NON-STOICHIOMETRY IN CADMIUM SELENIDE AND EQUILIBRIA IN THE SYSTEM CADMIUM-SELENIUM<sup>1</sup>

Reisman, Arnold; Berkenblit, M.; Witzen, M.

doi:10.1021/j100817a032

Cited by 54 publications

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“…Although early investigations (1,4,5) indicated the above mode of sublimation for CdSe, later studies (2,3) suggested that the sublimation of CdSe is not completely congruent. Reisman (2) found that stoichiometric CdSe sublimes at about 400~ to form a selenium-rmh gas phase and a selenium-deficient nonstoichiometric solid residue. Berkowitz and Chupka (3) conclude from mass spectrometric studies that stoichiometric CdSe does not sublime congruently.…”

Section: Congruency O] Cadmium Selenide S~blimation--itmentioning

confidence: 99%

Solid-Gas Phase Equilibria and Thermodynamic Properties of Cadmium Selenide

Sigai

Wiedemeier²

1972

J. Electrochem. Soc.

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The investigation of the solid-gas phase equilibrium of CdSe revealed that at about 400~ CdSe sublimes initially by losing selenium to form nonstoichiometric CdSet-z, where x ~ 0.002; the resulting compound CdSel-x sublimes congruently. Since existing thermodynamic data for CdSe are either incomplete or show significant differences, the high-temperature thermodynamic properties of CdSe were reinvestigated using the Knudsen effusion technique.With the heat capacity function for CdSe (s) (C~ : 12.36 + 1.45 • 10 -3 T eu [320~176 measured for the first time in this work and with tabulated thermochemical data, the vapor pressure measurements were evaluated in terms of the standard heat of formation [~H~ = --35.7 -~ 1.0 kcal/mole (third-law evaluation)] and the absolute entropy [S~ = 19.6 _ 1.2 eu (second-law evaluation)] of CdSe(s). Previous investigations are reviewed and compared with present results.Several investigations of the mode of vaporization (1-3) and high-temperature thermodynamic properties (1, 4-8) of CdSe have been performed because of its potential use in solid-state devices and their importance for the growth of single crystals from the vapor phase. However, the precise mode of vaporization of CdSe is still uncertain and existing thermodynamic data are incomplete or show significant discrepancies. An experimentally determined heat capacity function of CdSe has not been reported prior to this work.A knowledge of the equilibrium vapor pressure of CdSe is important since earlier investigations of CdSe (9-11) and other II-VI compounds (12) have demonstrated that these types of materials generate native point defects which are electrically active and play a substantial role in determining the electrical and optical properties of these compounds. Therefore, it is essential to define the conditions of preparation and any subsequent treatment of the specimen with respect to the equilibrium partial pressures of the components for a reliable interpretation of electrical and optical measurements. Solid-Gas Phase EquilibriaGeneral form of vaporization reaction.--Mass spectrometric data (1) and vaporization studies on CdSe in the presence of excess elemental Cd or Se in the gas phase (7) indicate that CdSe(g) and higher molecular weight species than Se2(g) are negligible under present experimental conditions. Therefore, the congruent sublimation of CdSe can be described by the reactionwhere a is the degree of dissociation of Se~(g). Wiedemeier and Goyette (13) have developed a calculational technique to compute a for this type of reaction from Knudsen data and the dissociation energy of the chalcogen species. With a dissociation energy for Se2 (g) of 75.7 kcal/mole (14) and with experimental data of the CdSe sublimation to be presented later, a was found to be less than 0.1% over the entire temperature range of this investigation. Therefore, monatomic cadmium and diatomic selenium are the only predominant species in the gas phase. This is in agreement with earlier mass spectrometric work (1). Congruency o] cadmiu...

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Section: Congruency O] Cadmium Selenide S~blimation--itmentioning

confidence: 99%

Solid-Gas Phase Equilibria and Thermodynamic Properties of Cadmium Selenide

Sigai

Wiedemeier²

1972

J. Electrochem. Soc.

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“…We take the values of a and 03B2 determined by Jordan [11]. The experimental phase diagrams of Reisman, Berkenblit and Witzen [21] ] and Burmeister and Stevenson [22] are used for the system cadmiumselenium. The Te side of the liquidus of HgTe is taken from a compilation of data by Hansen [9], and from references [23] and [24].…”

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confidence: 99%

Thermodynamics and phase diagram calculations in II-VI and IV-VI ternary systems using an associated solution model

Laugier

1973

Rev. Phys. Appl. (Paris)

