Isothermal section of the Pt–Sb–Te system at 1000 °C

The phase relations in the system Pt–Sb–Te have been investigated at 1000 °C, using sealed glass capsule techniques. The reaction products have been studied by reflected light microscopy, X-ray diffraction, and electron probe microanalysis. At 1000 °C, Pt, PtSb, PtSb₂, Pt₃Te₄, and PtTe₂ are the stable solid phases. There are two liquid phase fields: a large field extends across the ternary system from the Pt–Sb join to the Pt–Te join, the other as a thin strip near the Sb–Te join. PtSb becomes Pt-poor up to 3 at.% from stoichiometry as substitution of Te for Sb and Pt increases. PtSb₂ and PtTe₂ exhibit the largest solid solution range among the solid phases present.     

Transition metal- chalcogen systems XI: the platinum- selenium phase diagram

The platinum-selenium phase diagram was investigated by differential thermal analysis, metallography, and X-ray powder diffraction methods. The two previously known intermediate phases, Pt₅Se₄ and PtSe₂, both melt congruently: Pt₅Se₄ at ∼1070 °C and PtSe₂ (under its own vapor pressure) at 1245 ± 10 °C. Pt₅Se₄ forms a eutectic with Pt at 1065 ± 2 °C and ∼42 at % Se and another one with PtSe₂ at 1067 ± 2 °C and somewhat below 45 at.% Se. On cooling, Pt and PtSe₂ form a metastable eutectic at 1037 ± 2 °C and ∼43 at % Se. Between PtSe₂ and Se, a degenerate eutectic was found at 221 °C, which also indicates negligible solubility of platinum in solid selenium.     

The Hafnium-Platinum Phase Diagram

Phase relationships were determined in the Hf-Pt system at temperatures up to 1690 °C using both metallographic and neutron Rietveld refinement techniques. An unusual displacive transformation is observed below 200 °C in the rhombohedral compound Hf₃Pt₄, similar to that recently discovered in the compound Zr₃Pt₄. Crystallographic data are presented for the compounds HfPt₄, HfPt₃, Hf₂Pt₃, Hf₃Pt₄, HfPt, and Hf₂Pt. A complete phase diagram is presented for the Hf-Pt binary system.     

Laves phases in the ternary systems Ti–{Pd,Pt}–Al

Formation and crystal structure of Laves phases in the systems Ti–{Pd,Pt}–Al were investigated employing XPD (X-ray powder diffraction), XSCD (X-ray single crystal diffraction) and EPMA (electron probe microanalysis) techniques. Laves phases with MgZn₂ type (space group: P6₃/mmc) and its variant with the Nb(Ir,Al)₂-type (a√3 × a√3 × c supercell of MgZn₂-type, space group: P6₃/mcm) were found in both systems. Formation of a particular structure type is dependent on temperature and composition. Laves phases with the Nb(Ir,Al)₂-type form around 25 at.% of Pd,Pt at 950 °C. The MgZn₂-type Laves phase Ti(Pt,Al)₂ was not observed at 950 °C, but it forms in as-cast alloys at a slightly lower Pt content, Ti_37.8Pt_19.0Al_43.2. In the Ti–Pd–Al system at 950 °C the MgZn₂-type phase exists at the Pd-poor side of the homogeneity region whilst the Nb(Ir,Al)₂-type phase is slightly richer in Pd. Phase relations associated with the Ti–Pt–Al Laves phase were established at 950 °C and reveal a new compound TiPtAl that derives from hexagonal ZrBeSi-type (ordered Ni₂In-type, a = 0.43925(4) nm, c = 0.54844(5); space group P6₃/mmc; R_F2 = 0.015 from single crystal data). Atom distribution in the compound shows a slight deviation from full atom order Ti(Pt_0.97Al_0.03)(Al_0.98Pt_0.02).     

