There is a number of cases where chalcogenic glass semiconductors have to be practically used as optical materials. Therefore, their transparence characteristics have to include both the visible and close infrared part of the spectrum, particularly the wavelengths of He-Ne (0.6328#m) and CO2 (10.6#m) lasers. Analysing the literature data [1,2] it was possible to find out that there are only a few glass compositions from binary As-S systems which are vitrous at 0.63 and 10.6 #m. However, thermodynamic parameters and conditions under which these materials are synthesized prevent the formation of optically homogeneous glasses of greater dimensions with predetermined physical chemistry and optical characteristics. Therefore, in order to obtain more favourable technological characteristics of glass, other components are added, first of all germanium and antimony. It has been found that glasses from the Ge-As-S system are characterized by the large value of the coefficient of linear expansion, while those from Sb-As-S system are characterized by the significant tendency of crystallization which also prevents synthesis of optically homogeneous glasses of greater dimensions.Systematic investigations of the processes of glass formation, chemical interactions and formation of glass structures in the complex M-AV-BVI-c w~ systems (where M is an arbitrary element from the Periodic Table of Elements AV-p, As, Sb, Bi; BvI-S, Se, Te; CVU-C1, Br, I) have indicated the system Ge-As-S-I as the most optimal one from the physico-technological point of view. The combination of the Ge20ASl4Ss2Ii4 type proved to be particularly optimal [3]; even sulphur is replaced by selenium. After this substitution the energy gap calculated from electrical measurements is changed by more than 0.40 eV.In order to investigate the general physicaltechnology characteristics and the possibilities of obtaining the materials with a pre-determined energy gap on the basis of sulphur and selenium content variation, five-component samples of the Ge20As14(SexSl_~)52Ii4 type were synthesized.

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The effect of adding iodine to the binary systems As.Se on the thermal stability of the ternary glasses thus formed was investigated by DTA and DDTA. The investigated glasses corresponded to different regions of the phase diagram, i.e. they had different contents of As and I and, consequently, contained different types of structural units.In the investigated ternary systems with iodine, the crystallization effect appears at a lower temperature than in the binary glass As40Se60, and the same holds for the temperatures of softening and melting.For both binary and ternary systems, the activation energies of crystallization were determined. The glass As40Se~o exhibited a somewhat higher activation energy, i.e. a somewhat lower tendency to crystallize than the ternary system.The critical cooling rates of the melts for minimum degree of crystallinity were estimated. The obtained values are approximately equal for the binary (As2S03) and ternary (AsSeI) systems.Studies of general physical properties of the binary system As-Se and the ternary system As-Se-I, and determination of the short wavelength limit, other optical properties and their microhardness, have recently been reported [1][2][3][4].With the use of Raman spectroscopy, it was established that the As-Se-I glasses with an As content below 2 at% and an I content below 10 at% consist of Sen chains and Se8 rings, and of AsI3 structural units statistically distributed between them.In a second group of glasses, corresponding to 2

A review is given of glass synthesis including the discussion of the area of glass formation in the quaternary GeAsSI system. Analyses of the probable glass structure are carried out according to the vibration spectra. The results obtained indicate that this system may be treated as quasibinary combination of (AsSI) x (GeS2)1−x type.