Phase equilibria and glass formation in the As2S3-TlAs2S2Se2 section of the As2S3-As2Se3-TlS system

Alloys in the As₂S₃-TlAs₂S₂Se₂ section of the As₂S₃-As₂Se₃-TlS ternary system were studied and a phase diagram was constructed using physicochemical methods (differential thermal analysis, microstructural analysis, X-ray powder diffraction, also microhardness and density measurements). The diagram in the As₂S₃-TlAs₂S₂Se₂ section is a non-quasi-binary diagonal section of the As₂S₃-As₂Se₃-TlSe quasi-ternary system. It was found that all the alloys in the section under ordinary conditions are obtained in the vitreous state. At low As₂S₃ concentrations in the section, solid solutions form up to 2.5 mol %, and at low TlAs₂S₂Se₂ concentrations, their extent is 3 mol %.     

Phase equilibria in the pseudo-binary system SrO-Fe2O3

The phase relations in the pseudo-binary system SrO-Fe₂O₃ have been investigated in air up to 1150°C by means of powder X-ray diffraction and thermal analysis. Sr₃Fe₂O_7−δ, SrFeO_3−δ and SrFe₁₂O₁₉ are stable phases in the entire investigated temperature region, whereas Sr₂FeO_4−δ and Sr₄Fe₃O_10−δ decompose above 930±10°C and 850±25°C, respectively. Sr₄Fe₆O_13±δ is entropy-stabilized relative to SrFeO_3−δ and SrFe₁₂O₁₉ above 775±25°C. Extended solid-solution Sr_1±xFeO_3−δ was demonstrated. On the Fe-deficient side, the extent of solid solubility appeared to decrease gradually with temperature, whereas an abrupt decrease due to formation of Sr₄Fe₆O_13±δ was observed above 775°C on the Sr-deficient side.     

Phase equilibria in the Ag2Te-PbTe-Bi2Te3 system

Phase equilibria in the Ag₂Te-PbTe-Bi₂Te₃ quasi-ternary system were studied by differential thermal analysis, X-ray powder diffraction, and measurements of microhardness and emf of concentration circuits with an Ag₄RbI₅ solid electrolyte. Some polythermal sections and isothermal (600 and 800 K) sections of the phase diagram, and also a projection of the liquidus surface were constructed. The primary crystallization fields of phases were determined, and the types and coordinates of invariant and monovariant equilibria were found. The system is characterized by the formation of a wide continuous band of high-temperature solid solutions (γ phase) with a cubic structure along the PbTe-AgBiTe₂ section. With decreasing temperature (T ≤ 715 K), AgBiTe₂ and γ solid solutions, close in composition to this compound, experience solid-phase decomposition to form Bi₂Te₃, ternary tetradymite-like phases of the PbTe-Bi₂Te₃ boundary system, and the low-temperature phase of Ag₂Te.     

Phase equilibria in the Tl2Te-SnTe-Bi2Te3 system

phase equilibria in the Tl₂Te-SnTe-Bi₂Te₃ system were studied by differential thermal analysis (DTA), X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl₅Te₃ structure (δ) and solid solutions based on SnTe (γ₁), Tl₂Te (α), Bi₂Te₃ (β), and two TlBiTe₂ (γ₂ and γ′₂) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the β-, γ₁-, γ′₂-, and δ phases and the compounds SnBi₂Te₄ and SnBi₄Te₇. The liquidus of the α phase is degenerate. The primary crystallization fields of phases were determined, and the types and coordinates of in- and monovariant equilibria were found.     

