ANNIHILATION OF POSITRONS IN CRYSTALLINE AND GLASSY Tl-Ge-Te AND Tl-Si-Te MATERIALS.

The angular distribution curves were determined for the photons resulting from the annihilation of positrons in some crystalline and glassy materials belonging to the ternary Tl-Ge-Te and Tl-Si-Te chalcogenide systems. The angular distributions were analyzed using the parameter f equals I(O)/O(8) representing the fraction of the positrons annihilated at defects, where I(0) and I(8) are the counting rates at the maximum and at an angle of 8 mrad on the distribution curve. The momentum distribution of the annihilating electron-positron pairs was deduced from the angular distributions of the photons. The results were used to obtain information on changes in the defect structure of the materials resulting from the glass-crystal transition.