Phase Composition of Heat-Treatment Products in the ZrO(OH)2–Y(OH)3–FeOOH System

The phase composition of the heat-treatment products in the ZrO(OH)₂–Y(OH)₃–FeOOH system is determined as a function of the precipitation procedure and calcination temperature (620–1570 K) for the compositions 0.97ZrO₂· xY₂O₃· yFe₂O₃(x+ y= 0.03; x= 0, 0.01, 0.015, 0.02, 0.03) and (1 – x– y)ZrO₂· xY₂O₃· yFe₂O₃(x= y= 0.02, 0.025, 0.03, 0.04). At a given ZrO₂: stabilizer ratio, partial substitution of Fe³⁺for Y³⁺increases the degree of ZrO₂stabilization and retards the low-temperature degradation of the material.     

Synthesis and Properties of Lithium Manganese Spinels

Li_{1 – x} Mn_{2 – y} Co _y O₄(x= 0–0.06, y= 0–0.15) spinels were prepared by solid-state reactions and sol–gel processing and were characterized by x-ray diffraction and scanning electron microscopy. The spinels offer satisfactory electrochemical performance and are potentially attractive as cathode materials for rechargeable lithium batteries.     

Manufacture, microstructure and mechanical properties of Mo–W–N nanostructured hard films

Mo_1−xW_xN_y (x = 0–0.67) hard films were fabricated on wafers of silicon and high speed steel by dc magnetron sputtering technique. The effect of tungsten concentration on the phase composition, microstructure, surface morphology, hardness, adhesion, and corrosion resistance of the films was studied by X-ray diffraction, scanning electron microscopy, nano-indentation, and scratch test. It was found that if the W concentration (x) in the film is in the range of 0–0.52, the films exhibit fcc (Mo,W)N_y single phase where larger W atoms substituted Mo atoms in fcc MoN_y. At higher x values (x > 0.52) the films exhibit a two-phase structure consisting of fcc (Mo,W)N_y and pure bcc tungsten phase. The hardness of the Mo_1−xW_xN_y films increases at first with increasing x, and then decreases after passing a maximum. The maximum hardness of 47 GPa is obtained at x = 0.37 corresponding to an adhesion strength of 60 N. The Mo–W–N coated high speed steel has a lower corrosion current density and higher corrosion potential than the bare high speed steel substrates.     

Determination of the Melt Undercooling Required for Producing Al x Ga y In1 – x – y Sb1 – z Bi z /InSb Heterostructures

Conditions for temperature-gradient epitaxial growth of Al _x Ga _y In_{1 – x – y} Sb_{1 – z} Bi _z /InSb heterostructures are examined. The factors are established which determine the initial melt undercooling required for preventing the thermal degradation of the substrate.     

Structures and properties of La1−x,Sr x CoO3−y,prepared by freeze drying

Several samples of La_1–x Sr _x CoO_3–y (x = 1, 0.8, 0.5, 0.2) were prepared by calcining freezedried, stoichiometric mixtures of nitrates at different temperatures and for different lengths of time. Selected samples were characterized by powder X-ray diffraction, conductivity measurements, Brunauer-Emmett-Teller surface area measurement, and by electrochemical cyclic voltammetry in alkaline solutions and alkaline solutions containing methanol. The structures of each composition were complex and varied with composition and preparation conditions. There is evidence for non-stoichiometry caused by oxygen anion vacancies. For La_0.5Sr_0.5CoO_3–y the electrochemical activity towards the oxidation of methanol is a maximum at the fully formed cubic perovskite. The oxidation currents at La_0.8Sr_0.2CoO_3–y and La_0.2Sr_0.8CoO_3–y go through maxima at more distorted structures.     

