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Studies of several glasses in the system As2SexTe3-x have been made by differential thermal analysis (DTA). Observations were made of the glass transition point (T 1, the temperature of crystallisation and the temperature of melting. g Glassy material of the following seven compositions was prepared -As Se 4 6 (i. e. As2Seg), As Se Te, As4Se4Te2, As4Se3Te3, As4Se2Te4, As4SeTe5, and As4Te6 (approximately 10 g of each co,pposition) in sealed, evacuated silica tubes.The silica tubes were heated either at '800 O C (A) or at 600 O C (B) for about 3 h.Henceforth the materials will be denoted A or B depending on which of the above temperatures was used. Samples of the first three compositions, As Se and As4Se4Te2 in their tubes were taken out of the furnace and allowed to cool naturally in a i r to room temperature in about 5 min. The other materials (in their tubes) were quenched in water. These differences in the cooling procedure a r e associated with the fact that in the system As2SexTe3-x an increase in the tellurium content results in a much stronger tendency to crystallisation. In the case of As4Te6(A) only a small detached part of the ingot was glassy after quenching but this part was big enough to use in a DTA experiment. Finally we should record that it became desirable to produce crystalline samples (C) of As4Se6, As4Se5Te, andAs Se Te and that this was done by long periods of annealing at the most suitable temperature for each material. 4 5 As4Se5Te, 4 6' 4 4 2 The apparatus used for the DTA was a Standata Model 6-25. The normal experimental procedure in the DTA was to a) raise the furnace temperature slowly, i.e. at about 4 deg/min,to about 600 C, b) lower the temperature at the natural cooling rate of the furnace, i.e. at an aver-0 age rate of about 1.5 deg/min, to 100 OC, 0 c) raise the temperature again to 600 C, and d) lower the temperature to 20 C.In all cases the DTA sample tube was filled for the initial run a) with material which 0 4 4 2 0 material in vacuum for 10 h , in one case a t 265 C producing As Se T e (C) and in a second case at 290 O C producing material which will be denoted As Se T e (D). W e made a DTA run for As Se T e (C) with rising temperature which showed one melting peak (P) and a similar run for As Se T e (D) which showed two peaks (Q and R); P and Q correspond to the same temperature ( Fig.

Heat treatment of bulk gallium arsenide using a phosphosilicate glass cap Radiative transitions induced in gallium arsenide by modest heat treatment

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