Potassium ion conducting K2 ? 2 x Fe2 ? x P x O4 solid electrolytes

Potassium ion conducting solid electrolytes based on potassium monoferrite have been prepared by substituting pentavalent phosphorus cations for Fe³⁺. The highest conductivity of K_{2 − 2x} Fe_{2 − x} P _x O₄ is achieved in the range x = 0.05−0.10: 7.1 × 10⁻³ S/cm at 300°C and 1.6 × 10⁻¹ S/cm at 700°C. The rise in the conductivity of KFeO₂ upon phosphorus doping is due to the formation of potassium vacancies. Original Russian Text ? E.I. Burmakin, G.Sh. Shekhtman, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 8, pp. 995–998.     

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.     

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.     

Structural and luminescent property of gallium chalcogenides GaSe1? x S x layer compounds

Structural and luminescence properties of GaSe_1−x S _x (0 ≤ x ≤ 1) series optical materials have been studied by X-ray diffraction, photoluminescence (PL), and piezoreflectance (PzR) measurements. Powder X-ray diffraction patterns showed the whole series layers present three different kinds of stacking formula with respect to the compositional change of sulfur from x = 0 to x = 1. The comparison of PL and PzR spectra reveals that the GaSe_1−x S _x layers have three different kinds of stacking phase from x = 0 to x = 1. The PL results show the whole series GaSe_1−x S _x layers emit the luminescences from red to blue visible region. The PL and PzR spectra of the GaSe_1−x S _x are analyzed. The structural variation in between the layers is discussed.     

Electrical properties of p -Si1 ? x Ge x Au-Based p - i - n structures and Schottky barriers

We have studied the properties of Si_{1 − x} Ge _x -based p-i-n structures and Schottky barriers in which the i-region had been produced via compensation with gold. The results demonstrate that the use of a guard ring in p-Si_{1 − x} Ge _x 〈Au〉 structures reduces the room-temperature reverse leakage current by two to three orders of magnitude. Such structures have sufficiently small reverse currents and a barrier on the order of 0.75 eV. p-Si_{1 − x} Ge _x 〈Au〉-based guard-ring structures are suitable for the fabrication of IR and nuclear detectors. Original Russian Text ? I.G. Atabaev, N.A. Matchanov, E.N. Bakhranov, M.U. Khazhiev, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 7, pp. 775–780.     

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.     

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.     

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.     

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.     

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.     

Microscopic Scenario for x = 1/8 Anomaly in La2 ? xSrxCuO4

We adopt a t ₁-t ₂-t ₃-J-G model for explanation of x = 1/8 anomaly in La_{2 – x} Sr _x CuO₄ family compound. The calculated charge susceptibility shows a maximum near Q = (, ) at intermediate temperatures and near (, /2) as temperature approaches zero, in agreement with neutron scattering experiments. Coulomb repulsion G between the first neighbors turns out to be the source of Charge Density Waves (CDW) in narrow band t ^eff ₁, t ^eff ₂, t ^eff ₃ < G. For physically realistic hopping values we obtain the CDW amplitude e _Q = x. The in-phase domain structure as a candidate for stripe picture is proposed.     

The effect of Sm substitution on properties of Bi1.6Pb0.4Sr2Ca2? x Sm x Cu3O y superconductors

The effect of the partial substitution of Ca by Sm in the Bi-2223 superconducting samples have been investigated in terms of X-ray diffraction (XRD), EDXRF (Energy Dispersive X-ray Fluorescent), magnetoresistivity, critical temperature, transport critical current density, and ac susceptibility measurements. The samples were prepared by the conventional solid-state reaction method. XRD patterns are used to calculate lattice parameters and phase ratio of the Bi-2223 samples. The volume fraction was determined from the intensities of Bi-2223 and Bi-2212 peaks. The room temperature XRD patterns of the samples showed the presence of Bi-2223 phase decreases with increasing the Sm content. We estimated the transition temperature of the samples from the resistivity versus temperature measurements in dc magnetic fields up to 0.6 T. We observed that transition temperature, T _c , and transport critical current density, , depend on the Sm substitution. They both decrease with increasing the Sm substitution. We extracted the peak temperature, T _p , and the pinning force density from our previous ac susceptibility measurements. The pinning force density decreased with increasing the Sm content. The possible reasons for the observed decreases in critical temperature and critical current density due to Sm substitution were discussed.     

Effect of heat treatment in sulfur and mercury vapors on the magnetic susceptibility of Hg1 ? x Mn x Te1 ? y S y crystals

We have studied the effect of heat treatment in mercury and sulfur vapors on the magnetic susceptibility of Hg_{1 − x} Mn _x Te_{1 − y} S _y crystals. Measurements were performed by the Faraday method in the temperature range 77–300 K at H= 318 kA/m before and after heat treatments. The results demonstrate that the behavior of the magnetic susceptibility can be understood in terms of Mn-S-Mn-S, Mn-Te-Mn-Te, and (mixed) Mn-Te-Mn-S clusters of different sizes with indirect antiferromagnetic exchange interaction between the Mn atoms through the chalcogen atoms. Heat treatment in sulfur and mercury vapors leads to the formation of new clusters or changes (increases or decreases) the size of already existing clusters. Original Russian Text ? P.D. Maryanchuk, E.V. Maistruk, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 5, pp. 549–554.     

