Calorimetric studies of non-isothermal crystallization in amorphous Cu x Ti100−x alloys

The present paper reports the composition dependence of pre-exponential factor and activation energy of non-isothermal crystallization in amorphous alloys of Cu _x Ti_100?x system using differential scanning calorimeter (DSC) technique. The applicability of Meyer-Neldel relation between the pre-exponential factor and activation energy of non-isothermal crystallization for amorphous alloys of Cu-Ti system was verified.     

Mössbauer spectroscopic studies of the crystallization of amorphous Fe80B20−x Si x (x=0, 2, and 8) alloys

The crystallization process of amorphous Fe₈₀B_20–x Si _x (x=0, 2, and 8) ferromagnetic alloys has been studied by using ⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction studies. Results for samples heat treated at different temperatures for different times show that the crystallization of Fe₈₀B_20–x Si _x samples having x=0 and 2 leads to -Fe and t-Fe₃B, while for x=8, it leads to -Fe, t-Fe₂B, and perhaps Fe-Si. It is further observed that the addition of silicon to the Fe-B system improves the thermal stability of the system.     

Effect of illumination on the crystallization kinetics of amorphous Se80−xTe20Inx

The present paper reports the effect of illumination on the crystallization kinetics in amorphous Se_80–xTe₂₀In_x (0x10). The crystallization was monitored by measuring the electrical conductivity of isothermally annealed samples held at temperatures near the crystallization temperature. It is observed that the crystallization becomes faster in the presence of light as compared to a pure thermal case. There is no significant change in the activation energy under illuminated conditions as compared to the purely thermal case.     

Precipitation of (PdxAg1−x)3 In in Ag-25% Pd-In alloys and the partial phase diagram of ternary Ag-Pd-In alloys

A study was carried out to determine the partial phase diagram for the system Ag-25 wt % Pd–y wt% In with y 8 by X-ray powder diffraction and differential thermal analysis. The liquidus and solidus temperatures decreased with increasing indium content up to 8 wt % In for a given 25 wt % Pd. The solvus curve of phase identified as Pd_xAg_1-x)₃ In was determined by the parametric method and the temperature dependence of In-solubility in Ag-25 wt % Pd was very strong above 900 °C. ©2000 Kluwer Academic Publishers     

Formation and properties of amorphous (Fe1−x Nb x ) l B100−l

Amorphous (Fe_1–x Nb _{x l} B_100–l alloys with 0 x 0.15 and 74 T _g, crystallization temperatureT _x, and microhardnessH _v, but to decrease the magnetization and Curie temperatureT _c. The effects of niobium onT _x,H _v, andT _c in iron-based amorphous alloys are similar to those of chromium, manganese, molybdenum, tungsten and vanadium.     

The morphology of α-Fe crystals which grow in the amorphous Fe80(C1−xBx)20 alloys

Crystallization behaviour of amorphous Fe₈₀(C_1–x B _x )₂₀ alloys, obtained by splat-cooling technique, for x values ranging from zero to unity has been investigated mainly by transmission electron microscopy. The crystalline phase which first appeared in the amorphous matrix was -Fe for all alloys studied. However, the morphology of -Fe phase changed from a spherical shape for low x values to a watch-glass shape for intermediate x values and to dendritic for large x values. The nucleation of -Fe crystals was homogeneous for low x samples while preferred nucleation on edges and surfaces was noted for samples with higher x values. The final volume fraction of -Fe phase before the appearance of the second crystalline phase increased with the increase in x.     

Decomposition of (Sn2xFe1−xSb1−x)O4 solid solutions with x≤0.50

Thermal stabilities of the rutile-type (Sn_2xFe_1−xSb_1−x)O₄ solid solutions with x≤0.5 were investigated by TG–DTA in flowing O₂ up to 1673 K. After thermal analysis the samples were characterised by means of powder X-ray diffraction analysis (XRD), optical and scanning electron microscopy (SEM) observation and electron dispersive spectrometry (EDS) analysis. The decomposition of the solid solution involves the formation of hematite and a volatile Sb oxide, probably Sb₄O₆. The decomposition temperature increases with the Sn content of the solid solution.     

