Anne-Marie Loireau-Lozac'h

Verres formes par les sulfures L2S3 des terres rares avec le sulfure de gallium Ga2S3

Abstract Formation of glasses in the systems L 2 S 3 Ga 2 S 3 (L = Y and La to Er, and La to Er, except Eu). Conditions of preparation. Extent of the glassy regions as a fonction of the quenching temperatures and of the rare earth element. Crystallisation by heating: vitreous transition temperature Tg, and crystallisation temperature Tc. Mechanism of crystallisation. Preliminary study of the absorption spectra.

Preparation et structure de Ga2S3α type wurtzite lacunaire

Abstract Preparations of powdered and crystalline αGa 2 S 3 are described. Structure of αGa 2 S 3 is established from single crystal determination (R = 0.058). These is a superstructure of wurtzite type, with ordered vacancies on gallium positions. A polymorphism of Ga 2 S 3 is described.

Systèmes L2S3-Ga2S3 (L = La, Ce, Dy, Er et Y) diagrammes de phases

Abstract The intermediate phases are: L 6 Ga 10 3 S 14 hexagonal, Ce 6 Al 10 3 S 14 -type, for L: La to Tb, and Y, which have an order disorder transition; LGaS3 of unknown structure for L = La and Ce; L3GaS6, orthorhombic Er3GaS6-type, for L = Dy to Er and Y. Description of the 5 phase diagrams. In each case the formation of glasses is closely related to the phase diagram.

Diagramme de phase du systeme Ga2Se3CdSe

The phase diagram contains : a) a congruent melting CdGa2Se4 compound, which is dimorphous. The two varieties have the same tetragonal CdGa2S4 type structure, with an order-disorder transition at 830°C. b) a blende-type solid solution from Ga2Se3 to n = 0.18. c), a wurtzite-type solid solution, from CdSe to n = 0.65 which has an eutectoid point at n = 0.70 and 704°C. (n = CdCd + Ga atomic) .

Spectres vibrationnels, transitions electroniques et structures a courtes distances dans les verres: Sulfures de terres rares - sulfure de gallium

Absorption spectra of chalcogenide glasses of general formula Ln/sub 2/S/sub 3/-1,8Ga/sub 2/S/sub 3/ (Ln = La/sup +3/, Ce/sup +3/, Pr/sup +3/, Nd/sup +3/, GD/sup +3/) were investigated continuously from far infrared to ultra-violet region. Raman spectra were recorded in the 5cm/sup -1/ to 600 cm/sup -1/ range. Vibrational spectra of glasses have been compared to those of polycrystalline compounds Ln/sub 10///sub 3/Ga/sub 6/S/sub 14/ (Ln = La/sup +3/, Ce/sup +3/) and Ln/sub 6/Ga/sub 10///sub 3/S/sub 14/ (Ln = La/sup +3/ to Gd/sup +3/). From the observed spectra it could be concluded that the short distance around gallium atom is strongly modified in going from crystalline to glassy state. Electronic transitions of Ce/sup +3/, Pr/sup +3/ and Nd/sup +3/ ions have been also identified in the visible region and in the mid infrared absorption spectra.

Verres formes par les oxysulfures de terres rares Ln2O2S

Abstract Glass formation in the Ln 2 O 2 S-Ga 2 S 3 systems (Ln = La to Nd). Preparations. Extent of the glassy regions as a fonction of the R.E. content and of the nature of the R.E. : Vitreous transition temperatures and crystallization temperatures. Microhardness. Optical properties.

Verres du systeme La2S3La2O3Ga2O3Ga2S3

Abstract The extent of the glass forming region is described as a function of the composition and of the cooling speed. The shape of this region is explained from the previously described La2S3La2O3Ga2O3Ga2S3 phase diagram. Glasses are obtained after relatively slow cooling (5°/min), in a definite region of compositions, which coincides with a relatively large concentration of ternary invariants. The thermal properties (transition temperatures and crystallization temperatures) were measured by DTA. For a relatively large region of compositions, glasses return to the equilibrium conditions with intermediate formation of the La3.33Ga6S12O2 metastable crystalline phase. An approach to the structure of the glasses is made by comparison with the crystal structures of the numerous ternary and quaternary crystalline compounds observed in the system, and by the comparison of the Raman spectra. It appears that these gallium oxysulfide glasses have many structural analogies with germanium sulfide glasses.

Système ternaire La2Se3-Ga2Se3-GeSe2 diagramme de phase — Etude des verres

Abstract Existence of a solid solution, hexagonal Ce 6 Al 10 3 S 14 -type, between La 6 Ga 10 3 Se 14 and La6Ge2.5Se14 compounds. Location of the eutectic valleys and ternary eutectic (650°C, for La2Se3, 3 Ga2Se3, 14 GeSe2). Level curves of the liquidus. Obtention of glasses in a large domain of composition, along the eutectic valley. Measurements of Tg and crystallisation temperature.

Variation, avec la composition, des indices de refraction des verres de sulfures de lanthane et de gallium et indices de quelques verres apparentes

Abstract Microscopic measurements of reflectance of glasses made from lanthanum sulfide and gallium sulfide allow the determination of the refractive indices and their dispersion through the visible spectrum. The indices vary within the range 2.3–2.6 as a function of the relative proportion of La and Ga. Some other measurements deal with glasses of lanthanum oxysulfide and europium monosulfide.

Étude du système La2S3La2O3Ga2O3Ga2S3: Description structurale des phases quaternaires et approche du diagramme de phase

A description and structural study of four quaternary compounds is furnished: (LaO)/sub 4/Ga/sub 1,33/S/sub 4/ and ..cap alpha..-LaGaS/sub 2/O have sheet structures, formed by (LaO) sheets and gallium sulfide sheets. La/sub 3/GaS/sub 5/O has a ribbon structure, formed by (La/sub 2/O) ribbons inside a LaGaS/sub 5/ sulfide skeleton. In the three preceding compounds, oxygen is bound only to lanthanum, and gallium is bound only to sulfur. No such bond selectivity occurs in ..beta..-LaGaS/sub 2/O and La/sub 3,33/Ga/sub 6/S/sub 12/O/sub 2/. An interpretation of the structural characteristics of the Ga - (O,S) arrangements is presented in relation to the composition. A partial description of the phase diagram (for O/O + S) < 0.50) is presented. The La/sub 2/O/sub 2/S-Ga/sub 2/S/sub 3/ system is quasi-binary. The La/sub 2/O/sub 3/-Ga/sub 2/S/sub 3/ system is a section in the ternary system, involving three-phase equilibria. A description of the eutectic valleys and of the ternary invariants is furnished. 23 references, 8 figures, 5 tables.