A possible direction of semiconductor research is the search for novel materials of appropriate properties for different applications. One of the important groups of such semiconductor compounds is the chalcogenides. Well-known examples of binary compounds of this group are CdSe, CdS, CdTe, ZnSe, ZnS, ZnTe, etc. They are good photoconductors and have high absorption coefficient; therefore they have practical application in solar cells, in photosensors and in other optoelectronic devices. Material properties can be improved and modified by forming ternary, quaternary etc. compounds of the above.

Let us take for example CdS and CdSe which are unstable in acidic media and corrode easily. However ternary chalcogenid materials such as Cd4GeSe6 and Cd4GeS6

The synthesis of Cd4GeSe6 crystal was carried out from

chalcogenide (CdSe) and dichalcogenide (GeSe2) sources. The powdered source materials were well mixed in a silica ampoule 22 mm of diameter and 150 mm of length. The Cd4GeSe6 material was synthesised during a two day annealing at 1120 K. After the synthesis crystals were produced by chemical vapour transport technique. The transport agent was iodine. The starting material was kept at 830 K. The deposition zone for crystallisation

was 750 K. The crystallising period ranged from two to three weeks. The obtained crystal size was about 10x5x4 mm3. The obtained Cd4GeSe6 pieces are dark grey and are glistening, poly — and monocrystalline. The identification of the crystal was carried out by X-ray diffraction and the obtained data correspond with the literature values. The parameters are the follows: a = 12.937 A, b = 7.402 A, c = 12.852 A and у = 110.9 °. The thermal stability of the crystal was investigated by differential thermal analysis and thermogravimetry measurements. The thermogravimetry investigations showed that the loss of weight was only 1.9 % until 740 K and was no differential thermal analysis effect during this period, too. Therefore we concluded that Cd4GeSe6 is a stable crystal and keeps its stability even at high temperatures under normal atmospheric conditions.