductivity of the materials, which depends significantly on humidity. The CsH₂PO₄-SiP _y O _z materials offer high conductivity (∼3 × 10⁻³ to 10⁻² S/cm at ∼110–230°C) at low water vapor pressures (3 mol % H₂O). Amorphization of the CsH₂PO₄ in the composites markedly changes its thermodynamic properties. The effect of long-term isothermal holding (210°C, 3 mol % H₂O) on the conductivity of the composites has been studied. Original Russian Text ? V.G. Ponomareva, E.S. Shutova, G.V. Lavrova, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 9, pp. 1131–1136.     

Elastic and inelastic properties of (Co0.45Fe0.45Zr0.1) x (Al2O3)1 ? x nanocomposites

The elastic (Young’s modulus) and inelastic (internal friction) properties of amorphous (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 − x} nanocomposites with various relative contents of the metallic and dielectric phases have been studied. In the region of low temperatures, the composites exhibit a peak of the internal friction (at ∼240 K), the intensity of which increases with the content of the metallic phase. For compositions above the percolation threshold, the temperature dependence of the internal friction exhibits exponential growth above 300°C, which is related to the migration of vacancy-like defects in the amorphous structure of the metallic phase.     

Dielectric properties of (1 ? x)KNbO3 · xBiZn2/3Nb1/3O3 (x ≤ 0.4) perovskite solid solutions

(1 − x)KNbO₃ · xBiZn_2/3Nb_1/3O₃ ceramic materials have been prepared by solid-state reactions. The materials with x < 0.5 have been shown to be phase-pure perovskite solid solutions. Their average lattice parameter increases linearly with x. Below 300 K, the solid solutions with 0.1 < x ≤ 0.4 are ferroelectric relaxors. M″-M′ diagrams, representing the relationship between the real and imaginary parts of the complex electric modulus, have been used to evaluate the Curie temperature of the solid solutions and the temperature of their transition to the paraelectric phase. The Arrhenius plots of dc conductivity for the solid solutions show breaks corresponding to their phase transitions. Below 400 K, the dc conductivity is low, and its contribution to the dielectric response of the solid solutions is insignificant. Original Russian Text ? I.I. Moroz, N.M. Olekhnovich, Yu.V. Radyush, A.V. Pushkarev, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 6, pp. 747–753.     

Electrical conductivity of LaCoxFe1 ? xO3 ? δ and LaLi0.1CoxFe0.9 ? xO3 ? δ (0 ≤ x ≤ 0.4) oxides

We have studied the effect of Co and Li concentrations on the phase composition and electrical conductivity of LaCo _x Fe_{1 − x} O_{3 − δ} and LaLi_0.1Co _x Fe_{0.9 − x} O_{3 − δ} perovskite-like oxides synthesized in air at 1470 K. Single-phase materials with an orthorhombic crystal structure were obtained in the range 0 ≤ x ≤ 0.3. The composition dependences of conductivity have a minimum at x _c = 0.1 and 0.2, respectively. In the range x > 0.1, the conductivity of LaCo _x Fe_{1 − x} O_{3 − δ} increases with increasing Co concentration for T > 700 K and decreases for T < 600 K. The conductivity of La(Li_0.1Co _x Fe_{0.9 − x} )O_{3 − δ} in the range 0 ≤ x ≤ 0.1 and for x ≥ 0.2 increases with Co concentration throughout the temperature range studied.     