Effects of Ga content on thermoelectric properties of P-type Ba8Ga16+ x Zn3Ge27? x type-I clathrates

P-type Ba₈Ga_16+x Zn₃Ge_27−x (x = 0.1, 0.2, 0.3, and 0.4) type-I clathrates were synthesized by combining solid-state reaction with spark plasma sintering (SPS) technology. The effects of slight increase of Ga content on thermoelectric properties have been investigated. The results show that at room temperature the carrier concentration N _p of p-type Ba₈Ga_16+x Zn₃Ge_27−x clathrates increases remarkably compared with that of Ba₈Ga₁₆Zn₃Ge₂₇ compound, which results in the increases of electrical conductivity although carrier mobility μ _H slightly decreases. The thermal conductivity κ of all samples increases with the increase of Ga content. Ba₈Ga_16.2Zn₃Ge_26.8 compound exhibits the highest ZT value of 0.43 at 700 K, which is increased by 13% compared with that of Ba₈Ga₁₆Zn₃Ge₂₇ compound.     

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.     

The morphotropic phase boundary and electrical properties of (1?? x )Pb(Zn1/2W1/2)O3– x Pb(Zr0.5Ti0.5)O3 ceramics

Ceramics in the solid solution of (1 − x)Pb(Zn_1/2W_1/2)O₃–xPb(Zr_0.5Ti_0.5)O₃ system, with x = 0.80, 0.85, 0.90, and 0.95, were synthesized with the solid-state reaction technique. The perovskite phase formation in the sintered ceramics was analyzed with X-ray diffraction. It shows that the rhombohedral and the tetragonal phases coexist in the ceramic with x = 0.90, indicating the morphotropic phase boundary (MPB) within this pseudo-binary system. Dielectric and ferroelectric properties measurements indicate that the transition temperature decreases while the remanent polarization increases with the addition of Pb(Zn_1/2W_1/2)O₃. In the composition of x = 0.85 which is close to the MPB in the rhombohedral side, a high piezoelectric property with d ₃₃ = 222 pC/N was observed.     

Dielectric, ferromagnetic and ferroelectric properties of the (1 ? x)Ba0.8Sr0.2TiO3–xCoFe2O4 multiferroic particulate ceramic composites

The (1 − x)Ba_0.8Sr_0.2TiO₃–xCoFe₂O₄ ceramic composites (x = 0–1) were prepared by standard solid state reaction method. X-ray diffraction and SEM indicate the Ba_0.8Sr_0.2TiO₃ (BST) phase and CoFe₂O₄ (CFO) phase coexist in the composites. The dielectric constant and dielectric loss for the composites were studied as a function of frequency (40 Hz–1 MHz) and temperature (30–600 °C). Magnetic and ferroelectric tests show that the ceramic composites display ferromagnetic and ferroelectric properties simultaneously. The saturated polarization of the composites decrease with ferrite concentration increasing, while the remnant polarization of the composites increase with increasing ferrite concentration. The enhanced ferroelectricity of composites may be attributed to space charge contribution in the composites.     

Structural and electrical properties of fritless Ni(1?x)CuxMn2O4 (0?≤?x?≤?1) thick film NTC ceramic

Spinel structured NTC thermistor Ni_(1−x)Cu _x Mn₂O₄ (0 ≤ x ≤ 1) ceramics was prepared by oxalic precursor method and fritless thick films screen printed on alumina. The composition dependent structural and electrical properties are reported in this paper. The results show that with increasing copper ion substitution both Cu²⁺ and Mn⁴⁺ predominantly occupy the octahedral site. The concentration of Cu²⁺ ions in octahedral site increases while that of Ni²⁺ ions decreases linearly. The thick film Ni_(1−x)Cu _x Mn₂O₄ ceramic comply with Arrhenius equation. A thermistor constant of ~1,200 K has been obtained for fritless thick film NTC ceramics using inorganic binders in the RT/90 thermal range.     

Structure of Sr1 ? xPbxFeO3 ? δ (0 < x < 0.5) perovskite-like materials

We have synthesized Sr_{1 − x} Pb _x FeO_{3 − δ} (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) perovskite-like materials and studied their structure by X-ray diffraction, M?ssbauer spectroscopy, and electron microscopy. According to the X-ray diffraction data, the Pb solubility limit in the perovskite structure is x ≈ 0.15. The materials with x = 0.05 and 0.1 contained Pb_1.33Sr_0.67Fe₂O₅ inclusions 10–30 nm in size. Using chronopotentiometry and temperature-programmed desorption, we have estimated oxygen mobility in the materials with x = 0.05 and 0.1. The results demonstrate that Pb doping increases oxygen mobility in the strontium-ferrite-based materials.     

(2?x)MgO · x(MnO, FeO) · 2Al2O3 · 5SiO2 (x = 0–2) ceramic materials and heat effects of their formation

We have determined the main characteristics of ceramic materials prepared by modifying 2MgO · 2Al₂O₃ · 5SiO₂ with MnO and FeO. The formation of the ceramics was analyzed by detailed thermal analysis, X-ray diffraction, IR spectroscopy, and differential scanning calorimetry. We have determined the heat effects of formation of Mg_{1 − x} M _x Al₂O₄ (0.25 < x < 0.75) and Mg_{2 − y} M _y Al₄Si₅O₁₈ (0.5 < y < 1.5) solid solutions with M = Mn(II) and Fe(II) and calculated the standard heats of formation of the Mg_{1 − x} M _x Al₂O₄ and Mg_{2 − y} M _y Al₄Si₅O₁₈ solid solutions.