Crystallization kinetics of bulk amorphous (Se65Te35)100−x Sb x

Kinetic studies of crystallization in (Se₆₅Te₃₅)_100–x Sb _x with 0x10 glasses, using the differential scanning calorimetry technique, were performed. Crystallization enthalpy data, H _c, were collected as a function of composition. The crystallization data were examined in terms of recent analyses developed for non-isothermal crystallization studies, to arrive at E _c. The results indicate bulk nucleation and crystallization with two- and three-dimensional growth, respectively, for the (Se₆₅Te₃₅)₉₈Sb₂ and (Se₆₅Te₃₅)₉₂Sb₈ glass composition.     

Crystallization kinetics of Zr-rich FexZr0−x0−x0−x(20 ⩽ x ⩽ 40) metallic glasses

The crystallization kinetics of the melt-spun Fe-Zr metallic glasses in the iron-rich region has been investigated by means of DSC and X-ray diffraction. The crystallization mode changes with iron concentration. In the lower iron region, 20 x 25, the Fe _x Zr100–x glasses crystallize into -Zr and Ti₂Ni-type FeZr₂ with an accompanying sharp and large exotherm at the first crystallization step and immediately after this step, they transform into orthorhombic FeZr₃. On the other hand, the alloys with 35 x 40 exhibit a gradual exotherm which initiates from a temperature far below the definite crystallization temperature (T _x). The Fe-Zr metallic glasses in this concentration region crystallize polymorphously into the oxygenstabilized Ti₂Ni-type FeZr₂ with accompanying relatively small and composite exotherms. The annealing at a temperature where the gradual exotherm occurs for the alloys with 30 x 40 does not cause any changes of X-ray halo pattern but results in the reduction of the heat of exotherm due to the crystallization.     

Photoconductivity in single crystals of (TlGaSe2)1−x(TlInS2)x alloys (0−0.45 ≤ x ≤0.55-1)

The spectral distribution of the photoconductivity in (TlGaSe₂)_1−x(TlInS₂)_x single crystals has been studied at 77 K and 300 K. At O ≤ x ≤ 4, Eg is observed to vary linearly with x. Eg(x) deviates from linearity at x = 0.6. This deviation is attributed to the effect of disorder in the composition. Over the range 0.6 to 2.2 eV pronounced impurity photoconductivity is detected at 77 K and 300 K. Deep impurity levels and their neighbourhood in this alloy are established to preserve their positions with the variation in the composition. The analysis of the obtained results indicates that the impurity centres are mainly connected with the cation neighbourhood.     

Optical properties of amorphous (GeS)1 − x Bi x (0 ≤ x ≤ 0.15) films and a tentative cluster model for their structure

This paper examines the effect of Bi doping on the optical properties of amorphous (GeS)_{1 ? x} Bi _x (0 ≤ x ≤ 0.15) films. Experimental data in conjunction with first-principles electronic structure calculations for Ge _n S _m and Bi _n S _m clusters are used to derive a cluster model for the structure of the amorphous (GeS)_{1 ? x} Bi _x films.     

Hydrogen sorption properties of V1 − x Cr x (x = 0.1–0.5) alloys

We have studied the interaction of hydrogen with vanadium-chromium alloys. Hydrogen absorption and desorption isotherms have been constructed, the stability ranges of the forming hydride phases have been determined, and the ΔH and ΔS of the reactions involved have been evaluated. X-ray diffraction characterization results indicate the formation of three hydride phases, with fcc, bcc, and hcp structures.     