Incorporation of bismuth into Ba6− x R8+2/3x Ti18O54(R = Nd, Gd)

Microstructural investigations and microanalyses of a series of Ba_6–x R _8+2/3x Ti₁₈O₅₄ ceramics (R = Nd, Gd) revealed that the solid-solubility limit for the isovalent substitution of R ³⁺ by Bi³⁺ depends on the composition of the Ba_6–x R _8+2/3x Ti₁₈O₅₄ phase. For the Nd analogue the solid-solubility limit (y in Ba_6–x (Nd_1–y Bi _y )_8+2/3x Ti₁₈O₅₄) decreases with a decrease in x from y = 0.16 for x = 2.0 to y = 0.10 for x = 0.8. An even lower solid-solubility limit (y = 0.06) was found for the Ba_4.5(Gd_1–y Bi _y )₉Ti₁₈O₅₄ compound (x = 1.5). All substituted Nd compositions exhibit higher permittivities (93–99), lower temperature coefficients of permittivity (11–15 ppm/K) and higher dielectric losses (Q · f = 1300–5500 GHz) than the parent compositions. By exceeding the solid-solubility limit, abrupt changes in the microstructural and dielectric characteristics are induced.     

Dielectric and Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3–PbTiO3–Pb(Mg1/2W1/2)O3 Ceramics

Data are presented on the phase composition, crystal structure, microstructure, and dielectric and piezoelectric properties of (1 – y)[(1 – x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃]–yPb(Mg_1/2W_1/2)O₃ (x = 0.30–0.36; y = 0, 0.05, 0.10) ceramics. It is shown that the use of fine-particle magnesia as a starting reagent ensures the formation of single-phase materials. The ceramics with a rhombohedral structure are found to exhibit relaxor behavior. Increasing the content of the Pb(Mg_1/2W_1/2)O₃ perovskite leads to ordering of the domain structure of poled ceramics and increases their piezoelectric charge coefficient d ₃₁ and the width of their phase transitions.     

Extraordinary role of Ce–Ni elements on the electrical and magnetic properties of Sr–Ba M-type hexaferrites

The structural, electrical and magnetic behavior of Sr_0.5Ba_0.5−xCe_xFe_12−yNi_yO₁₉ (where x = 0.00–0.10; y = 0.00–1.00) hexaferrite nanomaterials are reported in this paper. The structural analysis indicates that the Ce–Ni doped Sr–Ba M-type hexaferrite samples synthesized by the co-precipitation method are stoichiometric, single magnetoplumbite phase with crystallite sizes in the range of 35–48 nm. The dc-electrical resistivity of the pure Sr–Ba hexaferrite is enhanced to almost 10² times by doping with Ce–Ni contents of x = 0.06; y = 0.60. The dielectric constant and dielectric loss tangent decrease to values 14 and <0.2, respectively, by increasing the frequency up to 1 MHz. Small relaxation peaks at frequencies >10⁵ Hz are observed for the samples with Ce content of x > 0.06. The values of saturation magnetization increase from 66.32 to 84.33 emu/g and remanance magnetization from 42.64 to 56.01 emu/g but coercivity decreases from 2.85 to 1.59 kOe by substitution of Ce–Ni. Sharp ferri-paramagnetic transition is observed in the samples, which is confirmed by DSC results. Ce–Ni substitution acts to reduce the electron-hopping between Fe²⁺/Fe³⁺ ions and also improves the magnetic properties. These characteristics are desirable for their possible use in microwave and chip devices.     

Superconductivity of La2−x Sr x CuO4 with high strontium concentration by sulphur doping

The effects of sulphur substitution for oxygen on the structure and properties of nonsuperconducting La_2–x Sr _x CuO₄, where x=0.26 and 0.30, have been studied. In La_2–x Sr _x CuO _4–y -S _y , the sulphur-doped samples exhibit superconducting transition at 37–39 K and a larger Meissner effect than undoped samples. It was found that the superconductivity of La_2–x Sr _x CuO_4–y S _y is apparently determined by the value of x–y and the strontium concentration region in which La_2–x Sr _x CuO₄ shows superconductivity shifts to higher strontium concentrations with sulphur doping.     

Possibilities for formation of the 110 K phase 2223 in Sb or V doped Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O materials

Superconducting oxide materials with nominal composition Bi_2–x Sb _x Sr₂Ca₂Cu₃O_y (x=0.05–0.3) and Bi_1.6Pb_0.4–x V _x Sr₂Ca₂Cu₃O_y (x=0.1 0.4) were synthesized. It was found that after prolonged synthesis, formation of the 2223 phase in the Bi-Sb-Sr-Ca-Cu-O system is possible. However, the critical temperatures of the samples are around 90 K and are lower than those of the superconducting materials from the Bi-Pb-Sr-Ca-Cu-O and Bi-Pb(Sb)-Sr-Ca-Cu-O systems. It was also found that V inhibits the formation of the phase 2223, raises the resistance of the samples and has a negative effect on theT _c and the phase composition of the Bi-Pb(V)-Sr-Ca-Cu-O materials.     

