Phase equilibrium and growth of homogeneous crystals in the γLa2S3  γNd2S3 system

T-x diagram of the γLa₂S₃  γNd₂S₃ system was plotted for the temperature interval 1400–2100°C. γLa₂S₃ and γNd₂S₃ form unlimited solid solutions of the substitution type. Basing on this phase diagram the theoretical distribution curves of Nd₂S₃ along the ingot of length were calculated. The experimental distribution curves were determined by chemical and electron microprobe measurements of La and Nd content in γ(La,Nd)₂S₃ ingots directionally solidified from the melt of different composition. Character of the component distribution in the ingots shows that diffusion of neodymium and lanthanum is exeptionally fast at 1700–2000°C. This phenomenon is explained by vacancy diffusion mechanism in γLa₂S₃  γNd₂S₃ solid solutions. Crystal structure of these solid solutions belongs to Th₃P₄ type with high concentration of randomly distributed cation vacancies.     

The preparation of some ternary sulphides MR2S4 (M = Ca,Cd; R = La,Sm,Er) and the melt growth of CaLa2S4

The Preparation of the binary sulphides CaS, La₂S₃, Er₂S₃, and Sm₂S₃ in high purity powder form from the elements is described, with the subsequent synthesis of ternary sulphides with Th₃P₄ and spinel structures. Single crystals of CaLa₂S₄ and CaLa₂S₄La₂S₃ solid solutions, up to 10 mm³ volume, have been grown from the melt in sealed crucibles using the Stöber technique.     

Heat capacity of the n -Bi2Te2.88Se0.12 and p -Bi0.52Sb1.48Te3 solid solutions

The heat capacity of the n-Bi₂Te_2.88Se_0.12 and p-Bi_0.52Sb_1.48Te₃ solid solutions has been measured from 360 to 600 K. The data, represented in the form C _p = a + bT + cT ⁻², have been used to evaluate the thermodynamic functions of the solid solutions in the range 298.15 to 600 K. Original Russian Text ? Yu.I. Shtern, A.s. Malkova, A.S. Pashinkin, V.A. Fedorov, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 10, pp. 1184–1186.     

Die strukturen von BaGa2S4 und BaAl2S4

The isotypic compounds BaGa₂S₄ and BaAl₂S₄ crystallize in the cubic system, space group Pa3 with the constants: BaGa₂S₄: a = 1268.5±0.4 pm, BaAl₂S₄: a = 1265.0±0.7 pm. BaS₄- resp. AlS₄-tetrahedra are connected by common corners to a threedimensional net. The Ba-ions are located in holes with coordination numbers 6 resp. 12.     

Zur kenntnis von Na2Cu4S3 und KCu3Te2

The crystal structures of the new compounds Na₂Cu₄S₃ and KCu₃Te₂ have been solved. Na₂Cu₄S₃ crystallizes in the K₂Ag₄S₃ structure (space group: C2/m, a = 1563(3) pm, b = 386(2) pm, c = 1033(2) pm, β = 107.6^o, N = 4), KCu₃Te₂ in the CsAg₃S₂ structure (space group: C2/m, a = 1645.3(9) pm, b = 429.4(4) pm, c = 866.1(6) pm, β = 111.86^o, N = 4).     

Etude cristallographique du systeme FeSSc2S3 preparations et structures de FeSc2S4 et Fe0.85Sc2.10S4

The crystal structures of FeSc₂S₄ and Fe_0.85Sc_2.10S₄ have been determined by three dimensional X-ray diffraction. The cubic cells, space group Fd3m, have lattice constants $\text{a}\text{= 10,501}\text{A}\text{?}$ for FeSc₂S₄ and $\text{a}\text{= 10,444}\text{A}\text{?}$ for Fe_0.85Sc_2.10S₄. Iron is divalent and scandium trivalent. FeSc₂S₄ is a direct spinel structure, Fe_0.85Sc_2.10S₄ is near a spinel structure. Only 0,5 iron atom is on every 8a position; 0,175 Fe and 1,05 Sc lie on octahedral 16d and 16c site.     

Complete oxidation of acetaldehyde on Pt/CeO2-ZrO2-Bi2O3 catalysts

Pt/CeO₂-ZrO₂-Bi₂O₃ catalysts for catalytic combustion of acetaldehyde, which is one of volatile organic compounds (VOCs), were prepared by a wet impregnation method in the presence of polyvinylpyrrolidone K25 (PVP). The addition of PVP in the preparation process was effective to enhance the specific surface area and the Pt²⁺ ratio on the surface. Additionally, the pore volume and size of the catalysts were modified by the PVP addition. The Pt/CeO₂-ZrO₂-Bi₂O₃ catalysts are specific for the total acetaldehyde oxidation and CO and any acetaldehyde-derivative compounds were not observed as by-products. The catalytic activity of the Pt/CeO₂-ZrO₂-Bi₂O₃ catalysts was significantly promoted by the PVP addition and the total oxidation temperature decreased. By the optimization of the amount of platinum, the complete oxidation of acetaldehyde was realized at a temperature as low as 140 °C on a 10 wt%Pt/CeO₂-ZrO₂-Bi₂O₃ catalyst.     

