Activation Seebeck effect

In 1948 Verwey and his co-workers (88) established that lithium ions incorporated into nickel oxide produced an equivalent number of Ni + ions and so enhanced the electrical conductivity. Later, from measurements of the Seebeck effect, Parravano (89) confirmed that in the presence of lithium the Fermi level of nickel oxide is indeed depressed in accordance with the increased concentration of positive holes. For trivalent additions, Hauffe and Block (90) have shown that the incorporation of small amounts of Cr + ions decreases the conductivity of nickel oxide one infers accordingly that the hole concentration is decreased and that the Fermi level is raised. This is therefore an attractive situation with which to examine the influence of the height of the Fermi level on catalytic activity. The most appropriate n-type oxide for analogous studies is zinc oxide. 

Hakim investigated the electrical properties of In203 and ITO films prepared by spray pyrolysis by measuring the electrical resistivity as a function of temperature [100], the Hall effect and the thermoelectric power [99]. He observed a very complicated dependency of the electrical resistivity on the temperature with an activation energy of about 0.07-0.1 eV for the temperature range of 70-190°C. These low values indicate shallow donor levels [124]. The Seebeck coefficients or the thermoelectric power of ITO films were in the range of 16 to 200 pV K . 

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