Dielectric and piezoelectric properties of (1 ? 2x)BiScO3 · xPbTiO3 · xPbMg1/3Nb2/3O3 (0.30 ≤ x ≤0.46) solid solutions

We have synthesized ceramic samples of (1 − 2x)BiScO₃ · xPbTiO₃ · xPbMg_1/3Nb_2/3O₃ perovskite solid solutions with 0.30 ≤ x ≤ 0.46 and studied their structural, dielectric, and piezoelectric properties. At x = 0.40, the system has a morphotropic phase boundary between tetragonal (x > 0.40) and rhombohedral (x < 0.40) solid solutions. The dielectric permittivity and loss tangent of the solid solutions have been measured at temperatures from 100 to 800 K and frequencies from 0.1 to 200 kHz. The maximum in the permittivity of the solid solutions lies in the range 390–440 K. With increasing BiScO₃ content, features characteristic of fer-roelectric relaxors emerge and become more pronounced. Near the morphotropic phase boundary, the piezoelectric charge coefficients d ₃₃ and d ₃₁ of the solid solutions reach 410 and 150 pC/N, respectively, and their radial-mode mechanical Q drops to 22, which makes these materials potential candidates for a number of applications.     

AgCl x Br1 ? x and AgCl x Br y I1 ? x ? y crystals for IR engineering and optical fiber cables

The AgCl-AgBr phase diagram was refined, and TlI-doped AgCl _x Br _y I_{1 − x − y} crystals are grown. AgCl _x Br _y I_{1 − x − y} crystals were characterized by physicochemical methods. Two types of single-mode IR cables were manufactured for operation at 10.6 μm, and their fundamental characteristics were calculated: the difference between the refractive indices of the core and cladding, core diameter, numerical aperture, and critical angle of internal reflection at the normalized frequency parameter V = 2.0. Original Russian Text ? L.V. Zhukova, N.V. Primerov, A.S. Korsakov, A.I. Chazov, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 12, pp. 1516–1521.     

Phase composition and structure of La1 ? x Ca x MnO3 + δ (0 ≤ x ≤ 0.2) solid solutions

A structural phase diagram of La_{1 − x} Ca _x MnO_{3 + δ} (0 ≤ x ≤ 0.2) solid solution in air has been constructed for the first time, and the equilibrium T-x fields of the monoclinic, orthorhombic, and rhombohedral phases in this system have been outlined. The transitions between these phases are accompanied by sharp changes in lattice parameters, suggesting that they are first-order. Original Russian Text ? S.Kh. Estemirova, A.M. Yankin, S.G. Titova, V.F. Balakirev, Yu.E. Turkhan, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 11, pp. 1387–1392.     

Electrical properties of (K0.5Na0.5)1? x Ag x NbO3 lead-free piezoelectric ceramics

(K_0.5Na_0.5)_1−x Ag _x NbO₃ lead-free piezoelectric ceramics have been fabricated by an ordinary ceramic technique. The results of XRD reveal that Ag⁺ diffuses into the K_0.5Na_0.5NbO₃ lattices to form a new solid solution with an orthorhombic perovskite structure and the solubility of Ag⁺ into A-sites of K_0.5Na_0.5NbO₃ is about 0.20. The ceramics can be well-sintered at 1,100–1,110 °C. The partial substitution of Ag⁺ for A-site ion (K_0.5Na_0.5)⁺ decreases slightly both paraelectric cubic-ferroelectric tetragonal (T _C) and ferroelectric tetragonal-ferroelectric orthorhombic phase transition temperatures (T _O−T). The ferroelectricity of the ceramics becomes weak at high Ag⁺ concentration. The ceramic with x = 0.10 possesses optimum electrical properties: d ₃₃ = 135 pC/N, k _P = 0.43, k _t = 0.46, ε _r = 470, tanδ = 3.39%, and T _C = 394 °C.     

Structural and dielectric spectroscopy studies of the M-type barium strontium hexaferrite alloys (Ba x Sr1? x Fe12O19)