Magnetic and Magnetocaloric Properties of Laves Phase Dy1−x Gd x (Co1−x Ni x )2 Solid Solutions

We report magnetic and magnetocaloric properties of the polycrystalline series of Dy_1?x Gd _x (Co_1?x Ni _x )₂ (x=0.1, 0.2, 0.3, 0.4 and 0.5) solid solutions. The samples were characterized by powder X-ray diffraction patterns taken at room temperature and revealed that all the Dy_1?x Gd _x (Co_1?x Ni _x )₂ solid solutions consist of the C15 cubic Laves phase MgCu₂ type structure and a small amount of DyCo₃ and Dy₂O₃ impurity phases. Magnetic measurements showed that the samples undergoes a second-order type phase transition at T _C<130 K, from paramagnetic to ferromagnetic state. Heat capacity measurements have been performed for all solid solutions and allowed us to determine the Debye temperature. The magnetocaloric effect has been studied by means of specific heat measurements in magnetic field 0.42, 1 and 2 T. The GdNi₂ substitution effect on magnetic and magnetocaloric properties will be discussed.     

Phase diagram and some properties of Cu2−xSe(2.01≥2−x≥1.75)

The temperatures of phase transformation from low-temperature -phase to high-temperature -phase were measured for copper selenide Cu_2–x Se in the composition range 2.012–x1.75. The -phase was found to be unstable in air, and further experiments should be performed in a good vacuum. The phase diagram of Cu_2–x Se was redetermined by the X-ray parametric method and the possible reasons why the phase diagrams reported by several authors do not coincide with each other are discussed.     

Magnetic characterization of Zr(Cr1−x Cu x )2 alloys and their hydrides

Magnetization measurements were carried out on the alloys Zr(Cr_1–x Cu _x )₂ (x=0, 0.1, 0.3, 0.5) before and after hydrogenation. All the binary and the ternary alloys, as well as their hydrides, exhibit a temperature-independent or nearly temperature-independent Pauli type of paramagnetism. Beside the Pauli paramagnetism, a ferromagnetic contribution to the total magnetization was observed for most of the alloys and their hydrides. It was also observed that hydrogen absorption enhances the Pauli paramagnetism as well as the ferromagnetism of the alloys. The rather unusual magnetic behaviour of these systems is briefly discussed in terms of 3d band filling of the transition metal, and is compared with some related systems.     

Growth of perfect-crystal Si-Si1−x Gex-(Ge2)1−x (InP)x structures from the liquid phase

Structures comprising Si-Si_1−x Ge_x-(Ge₂)_1−x (InP)_x with an intermediate Si_1−x Ge_x buffer layer were grown on silicon substrates. Morphological examinations, scanning patterns and diffraction spectra, and also the electrophysical and luminescence properties of the heterostructures were used to show that the crystal perfection of these structures depends on the choice of liquid-phase epitaxy conditions. Pis’ma Zh. Tekh. Fiz. 25, 37–40 (December 26, 1999)     

Eu3+ activated novel alkaline earth metal gallium oxide phosphors: Sr(2.92−x)Ca(x)Ga2O6:Eu3+0.08 for light emitting diodes

Present study deals with Eu³⁺ activated novel alkaline earth metal (Sr and Ca) gallium oxide phosphors, Sr_(2.92?x)Ca_(x)Ga₂O₆:Eu³⁺_0.08 (x = 0 to 2.92). Crystal structure, morphology and luminescence (excitation, emission and CIE coordinate) properties of these phosphors have been studied as a function of Ca concentration. Doping of Ca ions into Sr_2.92Ga₂O₆:Eu³⁺ phosphor gives rise to a significant enhancement in overall fluorescence and the optimum emission is attained for pure Ca_2.92Ga₂O₆:Eu³⁺ phosphor for x = 2.92. The intensity ratio of ⁵D₀ → ⁷F₂ to ⁵D₀ → ⁷F₁ transitions (monochromaticity) of Eu³⁺ for different doping concentration of Ca suggests that asymmetry around the Eu³⁺ ion increases with increase in Ca ion concentration, which is responsible for enhanced emission. The excellent optical features, such as broad excitation band (230–480 nm) and excellent emission in red region (at 614 nm), conclude that calcium gallet phosphor could be a potential candidate for light emitting diodes and display applications.