12185-17-0Relevant articles and documents
Preparation and some properties of high-purity PbGa2Se 4
Rigan
, p. 65 - 68 (2005)
Polycrystalline PbGa2Se4 was synthesized from commercially available and additionally purified Pb, Ga, and Se. As shown by chemical analysis, the material prepared from as-purchased reagents exhibited significant deviations from stoichiometry. According to microstructural analysis, this material contained a second phase. PbGa2Se4 synthesized from additionally purified Pb, Ga, and Se was uniform in composition. The highest degree of purification was ensured by the Bridgman-Stockbarger method, which enabled growth of stoichiometric single crystals. Attempts to purify PbGa2Se4 by directional solidification, zone melting, and thermal evaporation led to decomposition of the material. According to mass spectrometry results, the major products of PbGa2Se4 decomposition are PbGa2, Ga 2Se, Pb, and Se2.
The vapor composition vapor pressure of ZnSe from a modified knudsen technique between 1190 and 1310 K
Schoenherr,Freiberg,Siehe,Hartmann
, p. 1766 - 1771 (2007/10/03)
Solid ZnSe is evaporated from a Knudsen cell in vacuum. The effective molecular weight of the ZnSe vapor is directly determined by weighing the cell with and without effusion taking place. The rate of effusion is adjusted by a moveable furnace. An effective molecular weight of 135±5g/mol is found for temperatures between 1190 and 1310 K. The weight indicates the complete dissociation of the sublimed ZnSe into Zn and Se2 vapor. In that temperature range, the total equilibrium vapor pressure of solid ZnSe is estimated from the recoil force according to log10(P/kPa)= -(12896±96)K/T+(9.19±0.08). VCH Verlagsgesellschaft mbH, 1996.
Gaseous diffusion coefficients of ZnSe in Argon and Helium at 1140-1280 K and 70-100 mbar
Schoenherr,Freiberg,Hartmann
, p. 440 - 444 (2007/10/03)
The diffusion of subliming ZnSe in argon and helium gas has been investigated by a modified entrainment method with a flowing gas at a reduced pressure between 70 and 100 mbar. From the weight loss measurements an effective diffusion coefficient results for the (Zn+0.5Se2, Ar) system as 0.0828 (T/273)1.47 cm2/s and for the (Zn + 0.5Se2, He) system as 0.177(T/273)1.88 cm2/s between 1140 and 1280 K. With a simplified gas collision theory, rigid sphere diameters are estimated as 4.11 × 10-8 cm for Zn and 5.97 × 10-8 cm for Se2. VCH Verlagsgesellschaft mbH, 1996.
Thermodynamics of the thermal decomposition and formation of ytterbium (III) oxide selenide
Marx,Petzel
, p. 63 - 69 (2008/10/08)
The thermal decomposition of (YbO)2Se(s) was studied over the temperature range 1753-1997 K by the Knudsen effusion weight loss technique. It was found that the decomposition leads to a gas phase containing ytterbium and selenium with a molar ratio of 2:3 and to a residue of Yb2O3(s). Using literature and estimated enthalpy and entropy data for the gaseous species Yb, Se, YbSe and Se2, the principal decomposition reaction was established from the rates of effusion, and the second-law and third-law enthalpies and entropies were found for this reaction. A value of -1594±33 kJ mol-l is derived for the standard enthalpy of formation of (YbO)2Se(s). The feasibility of this value is discussed in view of the significant decrease in the formula volume accompanying the formation of (YbO)2Se from Yb2O3 and Yb2Se3.
Enthalpy of Formation of Tungsten Diselenide
Zelikman, A. N.,Kolchin, Yu. O.,Golutvin, Yu. M.
, p. 519 - 521 (2007/10/02)
The enthalpy of formation of tungsten diselenide has been measured calorimetrically by direct synthesis (ΔHo298 = -154.2 +/- 2 kJ mole-1).The dissociation pressure of tungsten diselenide has been measured by the Knudsen method in the range 1173-1423 K, and from the enthalpy of dissociation (ΔH = 259.6 +/- 4 kJ mole-1) a value of -151.4 +/-4 kJ mole-1 has been recalculated for the standard enthalpy of formation.
