R. Ollitrault-Fichet

Les composes Ag7AsS6 et Ag7AsSe6 etude des proprietes thermiques, cristallographiques et electriques

The preparation and the partial phase diagrams Ag2X“As2X5” (X = S or Se) are described. Peritectic decompositions occur at 560°C for Ag7AsS6 and 360°C for Ag7AsSe6. Phase changes are observed at 250°C for Ag7AsS6 and 150°C for Ag7AsSe6. For each compound, the low temperature form is cubic P213, and the high temperature form has the Ag8GeTe6 structural type, F43m. The high temperature forms are not quenchable. Ionic and electronic conductivity have been measured in Ag7AsS6 and Ag7AsSe6. Ionic conductivity was measured using RbAg4I5 as a blocking electrode for electronic conduction. Electromotive force measurements confirm transference numbers. At room temperature, ionic conductivities were 1,5.10−6 (Ω.cm)−1 and 0,08 (Ω.cm)−1 for Ag7AsS6 and Ag7AsSe6 respectively.

The As-Te system: phase diagram and glass separation

Abstract The As 2 Te 3 compound is usually described as showing non-congruent melting, or congruent melting at a temperature which cannot be differentiated from that of the next eutectic. The As-Te system is here presented using an isochoric diagram, and the specific volume variable is taken into account to explain this anomalous melting. From analyses by electron microprobe of quenched liquid and vapour phases, it may be assumed that the melting of As 2 Te 3 is non-congruent. Vitreous materials are obtained from quenching of the liquid in two zones adjacent to As 2 Te 3 , and from fast quenching of liquid As 2 Te 3 . When glassy products containing 55–80 mol% of As are annealed at temperatures lower than that of the liquidus, separation of a large vitreous phase occurs.

Verres du systeme AgAsSe

Abstract Description of the glass former region, in connection with the previously described phase diagram. Formation of two-phase glasses from liquid miscibility gap. Description of the thermal behaviour: Tg, Tc. Mechanism of crystallization. Obtention of glasses after slow cooling. Influence of thermal treatments of the glassy samples on Tg and Tc. Infrared spectroscopy in the range 100 – 600 cm −1 .

Description du système ternaire AgSbSe

Abstract The phase diagram of the AgSbSe system was studied by differential thermal analysis, X-ray diffraction and metallography analysis. Two ternary phases were observed: the AgSbSe 2 compound, an f.c.c. NaCl-like structure with congruent melting and a new phase, to which the formula Ag 3 Sb 7 Se 12 is attributed. This last compound is dimorphic and the transition between the two forms occurs at about 200 °C. The high temperature structure disappears at about 360 °C. Four quasi-binary sections are described in this ternary system. Seven ternary invariants are characterized: five eutectics of which two are degenerated at the selenium apex, and two peritectics. In the temperature range between 360 and 558 °C, besides the seven three-phase domains, there are five two-phase domains. Three ternary liquid-liquid miscibility gaps are observed, of which only two are crossed by a valley. Finally, a glass domain with a small extension, which comes from a binary glass zone rich in selenium of the SbSe system, was established within the (AgSbSe 2 )SeSb 2 Se 3 triangle.

Système AsGeTe: II. Diagramme de phase du système ternaire AsGeTe

The AsGeTe system is formed by three independent triangles, corresponding to the two quasibinary systems GeAsGeTe and As2Te3GeTe. The presence of four phases As2GenTe3+n (n = 1 to 4) having peritectic decomposition introduces eight ternary peritectic invariants, whose temperatures and compositions are described. The three ternary eutectics have the following characters: E1, As19Ge52Te29 (662°C); E2, As42Ge5Te53 (368°C); E3, As22Ge5Te73 (350°C).