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.     

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.     

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.     

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.     

Influence of Y(Gd) and Ni(Fe) on the principal structural characteristics of Al87Y5? x GdxNi8? y Fe ( x = 0?5; y = 0?4) amorphous metallic alloys

The X-ray diffraction method is used to study the short-range ordering of Al₈₇Y₅Ni₈, Al₈₇Gd₅Ni₈, Al₈₇Y₄Gd₁Ni₈, Al₈₇Y₄Gd₁Ni₄Fe₄, and Al₈₇Gd₅Ni₄Fe₄ amorphous alloys. The structural factors are obtained and the pair correlation functions are computed. The principal structural parameters are analyzed. It is shown that the investigated amorphous alloys are characterized by the topological short-range order based on the close-packed structure of aluminum and Al₃Y(Gd)-and Al₃Ni(Fe)-type chemical short-range ordering. It is discovered that the replacement of Y atoms with Gd atoms and Ni atoms with Fe atoms weakly affects the topology of the atomic distribution of the aluminum matrix and leads to changes in the character of chemical ordering. This affects the degree of short-range microhomogeneity of the short-range ordering and the dimensions of structural units. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 4, pp. 75–79, July–August, 2008.     

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.     

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.     

Electronic properties of SbxSe1?x glasses

The mechanism of incorporation of metallic antimony in amorphous and glassy samples of the Sb _x Se_1–x (0 x 0.10) system is studied by measuring the xerographic discharge characteristic, drift mobility and optical absorption. It is observed that the addition of antimony increases the DC conductivity, decreases the electron mobility, changes the xerographic parameters and decreases the optical gap of the system. The Compositional dependence of the electronic properties are related to the defect states produced due to incorporation of Sb atoms in glassy selenium matrix.     

Electrical properties and microstructure of CdxHg1 ? x ? yCrySe crystals

Crystals of the Cd _x Hg_{1 − x − y} Cr _y Se (x = 0.4, y = 0.1) quaternary solid solution have been grown by the Bridgman method, and their microstructure and electrical properties have been studied. The crystals are shown to contain various types of inclusions in the form of filaments and triangles.     

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.     

LiNi1 ? x ? yCoxMnyO2 (x = y = 0.1, 0.2, 0.33) cathode materials prepared using mechanical activation: Structure, state of ions, and electrochemical performance

We have investigated LiNi_{1 − x − y} Co _x Mn _y O₂ (x = y = 0.1, 0.2, 0.33) cathode materials synthesized from mechanically activated mixtures of lithium hydroxide and nickel cobalt manganese hydroxide. The materials have a layered structure (sp. gr. ). Their unit-cell volume and the degree of disordering in their structure decrease with decreasing nickel content. According to x-ray photoelectron spectroscopy data, the major states of the transition-metal ions in the surface layer of the materials are Ni²⁺, Co³⁺, and Mn⁴⁺. With increasing nickel content, the Ni 2p _3/2 and Co 2p _3/2 binding energies increase, attesting to changes in M-O bond covalence. The highest specific electrochemical capacity, ∼170 mA h/g, is offered by LiNi_0.6Co_0.2Mn_0.2O₂. The position of redox peaks in the differential capacity curves of the three materials depends on composition: with increasing nickel content, the peaks shift to lower voltages. Original Russian Text ? N.V. Kosova, E.T. Devyatkina, V.V. Kaichev, 2007, published in Neorganicheskie Materialy, 2007, Vol. 43, No. 2, pp. 227–235.     

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.

---

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.     

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.     

Effect of nonstoichiometry on the structure and microwave dielectric properties of Ba1 ? x(Zn1/2W1/2)O3 ? x and Ba(Zn1/2 ? yW1/2)O3 ? y/2

We have synthesized Ba_{1 − x} (Zn_1/2W_1/2)O_{3 − x} and Ba(Zn_{1/2 − y} W_1/2)O_{3 − y/2} barium tungstates with different deviations from cation stoichiometry (x = 0.01–0.05, y = 0.01–0.05), determined the phase composition of ceramics fabricated from the tungstates, and investigated their electrical properties. Even slight deviations from cation stoichiometry in Ba(Zn_1/2W_1/2)O₃ lead to the formation of the scheelite phase BaWO₄, and its content increases with heat-treatment temperature. Barium or zinc deficiency in the systems studied improves the sintering behavior of Ba(Zn_1/2W_1/2)O₃ and increases the degree of 1: 1 B-site cation ordering, which in turn ensures an increase in microwave quality factor, Q.     

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.     

Stabilization of the anatase phase of Ti1?xSnxO2 (x < 0.5) nanofibers

We experimentally investigate the stabilization of the anatase phase of Ti_1−x Sn _x O₂ (x < 0.5) nanofibers when synthesized by an electrospinning method. The as-spun nanofibers became nano-grained, polycrystalline nanofibers after calcination and the diameters of the nanofibers depend on Sn content. Stabilization of the anatase phase in Ti-rich compositions and incorporation of Sn ions were confirmed by X-ray diffraction, Raman, X-ray absorption near-edge structure, and photoluminescence (PL) spectroscopies. Results from the PL study also demonstrated the tunable nature of the optical properties, with the emission maximum shifting towards higher wavelength with increasing Sn concentration.      

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.     

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.     

Laser induced photoluminescence and morphological characterization of Cd(1?x)?yZnxMnyS nanocrystals

Doped II–VI chalcogenide semiconductor nanostructures have recently attracted a lot of attention due to the possibility of their application in various modern era devices. In the present study, Cd_(1−x)−y Zn _x Mn _y S {(0 ≤ x ≤ 0.5); (0.0001 ≤ y ≤ 0.1)} nanocrystals (NC) have been synthesized by facile wet chemical technique. Morphological and structural analyses of these synthesized quaternary NC have been done using X-ray diffraction (XRD) and transmission electron microscope (TEM) studies. Room temperature photoluminescence (PL) has been investigated using high peak power pulsed N₂-laser. Important optical parameter; excited state lifetime values have been calculated from the recorded multi-exponential decay curves. These fast and efficient nanophosphors have wide applications in opto-electronic industry as futuristic displays, lasers, nanoelectronics and nanosensors.