Experimental thermodynamic study of intermetallic phases in the binary Ag–Te system by an improved EMF method

A thermodynamic study of the solid two-phase regions of the binary Ag–Te system was made by an improved EMF method, using fast ion conductor RbAg₄I₅ as the solid electrolyte. The EMF measurements were made on three galvanic cells: [Ag | RbAg₄I₅ | Ag₅Te₃ + Te], [Ag | RbAg₄I₅ | Ag₅Te₃ + Ag_1.9Te] and [Ag | RbAg₄I₅ | Ag_1.9Te + Ag₂Te].Based on the results obtained, the EMF for each equilibrium phase assembly was expressed as a function of temperature, in the different regions of thermal stability of the substances. By using the observed EMF and temperature relations, the thermodynamic functions of the stoichiometric equilibrium phase assemblages: Ag₅Te₃–Te, Ag₅Te₃–Ag_1.9Te, Ag₅Te₃–Ag₂Te and Ag₂Te–Ag_1.9Te, in the low-temperature range 22–204 °C, as well as phase transformation temperatures, have been determined. Agreement between the results obtained and the literature values were established.     

Experimental Investigation of the Phase Equilibria in the Co–V–Sn Ternary System

The phase equilibria of the Co–V–Sn ternary system at the 900 and 1000 °C sections were investigated experimentally by means of electron probe microanalysis and x-ray diffraction analysis. Seven three-phase regions were found in the isothermal section at 900 °C and six triphase regions at 1000 °C. The Heusler-type ternary compound Co₂VSn was confirmed at 900 °C in the composition ranges of 36.7–57.6 at.% Co and 11.8–20.9 at.% Sn, becoming slightly wider at the higher temperature of 1000 °C. Sn dissolves in α(Co), Co₃V, and σ-Co₂V₃ phases with low solubility. V is almost insoluble in liquid, with solubility of less than 0.5 at.%. The solubility of Co in V₃Sn phase increased with temperature, from 4.4 at.% at 900 °C to 11.6 at.% at 1000 °C.     

Precipitation Behavior of Pt2Mo-Type Superlattices in Hastelloy C-2000 Superalloy with Low Mo/Cr Ratio

This paper focuses on the precipitation behavior of superlattices phases in new Hastelloy C-2000 alloy with low Mo/Cr ratio owing to their detrimental effects on both mechanical and corrosion-resistance properties of the alloys. The precipitation behavior of superlattices phases in the C-2000 alloy was investigated at 600 °C in the aging time range of 100-500 h. The results revealed that Pt₂Mo-type superlattices phases have been precipitated after aging at 600 °C for 100 h. Typically, the Pt₂Mo-type precipitated phases meet to a stoichiometric ratio of Ni₂(Cr, Mo) in this alloy. As increasing aging time from 100 to 500 h, size of the phase increases from around 13 to 55 nm. Besides, morphology of the Ni₂(Cr, Mo) precipitated phases changes from a lean to a fat ellipse with increasing aging time due to the effect of the Mo/Cr atomic ratio and alloying elements on transformation paths from disorder to order. In addition, solution temperature of the Pt₂Mo-type superlattices is around 725 °C determined by differential scanning calorimetry method, which was significantly dependent on the heating rate.     

An investigation of the Pt-Al-Ru diagram to facilitate alloy development

The platinum-rich region of the Pt-Al-Ru system was investigated with a view to stabilizing the displacive (martensite-type) transformation in Pt₃Al. In the alloys with low ruthenium contents, ruthenium was found to be partitioned almost exclusively to the fcc Pt phase with extremely limited solubility in Pt₃Al. The low-temperature D0′_C form of Pt₃Al was found to co-exist with the Pt phase. At high Ru additions (greater than 20 at.%), a two-phase mixture of an hcp Ru solid solution and the high-temperature L1₂ form of Pt₃Al was observed. No ternary phases were observed in any of the alloys studied.     