Partial substitution of Li for Cu in superconducting YBa2Cu3Oy

0.33–33% of the Cu in superconducting YBa₂Cu₃O _y has been replaced by Li (i.e.,x=0.01–1 in single-phase or nominal YBa₂Cu_3–x Li_xO_y). X-ray diffraction powder patterns remain the same as for YBn₂Cu₃O _y , with identical patterns up to about 17% substitution (i.e.,x=0.5). At higher percentages an additional phase appears. Electrical conductivity measurements indicate a small elevation ofT _c at low Li content. Starting at about 5% Li (x=0.15),T _c declines progressively and its width increases asx is raised.     

Development of phase change material for write once Blu-ray disc

Phase change materials based on addition of ceramic material (ZnS–SiO₂) into antimony–indium–tin (Sb_100−x−ySn_xIn_y) have been considered as possible candidates for high density optical data recording. Chemical compositions of the alloys have been optimized in order to develop a new high density Blu-ray Recordable Low to High optical data format. The evaluation of electrical parameters of resultant product shows that the jitter depends on the percentage of ZnS–SiO₂ and the chemical composition of the parent Sb_100−x−ySn_xIn_y phase change material.     

Electrical properties of BaSnO3 in substitution of antimony for tin and lanthanum for barium

Polycrystalline materials of BaSn_1–x Sb _x O_3– and Ba_1–y La _y SnO_3– were prepared. Substitutional solubilities of antimony for tin and lanthanum for barium, respectively, in BaSnO₃ were obtained to be x=0.18 for BaSn_1–x Sb _x O_3– and y<0.052 for Ba_1-y La _y SnO_3–. The X-ray photoemission spectroscopy measurements showed the valence of antimony and tin is mixed in our samples of BaSn_1–x Sb _x O_3–. At lower temperature, magnetic susceptibilities of BaSn_1–x Sb _x O_3– and Ba_1–y La _y SnO_3– satisfy the Curie law, indicating the existence of non-interacting localized electrons at the Sn⁴⁺ site, and forming a Sn⁴⁺+e^– state in these systems. By substitution of antimony and lanthanum in BaSnO₃, the conductive properties are semiconductor-like. To explain this conductive behaviour, three types of mechanism were taken into consideration.     

Pb and In Codeposition in the Vacuum Growth of PbTe<In> Films on Si Substrates

Pb_{1 – x} In _x melts were proposed to be used as In vapor sources, in combination with separate Pb and Te sources, in depositing PbTe films onto Si substrates by a modified hot-wall method. Under the assumption that the presence of Pb in Pb_{1 – x} In _x melts may raise the In partial pressure, the vaporization behavior of Pb_{1 – x} In _x (0.05 x 0.70) was studied between 900 and 1200 K in the reaction chamber of the deposition unit. Using electron probe x-ray microanalysis and x-ray diffraction, all the deposited films were shown to contain In. The In content of the Pb_{1 – y} In _y deposits varied in the range 0.002 <y < 0.07 and increased with increasing In concentration in the Pb_{1 – x} In _x melt and with increasing vapor source temperature. The vapor over molten Pb_{1 – x} In _x was shown to exhibit a positive deviation from ideality.     

Preparation and Properties of Pb1 – xSnxTe1 – ySeyEpilayers

Pb_{1 – x} Sn _x Te_{1 – y} Se _y layers lattice-matched with KCl and BaF₂are grown by liquid-phase epitaxy. Epilayer compositions and growth temperatures are determined at which p- and n-type materials can be obtained without doping. The composition dependences of the Hall coefficient and carrier mobility are analyzed.     

Superconductivity at 103 K in CdBa2(Ca0.7Y0.3)Cu2Oy

A cadmium analogue of the mercury system with nominal composition CdBa₂(Ca_1–xY_x)Cu₂O_y has been synthesized. Thex=0 samples contain about 12 vol.% of the 1212 phase but are not superconducting. Thex=0.3 samples are superconducting atT _on = 103 K. The EDX analysis of 18 microcrystals shows a broad cationic distribution of the different components. The observed broad superconducting transition is attributed to the variousT _c of the different microcrystals.     

