Effect of Pressure on the Resistance of Three Thallous Halides

Abstract

The effect of pressure to several hundred kilobars has been measured on TlI, TlBr, and TlCl at 25° and 120°C. Since the materials were not highly purified, the sources of conduction electrons at lower pressures, at least, are probably impurities. The resistance pressure curves show three regions. In the lowest pressure region, the resistance decreases rapidly with increasing pressure, corresponding to ionization of the impurities; in the second region the resistance depends only slightly on temperature. In this region the resistance is apparently controlled by mobility of impurities. In the third region the material appears to be a true metal. The electrical measurements are consistent with previous optical studies.