An investigation of the Pt-Al-Ru diagram to facilitate alloy development

The platinum-rich region of the Pt-Al-Ru system was investigated with a view to stabilizing the displacive (martensite-type) transformation in Pt₃Al. In the alloys with low ruthenium contents, ruthenium was found to be partitioned almost exclusively to the fcc Pt phase with extremely limited solubility in Pt₃Al. The low-temperature D0′_C form of Pt₃Al was found to co-exist with the Pt phase. At high Ru additions (greater than 20 at.%), a two-phase mixture of an hcp Ru solid solution and the high-temperature L1₂ form of Pt₃Al was observed. No ternary phases were observed in any of the alloys studied.     

Phase Equilibria at 1173 K in the Ternary Fe-Pt-Tb System

The solid-state phase equilibria in the ternary Fe-Pt-Tb system in the compositional region below 75 at.%Tb at 1173 K have been studied by using x-ray diffraction, scanning electron microscopy and energy dispersion spectroscopy techniques. The 1173 K isothermal section consists of 18 single-phase regions, 33 two-phase regions, and 16 three-phase regions. At 1173 K, the maximum solid solubility of Pt in α-(Fe, Tb) is less than 2 at.%Pt and that of Pt in Fe₂Tb, Fe₃Tb, Fe₂₃Tb₆, Fe₁₇Tb₂ is below 1 at.%Pt; the compounds Pt₅Tb, Pt₃Tb, Pt₂Tb, Pt₄Tb₃, PtTb, Pt₄Tb₅, Pt₃Tb₅, PtTb₂, and PtTb₃ are confirmed to exist at 1173 K and the highest solid solubility of Fe in them is below 1 at.% Fe; the maximum solid solubility of Tb in α-(Fe, Pt), γ-(Fe, Pt), FePt, FePt₃, and (Pt, Fe) (namely, the solid solution of Fe in Pt) is about 1, 2, 1.9, 1.5, and 1.5 at.%Tb, respectively. No ternary compound was found to exist in this section at 1173 K.     

The Fe-A1-Ti system

An extensive experimental investigation of the Fe-Al-Ti system by metallography, microprobe analysis, and XRD on quenched specimens and on diffusion couples is presented. Two isothermal sections at 800 and 1000 °C were established; they differ substantially from the existing (800 °C) or partly determined (1000 °C) diagrams. From these results, existence of the τ₁ phase (Fe₂AlTi) can be ruled out. Existence of the ternary compounds, τ₂ (Al₂FeTi) and τ₃ (Al₂₂Fe₃Ti₈), is confirmed. The composition limits of both phases were determined; they differ considerably from those given in earlier reports. The τ₂ phase apparently exists in a cubic and a tetragonal polymorph, depending on composition. The cubic form exists at high titanium contents. At 1000 °C, the two polymorphs are separated by a miscibility gap. At compositions where the “X phase” (Al₆₉Fe₂₅Ti₆) was previously reported, single-phase samples were obtained at both temperatures. From the present results, there is no evidence to assume that this is a new ternary phase rather than the ternary homogeneity range of the Al₃Fe phase. In addition, extensions of the binary intermetallic phases into the ternary system were determined.     

Synthesis and characterization of new amorphous and crystalline phases in Bi2O3–SrO–TeO2 system

Tellurite glasses containing strontium and bismuth oxides have been prepared at 800 °C and investigated by X-ray diffraction, differential scanning calorimetry and infrared. The crystalline phases of glasses in TeO₂–SrO revealed γTeO₂ phase which transforms into the stable αTeO₂ phase up to 500 °C. Infrared study shows the transition of TeO₄, TeO₃₊₁ and TeO₃ units with increasing SrO content. The value of refractive index and density of glasses have been measured. The investigation in the system by the solid-state reaction technique using XRD reveals a new phase Bi₂Te₆SrO₁₆.     