Crystal structure of cubic MnSc2S4 and Mn2.29Sc1.14S4

The crystal structure of MnSc₂S₄ ($\text{a}\text{= 10.613}\text{A}\text{?}$, space group Fd3m) and Mn_2.29Sc_1.14S₄ ($\text{a}\text{= 10.523}\text{A}\text{?}$, space groupe Fd3m) were determined by three dimensional X-Ray diffraction. MnSc₂S₄ is a normal spinel structure and the atomic distribution shows that Mn_2.29Sc_1.14S₄ structure is intermediate between the rocksalt (MnS) and the spinel (MnSc₂S₄) types. Similar behaviour of Mn and Fe atoms in MnSSc₂S₃ and FeSSc₂S₃ systems was observed.     

Glass formation and properties of novel GeS2-Sb2S3-In2S3 chalcogenide glasses

Novel chalcogenide glasses based on GeS₂-In₂S₃-Sb₂S₃ system were prepared by conventional melt-quenching method and their physicochemical properties, e.g. glass transition temperature, density, and Vickers micro-hardness, were studied in detail. The results show that the thermal, mechanical, and optical properties depend largely on four-coordinated Ge or In entities and are sensitive to the variation of the connectivity in the GeS₂-In₂S₃-Sb₂S₃ glass network. It is a promising chalcogenide glass system suitable for rare earth doping or crystallization of rare earth doped crystals, which aims at optical applications of IR optical amplifier or efficient solid state laser.     

Magnetic semiconducting spinels in the mixed system Co1−xFexCr2S4

The ferrimagnetic spinels CoCr₂S₄ (T_C ≈ 220 K) and FeCr₂S₄ (T_C ≈ 180 K) were found to form a complete series of solid solutions. The mixed compounds are semiconductors with Curie temperatures varying almost linearly with the composition. The iron is concluded to be divalent in the whole composition range. All samples exept CoCr₂S₄ are p-conducting, with negative magnetoresistance values close to that of p-FeCr₂S₄.The possibilities to incorporate trivalent iron into CoCr₂S₄ are discussed.     

Systeme Ga2S3FeS — Diagramme de phase — etude cristallographique

The system was studied by DTA, X-ray diffraction and in particular by the Guinier-Lenné method. Eight intermediate phases are described. 1) Three solid solutions in the Ga₂S₃ region : a) a wurtzite-type solid solution (T > 1000° C ; 0.05 < n < 0.23) (n = Fe $\text{at}\text{Fe}$ at+Ga at), b) a blende-type solid solution (700°C < T < 980°C ; 0.10 < n < 0.20) with many stacking faults, c) a non-stoichiometric hexagonal phase α'Ga₂S₃ type (T < 700°C, 0.07 < n < 0.12). 2) for n = 0.20 and T = 540°C a superstructure of orthorhombic wurtzite-like array FeGa₄S₇. 3) From n = 0.20 through n = 0.27, a non stoichiometric superstructure of tetragonal-like array has the CdGa₂S₄ type (600°C < T < 1030°C). 4) For n = 0.33, the FeGa₂S₄ has two forms depending from the temperature : a) a low temperature form is trigonal ; b) a high temperature form is orthorhombic type ZnAl₂S₄. Transition temperature is 1010°C. 5) For n = 0.50, Fe₂Ga₂S₅ polytypes : a) Fe₂Ga₂S₅α 1T type Mn₂Ga₂S₅ ; b) Fe₂Ga₂S₅ 2H ; c) Fe₂Ga₂S₅ 3R type Mn₂Al₂Se₅. A phase diagram is proposed.     

Topotactic redox reactions of the channel type chalcogenides Mo3S4 and Mo3Se4

Mo₃S₄ and Mo₃Se₄ were found to undergo topotactic electron-ion exchange reactions at ambient temperatures in aqueous and non-aqueous electrolytes containing transition or main group cations. The products of cathodic reduction are ternary phases A_xMo₃X₄. Mobilities of the exchangeable cations are rather high inside the solid and are responsible for high reaction rates. Cathodic reduction of Mo₃S₄ and Mo₃Se₄ represents a suitable method for the preparation of both stoichiometric and nonstoichiometric ternary phases which are of interest with respect to the superconducting properties of these chalcogenides.     

Subsolidus phase equilibria in the RuO2-Bi2O3-ZrO2 system

Subsolidus equilibria in air in the RuO₂-Bi₂O₃-ZrO₂ system were studied with the aim of obtaining information on possible interactions between a Bi₂Ru₂O₇-based cathode and a ZrO₂-based solid electrolyte in solid-oxide fuel cells (SOFCs). No ternary compound was found in the system. The tie lines are between Bi₂Ru₂O₇ and ZrO₂, and between Bi₂Ru₂O₇ and gamma-Bi₂O₃—the ZrO₂ stabilised Bi₂O₃ phase, stable at temperatures over 710 °C.     