The M-type barium hexaferrite Ba _x Sr_1−x Fe₁₂O₁₉ (where 0 < x < 1) alloys were prepared by a new ceramic procedure. The samples were studied using X-ray diffraction and Rietveld analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, infrared and M?ssbauer spectroscopy. The X-ray analysis indicates that the all the samples present a hexagonal structure. The IR spectra showed three main absorption bands in range of 400–600 cm⁻¹ corresponding to SFO100 and BFO100. The M?ssbauer spectra showed a superposition of five subspectra associated with the five sites of the iron ion, which in the ferric state. The SEM studies showed that the hexaferrites presented grains that varied in the range of 260–305 nm. The dielectric properties: dielectric constant (ε′) and dielectric loss (tg δ) were measured at room temperature in the frequency range from 100 Hz to 40 MHz. The samples present a nonlinear behavior for the dielectric constant at 100 Hz, 1 kHz and 1 MHz. The dielectric constant is not following the linear mixing rule for the samples. The structural, dielectric and magnetic properties of the composite barium hexaferrite phases were discussed in view of applications as a material for permanent magnets, high density magnetic recording and microwave devices.     

Electronic Properties and Superconductivity of Electron-Doped La1?x/2Pr1?x/2CexCuO4

La_1−x/2Pr_1−x/2Ce _x CuO _y (LPCCO) samples with doping level up to 20% have been synthesized and their electronic and superconductive properties are studied. X-ray diffraction revealed that the LPCCO system is a pure phase system with a T’214 structure. Magnetic and resistive measurements show that the system is superconducting at 0.08≤x<0.20 with T _cmax=25 K at x=0.12. An anti-ferromagnetism transition was also observed in under-doped PLCCO (x=0.05) with the window width of the anti-ferromagnetism phase being significantly narrower than that NCCO and PCCO systems. The behavior of the Ce doping is compared with Sr doping in this system, and the mechanism is discussed.     

Effect of Zn2TiO4 and ZnB2O4 additions on the microstructure and dielectric properties of AgNb1 ? xTaxO3 solid solutions

We report the preparation and characterization of AgNb_0.6Ta_0.4O₃ (ANT) based materials. The addition of Zn₂TiO₄ and ZnB₂O₄ influences the sintering temperature, phase composition, and microstructure of ANT ceramics. ANT doped with 1 wt % Zn₂TiO₄ or ZnB₂O₄ has high dielectric permittivity (400–470), low dielectric losses (tanδ ∼ 10⁻³), and a nonlinearity coefficient n _R ≅ 3–9% (at a field strength E = 3 × 10⁶ V/m).     

X-ray diffraction study of multicomponent oxides in the Zn2 ? x(TiaZrb)1 ? xFe2xO4 system

The multicomponent refractory oxide system Zn_{2 − x} (Ti _a Zr _b )_{1 − x} Fe_2x O₄ (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 2: 1, 3: 1, 4: 1; x = 0–1.0; Δx = 0.05) has been studied by X-ray diffraction, using samples prepared by melting appropriate metal oxide mixtures in a low-temperature hydrogen-oxygen plasma. Two phases, both with wide homogeneity ranges, have been identified: α-phase, with a cubic inverse spinel structure, and β-phase, with a tetragonal inverse spinel structure. The phase boundaries in the system have been determined. Structural data are presented for about 100 solid solutions.     

La3+ effect on dipole ordering in Pb1 ? xLax[Zr0.7Sn0.2Ti0.1][1 ? x/4]O3(0 < x ≤ 0.03) solid solutions

We have studied temperature- and electric-field-induced phase transitions in ceramic samples of Pb_{1 − x} La _x [Zr_0.7Sn_0.2Ti_0.1]_{1 − x /4}O₃ (0 < x ≤ 0.03) solid solutions. The results indicate that La³⁺ doping to x > 0.005 impedes long-range dipole-dipole interactions and stabilizes nonpolar phases below the Curie temperature. At a constant La³⁺ concentration, lowering the temperature facilitates a field-induced transition to a ferroelectric state. In thermally depoled samples, the first antiferroelectric → ferroelectric switching usually requires a higher bias voltage than do subsequent switchings. Original Russian Text ? E.A. Bikyashev, E.A. Reshetnikova, M.I. Tostunov, 2009, published in Neorganicheskie Materialy, 2009, Vol. 45, No. 8, pp. 990–995.