Properties of nickel-cobalt composite silicides by thermal annealing of Ni<Subscript>1−x</Subscript>Co<Subscript>x</Subscript> (x=0.2, 0.5, and 0.8) alloy thin films on silicon and polysilicon substrates

10 nm-Ni_1−xCo_x (x=0.2, 0.5, and 0.8)/p-Si(100)(or poly crystalline Si) was thermally annealed using rapid thermal annealing for 40 s at 600–1100°C. The annealed film structures developed into NiCoSi_x, and the resulting changes in sheet resistance, microstructure, and composition were investigated using a four-point probe, a scanning electron microscope, a field ion beam, an X-ray diffractometer, and an Auger electron spectroscope. The final thickness of NiCoSi_x formed on single-crystal silicon was approximately 12.64nm, and it maintained its sheet resistance below 20 Ω/sq. during the silicidation annealing at 1100°C. The NiCoSi_x formed on polysilicon had a thickness of 35.04nm, and its low resistance was maintained up to 900°C. Additional annealing of silicides at the given RTA temperature for 30 min resulted in a drastic increase in sheet resistance. We identified Ni₃Si₂ and a NiSi phase at 700°C and 1000°C for single-crystal silicon substrates. Moreover, Ni₃Si₂, NiSi, and CoSi₂ phases were stable at 700°C, and then NiSi₂ and Ni₃Si₂ became stable for polycrystalline silicon substrates at 1000°C. When the amount of Co was 80%, only a Ni₃Si₂ phase was confirmed at 700°C and 1000°C in both the single and polycrystalline substrates. With less Co (Co=0.2, 0.5), Ni₃Si₂, NiSi, and CoSi₂ phases were observed at 700, and Ni₃Si₂ and NiSi₂ phases were observed at 1000°C. Cobalt also improved thermal stability of the silicides formed on the polysilicon gate, but this enhancement was lessened due to the silicon mixing during high temperature diffusion. In conclusion, the proposed nickel cobalt composite silicides formed from the nano-thick alloy films may be superior to conventional nickel monosilicides due to improved thermal stability.     

Thermoelectric properties of the 0.05 wt.% SbI3-Doped n-Type Bi2(Te0. 95Se0. 05)3 alloy fabricated by the hot pressing method

Thermoelectric properties of the 0.05 wt.% SbI₃-doped n-type Bi₂(Te_o.95Se_o.o5)₃ alloy, fabricated by hot pressing at temperatures ranging from 350°C to 550°C, were characterized. The electron concentration of the alloy decreased as the hot pressing temperature increased due to the annealing-out of the excess Te vacancies. When hot pressed at 350°C, a figure-of-merit of 0.75x10^-3/K was obtained due to the low Seebeck coefficient of -145 μV/K and relatively high electrical resistivity of 2.05 mΩ-cm. Upon increasing the hot pressing temperature, however, the figure-of-merit was improved mainly due to the increase of the Seebeck coefficient. A maximum figure-of-merit of 2.1x10^-3/K was obtained by hot pressing at 550°C.     

Aluminising of steel with a cathodic arc plasma based method

Steel samples have been aluminised by cathodic arc PVD using Al cathodes and AC bias. The effect of time and temperature on the growth behaviour of iron aluminide phases under the constant flux of Al vapour was investigated. For samples processed at 1000°C for 30?min a layered structure that consisted of FeAl, followed by dual phase regions of metastable Fe₃Al?+?FeAl and stable Fe₃Al?+?α-Fe was observed. Increase of processing time resulted in the formation of Fe₂Al₅. The increase of processing temperature to 1100°C extended the diffusion zone and increased the time for formation of Fe₂Al₅. After 90?min processing at 1000°C and 1100°C the presence of Fe₄Al₁₃ in the Fe₂Al₅ phase was determined. It has been observed that the metastable dual phase structures composed of Fe₃Al and FeAl can be transformed into stable Fe₃Al by heat treatment at 500°C.     

Thermodynamic assessment of the Ga–Pt system

The Ga–Pt binary system has been thermodynamically assessed by means of the computer program Thermo-Calc. The Redlich-Kister polynomial was used to describe the solution phases, liquid (L) and fcc (Pt). The compounds, Ga₆Pt, Ga₇Pt₃, Ga₂Pt, Ga₃Pt₂, GaPt, Ga₃Pt₅ and GaPt₂, were treated as stoichiometric phases. The sublattice-compound energy model was employed to describe the compound GaPt₃, with a homogeneity range. The parameters of the Gibbs energy expressions were optimized according to all the available experimental information of both the equilibrium data and the thermodynamic results. A set of self-consistent thermodynamic parameters of the Ga–Pt system has been obtained. The calculations agree well with the respective experimental data.     

