Year: 1970
Type: article
Abstract: In a polycrystalline material such as the compacted natural graphite flake used in this study, the electronic transport properties of greatest interest are the absolute thermoelectric power (since it is relatively independent of crystalline size and shows the effect of the individual Fermi surfaces), its temperature dependency and the Hall constant. Studies on the undoped compacts in the temperature range 77-550°K show that the absolute thermoelectric power decreases with increasing temperature, passing from positive to negative values at about 250°K. The room temperature value (α300) is-1.5μV/°K.In our work, boron powder was mixed with SP-1 graphite, compacted and annealed to give final B/C atom ratios of -10-6, 10-5, and 5×10-4, 1, 2 and 5×10-3 and 10-2 (1%). The effect of boron on α and its temperature dependence is quite marked, shifting d300 to a positive peak of 20 μV/°K at a B/C ratio of 10-3. There is a strong correlation of the change in behavior of α and Ro vs boronation at a Fermi level shift of 0.02 eV and a B/C atom ratio of -2×10-4, indicating boron's high ionization efficiency. Except at high boron concentrations, these changes are not accompanied by any marked change in the resistivity.
Source: TANSO
Authors: P.S. Grosewald, P.L. Walker
Institution: Pennsylvania State University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
Funder: Battelle
OpenAlex ID: W2130513267