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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 = Cd Cd + Ga atomic) .

The trivalent rare earth sulfides (La to Gd, Eu excepted), combine with US2 and give Ln2US5 orthorhombic sulfides, spatial group Pnma, U3S5-type. The crystal structure of SmIII2US5 is established from single crystals determinations (R = 0,05) : the atomic positions are identical to those of U3S5. These compounds form continuous solid solutions with U3S5 by substitution of LnIII by UIII, and partial solid solutions with US2 by a mechanism involving substitution of LnIII by UIV and vacancies. The two compounds EuIIU2S5 and SmIIU2S5 are isostructural with the preceding ones, from a single crystal study. A continuous passage from SmIII2US5 to SmIIU2S5 and to U3S5 is observed.

Going from La 2 S 3 to Bi 2 S 3 ( n = Bi La + Bi ) the authors observe : 1. 1) at lower temperatures a solid solution, orthorhombic, of the α-La 2 S 3 type, having a peritectic decomposition at about 1080°C for n = 0.15 at higher temperatures a solid solution, tetragonal, of the β-La 2 S 3 type (or La 10 S 14 O - type). These two solid solutions have similar extents, going from n = 0 to about n = 0.15; 2. 2) a La 4 Bi 2 S 9 orthorhombic phase, ordered form of the phase Ce 1.2 Bi 0.8 S 3 previously described in the Ce 2 S 3 Bi 2 S 3 system. It has a peritectic decomposition at 890°C; 3. 3) a phase of probable composition LaBiS 3 , of unknown structure, having a peritectic decomposition at 860°C; 4. 4) a solid solution of the Bi 2 S 3 -type, which gives a peritectoid transformation at 780°C for about n ≅ 0.95; 5. 5) a degenerated eutectic near Bi 2 S 3 at 775°C.

Existence of a very large glassy domain inside the ternary system EuSGa 2 S 3 GeS 2 . Conditions of formation of the glassy products. Thermal properties : glass trarsition temperatures and crystallization temperatures. Existence in the ternary system of a large region of glass having a very small crystallization speed. Refractiv index. Magnetic moment. Structural study by Raman spectroscopy of crystalline compounds (GeS 2 , EuGeS 3 , Eu 2 GeS 4 , EuGa 2 S 4 ) and of various glasses of this system.

Metastable phases are observed in the Ga2S3-MnS system. They have tetrahedral structures : superstructures of the wurtzite (σ1, σ2, σ3) and superstructures of the zinc blende (σ4 and σ5). They are obtained by various heat treatments of the metastable wurtzite type solid solution which is prepared by quenching from 1000–1100°C. These metastable σn phases come back to equilibrium state with heat evolution and formation of the characteristic stable phases of the equilibrium phase diagram. A large hysteresis is observed when the melted products are progressively cooled at constant speed (0.1 or 2 or 6°/min) and different phase diagrams, out of equilibrium, are described.

The compound (LaO)4Ag1 · 5Ga1 · 5S5 belongs to the quasi-binary La2O2SAgGaS2 system. It undergoes a peritectic decomposition at 1040°C and a order-disorder transition at 750°C. The high temperature variety is tetragonal, with a 0 = 4.18 A ; c 0 = 18.74 A ; Z = 1; space group 1422; it has the same structural type as (CeO)4Ga2S5. The low temperature variety is an orthorhombic superstructure of the preceding one. with a = 17.58 (3 a0√2); b = 5.90 (a0√2) and c = 18.66 A (c0). The electrical conductivity is mainly of ionic nature. The e.m.f. measurements of a cell Ag/(LaO)4Ag1 · 5Ga1 · 5S5/S.C./Pt support this conclusion.

The system is studied by D.T.A. and X rays diffraction methods. Several intermediate phases are observed. First of all, a very extended solid solution, from Ga2Se3 to n = 0,36 n = Mn at ( Mn at + Ga at ) is only obtained by quenching the melt. It has a tetrahedral structure going from wurtzite to blende with increasing content of MnSe. It is a metastable phase, at all temperatures for which the solids exist. It does not belong to the phase diagram. In the phase diagram are only present the following phases : 1. 1o - from n = 0 to n = 0.15 : a solid solution with a disturbed blende structure (odd h k 1 reflections are diffuse and a no-coherent parameter is calculated). 2. 2o - for n = 0.33, the MnGa2Se4 compound, which is dimorphous ; it has a tetragonal structure at low temperature, of the CdGa2Se4 type (as the ϕ6 phase of the Ga2S3-MnS system, but exactly stoichiometric for the selenide). At high temperature it has an orthorhombic structure of the ZnAl2S4 type (as the high temperature form of MnGa2S4). The transition occurs at 924°C. The compound undergoes a peritectic decomposition at 955°C. The eutectic is at 943°C and about n = 0.40.

The system was studied by DTA, X-ray diffraction and in particular by the Guinier-Lenne 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 at Fe at+Ga at), b) a blende-type solid solution (700°C

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.