Experimental Investigation of Phase Equilibria in the Fe-Nb-Ta System

The phase equilibria in the Fe-Nb-Ta ternary system at 1200, 1100 and 1000 °C were experimentally investigated. The microstructure of each sample was observed using scanning electron microscopy, and phase compositions were measured by energy dispersive spectrometry. The constituent phases of typical samples were analyzed with x-ray diffraction. The experimental results indicated that the continuous solid solution phases, Fe₂(Nb,Ta) and Fe₇(Nb,Ta)₆, were formed between Fe₂Nb and Fe₂Ta and Fe₇Nb₆ and Fe₇Ta₆, respectively, and no ternary compounds were found in this system in these isothermal sections. Based on the experimental phase equilibria data obtained in the present work, three isothermal sections at 1200, 1100 and 1000 °C were constructed.     

The Fe-A1-Ti system

An extensive experimental investigation of the Fe-Al-Ti system by metallography, microprobe analysis, and XRD on quenched specimens and on diffusion couples is presented. Two isothermal sections at 800 and 1000 °C were established; they differ substantially from the existing (800 °C) or partly determined (1000 °C) diagrams. From these results, existence of the τ₁ phase (Fe₂AlTi) can be ruled out. Existence of the ternary compounds, τ₂ (Al₂FeTi) and τ₃ (Al₂₂Fe₃Ti₈), is confirmed. The composition limits of both phases were determined; they differ considerably from those given in earlier reports. The τ₂ phase apparently exists in a cubic and a tetragonal polymorph, depending on composition. The cubic form exists at high titanium contents. At 1000 °C, the two polymorphs are separated by a miscibility gap. At compositions where the “X phase” (Al₆₉Fe₂₅Ti₆) was previously reported, single-phase samples were obtained at both temperatures. From the present results, there is no evidence to assume that this is a new ternary phase rather than the ternary homogeneity range of the Al₃Fe phase. In addition, extensions of the binary intermetallic phases into the ternary system were determined.     

Experimental Determination of Phase Equilibria in the Co-Cr-Ni System

The phase equilibria between the γ (A1) and liquid phases and those between the γ, ε (A3), σ (D8_b) and α (A2) phases at temperatures between 750 and 1300 °C in the Co-Cr-Ni system were determined by differential scanning calorimetry and electron probe microanalysis. It was found that the γ solidus and liquidus temperatures decrease with increasing Cr or Ni content and that the difference between them increases with increasing Cr content. The phase equilibria at 800, 900, 1000, 1100, 1200 and 1300 °C were determined using two- or three-phase alloys, and the phase boundaries due to the magnetically induced phase separation in the γ and ε phases were also observed at 850, 800 and 750 °C by the diffusion couple method.     

Optical response characteristics arising from delocalized electrons in phase change materials

Phase change materials have great potential for data storage applications owing to the large optical and electrical contrasts during rapid switching between their amorphous and crystalline phases. Hence, significant efforts have been made to identify and understand their unique characteristics. Here, we report a distinct optical characteristic of phase change materials and explain its presence via electronic structure considerations. The optical response of phase change materials and non-phase change materials are investigated via experiments. Annealing them from room temperature to 400 °C, we observed that Sb₂Te₃ exhibits phase change properties but not Bi₂Te₃, despite their similar crystal structures. A red shift in the absorption spectra is observed for crystalline Sb₂Te₃ with respect to its amorphous phase. From first-principles calculations, we explain that the delocalized electrons in crystalline Sb₂Te₃ films are responsible for this red shift. In contrast, the electrons in Bi₂Te₃ films are localized and no absorption red shift is observed. The absorption red shift is also observed in other phase change materials from the GeTe–Sb₂Te₃ pseudo-binary system; hence the detection of such a red shift may be used for identifying potential phase change materials.