Electrical Properties of Liquid Selenium I

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Abstract
The thermoelectric power of liquid selenium has been measured in the range 250–500°C. Values of activation energies calculated from the temperature dependences of thermoelectric powers and resistivities agree. This activation energy taken as the intrinsic activation energy (or the energy to break the Se–Se bond) is 2.31 ev calculated from data given by Henkels. The mobility of holes in the intrinsic region exceeds that of electrons and has a value (8.4×106)/T32 cm2/volt sec, assuming electronic mass. As a further check of the electronic nature of the conduction in the liquid and of theories of conduction in the hexagonal form, preliminary measurements of the thermoelectric power of pure selenium doped with small percentages of As, Sb, and Bi up to 4 percent were made. In the intrinsic region the specimens exhibited p type conduction, but at lower temperatures the sign of the thermoelectric powers reversed and values became quite large but negative. The crossover point depended qualitatively on the amount of impurity in the correct manner. The n type conduction is tentatively attributed to donor levels introduced by the normal trivalence of Group Vb elements. Two p electrons are considered bound in the selenium chain, the third ionized at high temperature.

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