Phase diagrams of sections in the EuS-Cu2S-Nd2S3 system

Phase equilibria in the EuS-Cu₂S-Nd₂S₃ system were studied in an isothermal (970 K) section and NdCuS₂-EuS and Cu₂S-EuNdCuS₃ polythermal sections. The complex sulfide EuNdCuS₃ has an orthorhombic crystal lattice (space group Pnma; a = 1.10438(2) nm, b = 0.40660(1) nm, c = 1.14149(4) nm), is isostructural to BaLaCuS₃, and melts incongruently at 1470 K: EuNdCuS₃ (0.50 EuS; 0.50 NdCuS₂) ai 0.18 EuS ss (0.88 EuS; 0.12 NdCuS₂) + 0.82 L (0.415 EuS; 0.585 NdCuS₂); ΔH = 17.8 kJ/mol. Within the range 0.5 mol % EuS, EuNdCuS₃-based solid solutions were not found. At 970 K, the tie lines pass from the compound EuNdCuS₃ to Cu₂S, EuS, NdCuS₂, and EuNd₂S₄ phases and lie between the NdCuS₂ phase and solid solutions (ss) of γ-Nd₂S₃ with EuNd₂S₄. Eutectics are formed between the compounds NdCuS₂ and EuNdCuS₃ at 32.0 mol % EuS T = 1318 K and between the compounds Cu₂S and EuNdCuS₃ at 20.5 mol % EuNdCuS₃ and T = 1142 K. Five main subordinate triangles were identified in the system.     

Tl2S-Sb2S3-Bi2S3 quasi-ternary system

The Tl₂S-Sb₂S₃-Bi₂S₃ quasi-ternary system (system A) was studied using DTA, X- ray powder diffraction, microstructure examination, and microhardness measurements. TlSbS₂-Tl₄Bi₂S₅(TlBiS₂, Bi₂S₃), Sb₂S₃-TlBiS₂, Tl₃SbS₃-TlBiS₂(Bi₂S₃), and [TlSb_0.5Bi_0.5S₂]-Tl₂S isopleths; isothermal sections at 500 K; and liquidus surface projection of system A were constructed. Characteristic features of the title system are extensive fields of solid solutions extended along the TlSbS₂-TlBiS₂ quasi-binary section and a continuous solubility belt 1–2 mol % wide extended along the Sb₂S₃-Bi₂S₃ binary subsystem. Primary separation fields of phases and the types and coordinates of invariant and monovariant equilibria in system A were determined.     

Phase equilibrium in the PbSnS2-PbSb2S4 system

The PbSnS₂-PbSb₂S₄ system was studied by physicochemical methods, and its phase diagram was plotted. The system is quasi-binary; solid solutions regions based on PbSnS₂ (6 mol % PbSb₂S₄) and PbSb₂S₄ (12 mol % PbSnS₂) were revealed. At a component ratio of 1: 1, a congruently melting compound Pb₂SnSb₂S₆ is formed. Pb₂SnSb₂S₆ single crystals were obtained by chemical transport. The unit cell parameters of Pb₂SnSb₂S₆, which crystallizes in orthorhombic system, were determined: a = 15.22 ?, b = 10.68 ?, c = 3.90 ?.     

Vaporization chemistry and thermodynamics in the CdGa2S4-Ga2S3 system

The chemistry and thermodynamics of vaporization of CdGa₂S₄(s), CdGa₈S₁₃(s), and Ga₂S₃(s) were studied by computer-automated, simultaneous Knudsen-effusion and torsion-effusion, vapor pressure measurements in the temperature range 967–1280 K. The vaporization was incongruent with loss of Cd(g) + 1/2 S₂(g) and production of CdGa₈S₁₃(s), a previously unknown compound, in equilibrium with CdGa₂S₄(s), until the solid became CdGa₈S₁₃ only. Then, incongruent vaporization continued with production of Ga₂S₃(s) until the solid was Ga₂S₃ only. The latter vaporized congruently. The ΔH°(298 K) of combination of one mole of CdS(s) with one mole of Ga₂S₃(s) to give CdGa₂S₄(s) was ?22.6 ± 0.9 kJ mole^?1. The 2H2(298 K) of combination of one mole of CdS(s) with four moles of Ga₂S₃(s) to give CdGa₈S₁₃(s) was ?25.5 ± 1.1 kJ mole^?1. The 2H2(298K) of CdGa₈S₁₃(s) with respect to disproportionation into CdGa₂S₄(s) and 3 Ga₂S₃(s) was ?2.8 ± 0.6 kJ mole^?1. CdGa₈S₁₃(s) was not observed at room temperature. The 2H2(298 K) of vaporization of the residual Ga₂S₃(s) was 663.4 ± 0.8 kJ mole^?1, which compared well with a value of 661.4 ± 0.3 kJ mole^?1 already available from the literature. Implications of small variations in stoichiometry of compounds in this study were observed and are discussed.     