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.

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.

The pseudo-binary system AgI-BiI 3 has been studied by differential thermal analysis (DTA) and by microcalorimetry. An eutectic point was found at 389°C for the composition BiI 3 : 85 mol.BiI 3 p.cent. Two new solid solutions have been discovered. Their existence has been confirmed by X-ray diffraction.

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.

Glass formation in the Ln2O2S-Ga2S3 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.

E.P.R. and a.c. susceptibility measurements results are described. For low Mn2+ content well resolved E.P.R. signals are observed at g = 2 (hyperfine interaction constant : A = 71.10−4cm−1) and poorly resolved signals at g = 4.3. For high Mn2+ content the latter vanishes, and the temperature and concentration dependence of the g = 2 signal are indicative of magnetic exchange interactions. The a.c. susceptibility exhibits a cusp around 2 K (TSG). The experiments can be interpreted by a progressive freezing of the magnetic moments, with a residual contribution of isolated Mn++ below TSG.

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 .

Extent of the glass former domain in the ternary AsGeTe system. Influence of the cooling speed on the glass formation. Correlation of the glass former ability with the phase diagram. Variation of Tg and crystallization temperatures as a function of the composition. 4 regions of glasses are characterized by their relations with the phase diagram and their thermal behaviour. A region of sub-liquidus separation of vitreous phases was observed, by annealing the glasses of lower content in tellurium; it is related to a similar phenomenon observed in the As-Te system.

Tetrahedral metastable phases are obtained by quenching from the liquid state, for n = 0.03 − 030 ( n = Cd ( Cd + Ga ) ) . These phases come back to the equilibrium state by a two steps process with two exothermic transitions. In the first step, other tetrahedral non-equilibrium phases are formed. In the second step appear the characteristic phases of the equilibrium phase diagram.

Structural and magnetic studies of the Ga 2 S 3 -rich zone of the phase diagram of the Ga 2 S 3 -Cr 2 S 3 system. The layered compound Ga 1.66 CrS 4 is isomorphous with FeGa 2 S 4 . It has a lamellar structure characterized by an alternative localization, in a host sulfur framework, of Cr, Ga and vacancies in planes perpendicular to the c axis. Each Cr 3+ ion is surrounded by six nearest S neighbours. Magnetic susceptibility versus T curve can be interpreted on the basis of a two dimensional Heisenberg model.

Two isostructural compounds are observed in the phase diagrams of the systems Ga2Te3-SnTe and Ga2Te3-PbTe. They have the general formula MGa6Te10 (M = Sn″ or Pb). They present a peritectic decomposition, at respectively 695 et 725°. The crystal structure is solved for SnGa6Te10. The rhombohedral cell, space group R32, contains 2 formulas ; a = 10.207 A, α = 89,74°. Gallium atoms are inside fully occupied tetrahedral sites. Tin atoms partially occupy, in a disordered way, 2 octahedral sites. The same structural type is observed for In2Ga6Te10, in which all the octahedral sites are filled.

From the glasses of the binary As-S system, a large region of ternary glasses is observed in the Eu-As-S system. The thermal behaviour, the magnetic susceptibility and the Raman and infrared absorption spectra show that europium is always in the divalent state, in contrast with the ternary phase diagram in which compounds of trivalent europium are present.

The crystal structure of MnSc2S4 ( a = 10.613 A , space group Fd3m) and Mn2.29Sc1.14S4 ( a = 10.523 A , space groupe Fd3m) were determined by three dimensional X-Ray diffraction. MnSc2S4 is a normal spinel structure and the atomic distribution shows that Mn2.29Sc1.14S4 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.

Preparation of glasses. Glass forming domain in the ternary system MnSGa2S3GeS2. Relations with the phase diagram. Thermal behaviour. Raman, U.V. and visible spectroscopies. Manganese has an octahedral environment of sulfur. Germanium is in tetrahedra strongly bounded to each other. The maximum concentration of manganese in these glasses is 30 at. % (Mn + Ga + Ge).

A new variety of As2Te3 is obtained by quenching the melted product, in well defined conditions of cooling. It is metastable in the solid state. It is rhombohedral, space group R3m, with a = 4.06 A c = 29.59 A . The cell contains 3 (As2Te3) sheets, where all the atoms have distorted octahedral surroundings.

Two kinds of compounds belong to this family: the compounds L 10/3 Ga 6 S 14 (L = La and Ce) and the compounds MLGa 3 S 7 and MLAl 3 S 7 (M = Ca, Sr or Eu″; L = La and in some cases Ce, Pr, Nd). All these compounds have the same tetragonal structure of the melilite type: Al or Ga cations have a tetrahedral environment of sulphur, M and L cations occupy the same 8 coordinated crystal sites. The absence of a continuous solid solution between La 10/3 Ga 6 S 14 and CaLaGa 3 S 7 could be explained by the presence of a superstructure in the last compound.