Phase Composition, Electrical Conductivity, and Stability of ZrO2–Sc2O3–Cr2O3 Solid Electrolytes

The phase composition, electrical conductivity, and structural and electrical stability of ZrO₂–Sc₂O₃–Cr₂O₃ solid electrolytes prepared by solid-state reactions involving three-step firing at 1350, 1850 (vacuum), and 1300°C were studied for compositions along two lines: x(0.91ZrO₂ + 0.09Sc₂O₃)–yCr₂O₃ (I) andx(0.89ZrO₂ + 0.11Sc₂O₃)–yCr₂O₃ (II), x + y = 1, y = 0–0.04. The results indicate that the ternary solid solutions withy= 0.01–0.02 retain a cubic structure in a broad temperature range, down to room temperature. This increases the low-temperature (<600°C) conductivity of the solid electrolytes, especially in system II. In both systems, Cr₂O₃ solubility is about 3 mol %. Stability tests at 900°C for 200 h reduce the conductivity of the solid electrolytes, particularly at the lower Sc₂O₃ content and in the presence of Cr₂O₃. The reduction in conductivity is due to the decomposition of the high-temperature tetragonal phase and the formation of a tetragonal phase with a low stabilizer content.     

p–T–x Phase Equilibria in the Cd–Zn–Te System

The p–T–x–y phase equilibria in the Cd–Zn–Te system are analyzed. The p–T and T–x–yprojections of the p–T–x–y phase diagram and a T–x–y isobar (for pressures at which Cd_1–x Zn _x Te_{1 ±} solid solutions sublime congruently in terms of Te) are mapped out. The key features of the sublimation behavior of the solid solution are examined. The p–T projection is studied by static vapor pressure measurements at temperatures from 700 to 1300 K and pressures of up to 101.3 kPa. The p–T sections of the phase diagram are constructed for x = 0.05, 0.10, 0.15, 0.25, 0.50, 0.75, 0.90, and 1. The solid solution containing 35 mol % ZnTe is found to phase-separate at 473 K.     

Conversion mechanism of polyborosilazane into silicon nitride-based ceramics

The pyrolysis of polyborosilazane in anhydrous ammonia has been studied up to 1200 °C through the analysis of the gas phase and the characterization of the solid residue by elemental analyses, thermogravimetric analysis, Fourier transform-infrared analysis, X-ray photoelectron spectroscopy, X-ray diffraction and ²⁹Si cross-polarization/magic angle spinning-nuclear magnetic resonance. The pyrolysis mechanism involves four main steps: (1) below 400 °C, an evaporation of residual solvent and reaction with ammonia leading to an increase of nitrogen content; (2) from 400–600 °C, reaction with ammonia leading to an increase of nitrogen content and formation of preceramic polymer-ceramics intermediate solid with a three-dimensional network along with evolution of gaseous species; (3) from 600–800 °C, completion of loss of C-H functionalities and progress of formation of an amorphous ceramic, accompanied by evolution of CH₄ and H₂; (4) from 800–1200 °C, completion of formation of an amorphous hydrogenated Si-B-O-N solid composed of SiN_4–x O_x(x=0,1,2,3) and BN_3–y O _y (y=0, 1), along with evolution of H₂     

Structural investigation of amorphous iron-nickel-boron alloys

Accurate X-ray diffraction investigation has been made of ten amorphous alloys having the compositions (Fe_0.6Ni_0.4)_100–x B _x with x=14 to 24 and (Fe_100–y Ni _y )₈₀B₂₀ with y=30 to 70 which were obtained by rapid quenching from the melt. Using the common Fourier analysis, the radial distribution function was calculated from which the distance and its number of the near neighbour atoms were derived. The present results indicate that the atomic distribution of metallic glasses with low boron content differs slightly from that observed previously for a number of metallic glasses of transition metalmetalloid type. The compositional effect, in particular the boron concentration effect, on the structure and characteristic structural features of amorphous Fe-Ni-B alloy glasses is discussed together with the mean atomic volume and the partial atomic volume of metalloid elements using the measured density data.