Phase equilibria in the system V2O3Ti2O3TiO2 at 1473°K

The phase equilibria in the V₂O₃Ti₂O₃TiO₂ system have been determined at 1473°K by the quench method, using both sealed tubes and controlled gaseous buffers. For the latter, $\text{CO}{}_2\text{H}{}_2$ mixtures were used to vary the oxygen fugacity between 10^?10.50 and 10^?16.73 atm. Under these conditions the equilibrium phases are: a sesquioxide solid solution between V₂O₃ and Ti₂O₃ with complete solid solubility and an upper stoichiometry limit of (V, Ti)₂O_3.02; an M₃O₅ series which has the V₃O₅ type structure between V₂TiO₅ and V_0.69Ti_2.31O₅ and the monoclinic pseudobrookite structure between V_0.42Ti_2.58O₅ and Ti₃O₅; series of Magneli phases, V₂Ti_n?2O_2n?1Ti_nO_2n?1, n = 4–8; and reduced rutile phases (V, Ti)O_2?x, where the lower limit for x is a function of the $\text{V}\text{(V + Ti)}$ ratio. The extent of the different solid solution areas and the location of the oxygen isobars have been determined.     

Crystal structures of CsFe2S3 and RbFe2S3: synthetic analogs of rasvumite KFe2S3

The isostructural alkali thioferrate compounds CsFe₂S₃, RbFe₂S₃ and KFe₂S₃ have been synthesized by reacting Fe and S with their corresponding AFeS₂ (A=K, Rb, Cs) precursors. The crystal structures of these and binary compounds of intermediate composition were determined by Rietveld analysis of laboratory powder X-ray diffraction patterns. All of the synthesized compounds adopt the space group Cmcm (#63), Z=4 with: a=9.5193(8) Å, b=11.5826(10) Å, c=5.4820(4) Å for CsFe₂S₃; a=9.2202(7) Å, b=11.2429(9) Å, c=5.4450(3) Å for RbFe₂S₃; and a=9.0415(13) Å, b=11.0298(17) Å, c=5.4177(6) Å for KFe₂S₃. These mixed valence alkali thioferrates show regular changes in cell dimensions, AS₁₀ (A=K, Rb, Cs) polyhedron volumes, polyhedron distortion parameters, and calculated oxidation state of Fe with respect to increasing size of the alkali element cation. The calculated empirical oxidation state of iron varies from +2.618 (CsFe₂S₃), through +2.666 (RbFe₂S₃) to +2.77 (KFe₂S₃).     

SnSbBiS4-SnS and SnSbBiS4-Sn2Sb6S11 sections of the SnS-Sb2S3-Bi2S3 ternary system

SnSbBiS₄-SnS and SnSbBiS₄-Sn₂Sb₆S₁₁ sections were studied by physicochemical methods (DTA, X-ray powder diffraction, microstructure observation, and microhardness measurements). These sections were found to be eutectic quasi-binary sections of the SnS-Sb₂S₃-Bi₂S₃ ternary system. Solid solution regions based on the initial components were found on either side of the sections. Alloys in the solid solution region are p-type semiconductors.     

Phase diagram of the Pb5Sb4S11-Pb2SnSb2S6 system

The Pb₅Sb₄S₁₁-Pb₂SnSb₂S₆ system was studied by a number of physicochemical methods, and its phase diagram was constructed. It was found that the system under investigation is a quasi-binary eutectic type section of the SnS-PbS-Sb₂S₃ ternary system. The coordinates of the eutectic are found to be 33 mol % Pb₅Sb₄S₁₁ and 750 K. Regions of solid solutions based on Pb₅Sb₄S₁₁ (6 mol % Pb₂SnSb₂S₆) and Pb₂SnSb₂S₆ (4 mol % Pb₅Sb₄S₁₁) were determined.     

