Faculté des Sciences, 40, avenue du Recteur-Pineau, 86022 Poitiers, France (Reçu le 22 novembre 1972) Résumé. 2014 Nous avons préparé par une méthode de Piper et Polich modifiée des mono cristaux cubiques de ZnSe de bonne qualité optique et qui présentent un effet électro-optique linéaire. L'étude expérimentale de cet effet a permis de constater que le coefficient électro-optique r41 du ZnSe varie avec la longueur d'onde (0,5 03BC 03BB 0,6 03BC), mais que par contre l'intensité de la modulation optique semble indépendante de 03BB et ne dépend que du champ électrique appliqué au cristal. Abstract. 2014 Cubic ZnSe crystals were grown by a modified Piper and Polich method. These crystals of good optical quality present a linear electro-optic effect. An experimental study of this effect shows that the electro-optic coefficient r41 for ZnSe varies with the wavelength (0.5 03BC 03BB 0.6 03BC), but the intensity of the optical modulation seems independent of 03BB and only depends on the electric field applied to the crystal.
ZnSe single crystals grown in vapour phase technique with sphalerite structure are cut according to faces (110), (110), (001) in order to study the coefficient γ41 of the electrooptic tensor. These samples exhibit, without any electric field applied, a parasitic birefringence linked to the plane crystal defects. This ZnSe is biaxial and presents a great dispersion of index as well as a variation of the position of the optic axes between the absorption threshold and 6000 Å, but the axis [110] remains always a principal axis for the dielectric tensor.
Calorimetric analysis shows a succession of transformations inside and outside the pores, whose characteristics depend on the concentration of the solution and the amount of porous body present.For a given porous body, whatever the initial concentration of the solution, the capillary condensate concentration evolves systematically, during cooling, towards the eutectic concentration even if the initial salt concentration is higher than the entectic one. It should be noted that this phenomenon indicates migration outside the pores of water or potassium iodide according to the initial concentration.For various samples whose pore size is decreasing, successive solidification of divided water and eutectic occurs at decreasing temperatures. The freezing temperature depression of water in divided KI solutions does not seem to be a function of the salt concentration but is dependent mainly on the division effect. A nearly linear relationship between pore radius and the reciprocal of temperature depression may experimentally be established for divided eutectic.
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