V. I. Kosyakov

Homologous series of layered tetradymite-like compounds in the Sb-Te and GeTe-Sb2Te3 systems

AbstractThe structures of layered compounds in thenSb2 ·mSb2Te3 andnGeTe ·mSb2Te3 homologous series were studied by x-ray diffraction. GeSb6Te10 (n = 1,m = 3) was shown to have a 51-layer structure (sp. gr.

600°C Section of the Fe–FeS–NiS–Ni Phase Diagram

R\bar 3m

Zonal structure of directionally solidified Fe-Ni-Cu-S materials

) withc = 10.202(1) nm. In the structure of GeSb6Te10, Sb2Te3 five-layer slabs and GeSb2Te4 sevenlayer slabs are stacked along thec axis in the ordered sequence -557 557 557-. Crystallographic data for this compound are presented. The specific and common structural features of the layered compounds in thenSb2 ·mSb2Te3 andnGeTe ·mSb2Te3 homologous series are discussed.

Preparation of eutectics by directional solidification of quaternary melts

Ellipsometry, electron microscopy, and x-ray photoelectron spectroscopy data indicate that, during HfO2 deposition onto silicon, the native oxide reacts with the HfO2 deposit to form an amorphous intermediate layer which differs in refractive index (≃1.6) from both HfO2 (1.9–2.0) and SiO2 (1.46). Thermodynamic analysis of the Si-SiO2-HfO2-Hf system shows that Si is in equilibrium with Si/HfO2 − y only at low oxygen pressures. Starting at a certain oxygen pressure (equivalent to the formation of a native oxide layer), the equilibrium phase assemblage is Si/HfSiO4/HfO2 − y.

Topologic images of phase diagrams: 1. Determination of phase diagram topology

The 600°C section of the Fe–FeS–NiS–Ni phase diagram was studied by optical and electron microscopy techniques, x-ray diffraction, and electron probe x-ray microanalysis. The results agree with the most reliable data available in the literature. The solid-solution regions identified are those of (FezNi1 – z)3 ± δS2(high-temperature heazlewoodite structure), (FezNi1 – z)S1 + δ, (FezNi1 – z)9 + δS8(pentlandite structure), α-(Fe,Ni), and γ-(Fe,Ni). The section also contains seven two-phase and three three-phase regions. The S content of the monosulfide solid solution attains 50.8 at. % at Ni : (Ni + Fe) = 0.6 and 54.0 at. % at Ni : (Ni + Fe) = 0.2. The heazlewoodite solid solution contains up to 26 at. % Fe (at 44.3 at. % S). The highest Ni content of the pentlandite solid solution is 22.5 at. % at 47.5 at. % S and 32.0 at. % at 46.2 at. % S.

Oriented crystallization of AgGaS2 from the melt system Ag-Ga-S

Topological images of the Ge-Sb-Te phase diagram are constructed on the basis of two versions of the phase relations between the low-temperature forms of Ge1-δTe in the Ge-Te system. The images have the form of flow diagrams and graphs, with labeled nodes representing the phases existing in the system. The graph edges represent two-phase mixtures and are labeled by the numbers of the phase reactions in which these mixtures appear and disappear. The graphs help to visualize the topology of the phase diagram in a compact form and are convenient for topological characterization and identification of phase reactions at invariant points.

Directional solidification of xAg2S(1−x)Ga2S3 Melts and the proof of the non-quasi-binary character of the Ag2S-Ga2S3 join

This paper examines the relationship between the phase diagram of a multicomponent system and the formation of primary zones in a directionally solidified material. The described general trends are illustrated by experimental data on the directional solidification of a melt with the composition (at %) Fe 35.0, Ni 5.0, Cu 10.0, and S 50.0. Primary zones were identified from chemical analysis data. To identify secondary zones, the phase composition of the ingot was determined by X-ray microanalysis, microstructural analysis, and X-ray diffraction.

Critical evaluation and optimization of data on the Bi-Te-Se phase diagram and crystal structure of Bi2Te3-Bi2Se3 alloys

This paper presents a theoretical analysis of quasi-equilibrium directional solidification of a quaternary melt. We consider the variation in the composition of phases in each portion of the sample and changes in phase composition for various types of phase reactions. The results indicate that the melt trajectory during directional solidification may belong only to those phase diagram elements corresponding to the crystallization of binary, ternary, or quaternary eutectics or single-phase crystallization regions. Using the directional solidification of a melt with the composition (at %) Cu 29.37, Ni 17.72, Fe 5.91, and S 47.00, we obtained a sample consisting of zones with different phase compositions: [Niz(Fe,Cu)1 − z]S1 ± δ single-phase zone, [Niz(Fe,Cu)1 − z]S1 ± δ + Cu5 ± xFe1 ± x S4 binary eutectic mixture, and [Niz(Fe,Cu)1 − z]S1 ± δ + Cu5 ± xFe1 ± xS4 + (NizFe1 − z)S2 ternary eutectic mixture. In going from one zone to another, new phases appear and the average composition of the sample changes sharply, whereas the compositions of the melt and solid solution present in neighboring zones vary continuously. These results are consistent with theoretical concepts.