Thermoelectric Behavior of Solid Particulate Systems. Nickel Oxide

Abstract

Thermoelectric power measurements have been performed on powdered nickel oxide in the temperature range 60–220°C, under different gas atmospheres. These include: oxygen, hydrogen, carbon monoxide, carbon dioxide, nitrous oxide, helium, and water vapor, at different partial pressures. The extent and direction of the observed changes in thermoelectric power of the oxide following gas chemisorption have been related to the extent and nature of the electron transfer process taking place between the different gaseous molecules and the conducting surface. A theoretical analysis of the system is presented. The analysis shows how the ratio between the thickness of the space charge layer at the surface and the ``thickness'' of the thermal gradient affects the thermoelectric power change resulting from chemisorption. Since this ratio depends on the size and size distribution of the solid particles, this effect provides a further parameter which can be used to control and modify the electronic characteristics of semiconducting particulate systems.