Synthesis of Sb2S3 peanut-shaped superstructures

Peanut-shaped Sb₂S₃ superstructures have been synthesized via a hydrothermal process at 120 °C for 8 h using hydrochloric acid and antimony O-benzyl dithiocarbonate (benzylxanthate, Sb(S₂COC₇H₇)₃) as starting materials. The powder X-ray diffraction (XRD) pattern shows the product corresponds to the pure orthorhombic phase of Sb₂S₃, the purity and composition of which are further confirmed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies reveal that the peanut-shaped Sb₂S₃ superstructures are aggregated by nanorods. The possible mechanistic pathways in the formation of the structures are discussed.     

Phase investigations in the system PbSIn2S3 and the crystal structures of PbIn2S4 and Pb6In10S21

The system PbS-In₂S₃ was examined by differential thermal analysis (DTA), chemical vapour transport (CVT), and X-ray diffraction. Five new phases of compositions closely related to the 1:1 ratio were found and prepared as needle-shaped single-crystals; their crystal data are reported. The structures of PbIn₂S₄ (orthorhombic, Pnma, a=11.688(1), b=3.8528(1), $\text{c}\text{=13.763(1)}\text{A}\text{?}$, Z=4) and Pb₆In₁₀S₂₁ (monoclinic, C2/m, a=27.629(3), b=3.8630(5), $\text{c}\text{=15.705(2)}\text{A}\text{?}$, β=95.9°, Z=2 were solved from 808 resp. 3554 independent reflexions and refined to R=0.116 resp. 0.068. In both structures the In-S coordination polyhedra are distorted octahedra, the Pb-S polyhedra are distorted bicapped trigonal prisms.     

Preparation and properties of ZnIn2S4 thin films

ZnIn₂S₄ thin films prepared by flash evaporation are polycrystalline and exhibit the structure of ZnIn₂S₄ on X-ray analysis. The films are photoconducting with a dark resistivity of about 10³ ω cm. At low temperatures, when illuminated by gap energy light and subsequently measured in the dark, the films exhibit a residual conductivity which can be removed by heating the samples to room temperature.     

Die strukturen des MgAl2S4 und Mg0.830In2.113S4

MgAl₂S₄ crystallizes in the orthorhombic system, space group Pnma (No 62) with the lattice constants: a=1251.1 ± 0.6 pm, b =722.0 ± 0.4 pm, c=592.1 ± 0.4 pm The compound is isotypic to BeAl₂O₄.Mg_0.830In_2.113S₄ forms the spinel structure, space group Fd3m (No 227) with a=1071.9 ± 0.6 pm.     

Phase relationships of the ternary chromium sulfides CrII1−xMxCrIII2S4 (M = Mn,Fe, Co) with Cr3S4 and spinel structure

The phase diagrams of the chromium sulfide systems Cr_1?xM_xCr₂S₄, Cr_1?xFe_xCr₂S₄, andCr_1?xCo_xCr₂S₄ were studied with the help of X-ray powder Guinier photographs of quenched samples. The phase widths of the monoclinic Fe₃Se₄ (Cr₃S₄) type solid solutions increase with increasing temperature from x < 0.1 below 500°C to x = 0.23, 0.45, and 0.44 for M = Mn, Fe, and Co, respectively, at 900°C. The observed alterations of the unit cell parameters, e.g. increase of the volume V, but decrease of the lattice constant a with increasing × for M = Mn and Fe, are discussed in terms of the ionic radii and metal-semiconductor transitions. The phase widths of the spinel type chromium sulfides MCr₂S₄ are very small for all temperatures studied. The relative stability of the Cr₃S₄ and the spinel structure can be interpreted using site preference and covalent bonding arguments.     

Systeme Ga2S3PbS diagramme de phase,etude cristallographique

Four intermediate phases are present ; PbGa₂S₄,orthorombic EuGa₂S₄-type (a = 20,44 ; b = 20,64 ; $\text{c}\text{= 12,09}\text{A}\text{?}$) ; Pb₂Ga₂S₅, orthorombic space group Pbca (a = 12,38 ; b = 11,90 ; $\text{c}\text{= 11,03}\text{A}\text{?}$) ; and two Ga₂S₃-rich solid solutions, one of the wurtzite type at temperatures above 1000°C, one of the distorded blende type below about 970°C. PbGa₂S₄ has a peritectic decomposition at 930°C, and Pb₂Ga₂S₅ at 900 ± 5°C. The eutectic is at 730°C for about n = 0,80 ($\text{n}\text{=}\text{Pb}\text{Pb+Ga}$ atomic). A glassy region is obtained by quenching the liquid phase and its extent depends on the quenching temperature (at 1000°C, between n = 0,25 and n = 0,50).