ELECTRICAL-PROPERTIES OF SOME GLASSY COMPOSITIONS OF THE CHALCOHALIDEGE-S-I SYSTEM

dc And ac conductivities and the real part of the relative permittivit y of as-prepared and annealed bulk samples of the chalcohalide (Ge0.3S 0.7)(100-x)I-x system (0 less than or equal to x less than or equal to 20 at. %) were investigated. While the dc conductivity was measured i n the range 120 less than or equal to T less than or equal to 390 K, b oth the ac conductivity and the real part of the relative permittivity were measured in the range 313 less than or equal to T less than or e qual to 513 K, and in the frequency range from 50 kHz to 38 MHz. In th e range above room temperature, results on the dc conductivity proved semiconducting behaviour for the considered compositions. Thus, the ac tivation energy could be calculated. Besides, in the range below room temperature, the results for de conductivity were used to calculate th e values of the density of localized states at the Fermi level. Both t he real part of the relative permittivity and ac conductivity showed w eak thermal activation. Besides, results of the frequency dependence o f ac electrical conductivity at different temepratures gave the predic tion that the quantum mechanical tunneling model is the most suitable to describe the ac conduction behaviour in different compositions of t he present system.