136

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To cite this version:A. Laugier. Thermodynamics and phase diagram calculations in II-VI and IV-VI ternary systems using an associated solution model. Revue de Physique Appliquee, 1973, 8 (3) Abstract. 2014 The thermodynamic properties and the T-x phase diagrams for liquid-solid equilibrium in II-VI and IV-VI ternary systems are described by a regular associated liquid solution model derived from that used by Jordan for ZnTe and CdTe and by the regular approximation for the solid solution. For the pseudo-binary systems exhibiting miscibility in both phases and monotonic variation of the liquidus and solidus curves, a general expression is obtained. It is independent of the interactions in the liquid, and is the same as for ideal non associated liquids. In the calculation of the ternary T-x phase diagrams five parameters are needed : the two interaction parameters 03B11, 03B12, the two coefficients of dissociation, 03B21, 03B22, obtained from the respective binary liquidus, and the interaction parameter W in the solid, derived from the pseudo-binary phase diagrams. Good agreement with experimental data is obtained for the pseudo-binary systems : ZnTe-CdTe, ZnTe-HgTe, ZnSe-ZnTe, CdTe-HgTe, CdTe-CdSe, HgTe-HgSe, PbSe-PbTe, PbTe-SnTe, and for the ternary systems : Zn-Cd-Te and Pb-Sn-Te. The theory is especially suited for the case 03B2 ~ 0 and 03B1 is small. It is applied to the calculation of the chalcogen-rich part of the ternary systems : Cd-Hg-Te and Cd-Se-Te.

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“…Let us suppose that the solute bismuth dissolves in or reacts with the fused bismuth trichloride solvent to form two molecular species Xn and Xm. Conservation of mass requires that Ml -DnMn + DmMja (1) where Mn and Mm are, respectively, the molar concentrations of Xn and Xm, and where Dn and Dm are the numbers of moles of solute bismuth required to form one mole, respectively, of Xn and of Xm, The law of additive absorbances may be written…”

Section: Discussionmentioning

confidence: 99%

SPECTRA OF DILUTE SOLUTIONS OF BISMUTH METAL IN MOLTEN BISMUTH TRIHALIDES. I. EVIDENCE FOR TWO SOLUTE SPECIES IN THE SYSTEM BISMUTH—BISMUTH TRICHLORIDE¹

Boston¹,

Smith²

1962

J. Phys. Chem.

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Solute bismuth metal in chloride-rich melts of the system Bi-BiCl3 is found to be partitioned into two chemical species which obey the law of additive absorbances. ilbsorption spectra from 450 to 750 mp are reported for molten Bi-BiClr mixtures 0.0027 to 0.7 AI in solute bismuth metal a t path lengths as short as 24 p and a t temperatures of 264, 350, and 433".The spectrum consists of an intense, broad band with a maximum near 560 m p . Large apparent deviations from Beer's law are found a t all wave lengths. These spectra have the characteristics expected for solutions with two light-absorbing solute species. Phenomenological equations are derived which describe the spectra of solutions consisting of any given number of solute species derived from a common substance,

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NON-STOICHIOMETRY IN CADMIUM SELENIDE AND EQUILIBRIA IN THE SYSTEM CADMIUM-SELENIUM¹

Cited by 54 publications

References 0 publications

Solid-Gas Phase Equilibria and Thermodynamic Properties of Cadmium Selenide

Solid-Gas Phase Equilibria and Thermodynamic Properties of Cadmium Selenide

Thermodynamics and phase diagram calculations in II-VI and IV-VI ternary systems using an associated solution model

SPECTRA OF DILUTE SOLUTIONS OF BISMUTH METAL IN MOLTEN BISMUTH TRIHALIDES. I. EVIDENCE FOR TWO SOLUTE SPECIES IN THE SYSTEM BISMUTH—BISMUTH TRICHLORIDE¹

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NON-STOICHIOMETRY IN CADMIUM SELENIDE AND EQUILIBRIA IN THE SYSTEM CADMIUM-SELENIUM1

Cited by 54 publications

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Solid-Gas Phase Equilibria and Thermodynamic Properties of Cadmium Selenide

Solid-Gas Phase Equilibria and Thermodynamic Properties of Cadmium Selenide

Thermodynamics and phase diagram calculations in II-VI and IV-VI ternary systems using an associated solution model

SPECTRA OF DILUTE SOLUTIONS OF BISMUTH METAL IN MOLTEN BISMUTH TRIHALIDES. I. EVIDENCE FOR TWO SOLUTE SPECIES IN THE SYSTEM BISMUTH—BISMUTH TRICHLORIDE1

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NON-STOICHIOMETRY IN CADMIUM SELENIDE AND EQUILIBRIA IN THE SYSTEM CADMIUM-SELENIUM¹

SPECTRA OF DILUTE SOLUTIONS OF BISMUTH METAL IN MOLTEN BISMUTH TRIHALIDES. I. EVIDENCE FOR TWO SOLUTE SPECIES IN THE SYSTEM BISMUTH—BISMUTH TRICHLORIDE¹