Phase diagram of the In3As2Se6-In3As2S3Se3 system

The In₃As₂Se₆-In₃As₂S₃Se₃ system has been investigated by methods of physicochemical analysis (DTA, X-ray powder diffraction, MSA) and by microhardness and density measurements. The phase diagram of the system, which is the quasi-binary section of the As-In-S-Se quaternary system, has been constructed. The region of the In₃As₂Se₆-based solid solutions is extended to 7 mol %, and the In ₃As₂S₃Se₃-based region to 15 mol %. A new quaternary compound In₆As₄S₃Se₉ is found in the system. Original Russian Text ? I.I. Aliev, R.S. Magammedragimova, A.A. Farzaliev, Dzh. Veliev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 4, pp. 691–694.     

Absorption and fluorescence of Ho3+ IN La2S3·3Ga2S3

Absorption bands of Ho³⁺ in vitreous La₂S₃·3Ga₂S₃ in the range 500 to 2000 nm were assigned. Excitation spectra reveal additional levels ⁵G₆ and ⁵F₃ obscured by the intrinsic absorption of the glass. The Ho³⁺ emission in chalcogenide glasses is more intense than in oxide glasses due to smaller non radiative relaxation as predicted by the theory of multiphonon relaxation.     

Phase equilibria in the CdI2-Ag2Se system

The phase diagram of the system CdI₂-Ag₂Se is studied by means of X-ray diffraction, differential thermal analysis and measurements of the density of the material. The unit cell parameters of the intermediate phase 2CdI₂·3Ag₂Se were determined a = 0.6387 Å, b = 4.311 Å, c = 4.044 Å; α = 113.72°, β = 90.27° and γ = 94.85°. The intermediate phase 2CdI₂·3Ag₂Se has a polymorphic transition at 125 °C. It melts incongruently at 660 °C.     

The non-isothermal crystallization kinetics of Sb2S3 in the (GeS2)0.2(Sb2S3)0.8 glass

The crystallization of Sb₂S₃ in the (GeS₂)_0.2(Sb₂S₃)_0.8 glass was studied under non-isothermal conditions. The influence of the sample form on crystallization was studied using bulk sample and two fractions of powder sample. The crystallization process of the sample in the form of powder was described using autocatalytic model, the crystallization of the bulk sample was described using nucleation-growth model. The parameters of both the models were determined.     

The structural interrelationship between the three polymorphs of Rh2O3 and Rh2S3, Rh2Se3, and Ir2S3

The syntheses of each of the three modifications of rhodium sesquioxide are reviewed and their infrared spectra are described. Models of each of these structures were constructed and manipulated using interactive molecular graphics. Their interrelationship is clearly described and used both to explain the similar features observed in their respective infrared spectra and to predict the occurrence of other discrete structures in the Rh₂O₃ system. Rhodium sesquisulfide, Rh₂S₃, is shown to be isostructural with the high pressure modification, II-Rh₂O₃.     

Phase relationships in the systems MSCr2S3In2S3 (M = Co,Cd, Hg)

The phase diagrams of the quaternary systems MSCr₂S₃In₂S₃, with M = Co, Cd, and Hg, were studied with the help of X-ray powder photographs of quenched samples, high-temperature X-ray diffraction patterns, DTA and TG measurements, and far-infrared spectra. Because indium sulfides do react with silica tubes, alumina crucibles must be used for annealing the samples. Complete series of mixed crystals are formed among the spinel-type compounds MCr₂S₄, MIn₂S₄ (M = Cd, Hg), and In₂S₃. HgIn₂S₄ is decomposed at temperatures above 300°C. In the sections CoCr₂S₄CoIn₂S₄ and CoCr₂S₄In₂S₃ relatively large miscibility gaps exist due to the change from normal to inverse spinel structure. But the interchangeability of both systems increases with increasing temperature, and at temperatures above 1000°C, complete series of solid solutions are formed, which can be quenched to ambient temperature. Superstructure ordering like that of ordered α-In₂S₃ has been found in the In-rich region of the MIn₂S₄In₂S₃ solid solutions. The unit cell dimensions of all stoichiometric and phase boundary compounds, e.g., Cd_1.15In_1.9S₄, including the chromium spinels MCr₂S₄ (M = Mn, Zn) and ZnCr₂Se₄, are given and discussed in terms of possible deviations from stoichiometry.