The electrical conduction in a double-phase system

Depending on the fractional volumes of the amorphous (a) and the crystalline (c) phases, a series of compressed powder samples of a double-phase selenium mixture were prepared and the dc properties of the samples have been measured and discussed. The activation energy of conduction decreases from 1.8 eV (for the sample of 90% a and 10% c) to 0.67 eV (for 10% a and 90% c). For the same range of the fractional volumes, the conductivity of the mixture σsub(m) at room temperature increases from approx. 10-13 ohm-1 cm-1 to 10-7 ohm-1 cm-1, and the pre-exponent factor C of the Arrhenius conductivity equation increases from approx. 10-4 ohm-1 cm-1 to approx. 3 ohm-1 cm-1. An empirical equation has been found to fit the measured conductivity data in the whole range of the double-phase system. Moreover, this formula has been tested for massive selenium samples of different known degrees of crystallinity, defined from X-ray measurements, and very satisfactory results are found