Thermoelectric power of ionic crystals—V. Thermoelectric power of potassium bromide and sodium bromide using bromine gas electrodes

• Published in: The Journal of physics and chemistry of solids 1970-07, Vol.31 (7), p.1553-1563
• Main Authors: Hoshino, Hideoki, Shimoji, Mitsuo
• Format: Article
• Language: English
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/0022-3697(70)90040-5

The thermoelectric powers of single crystals of KBr and NaBr, undoped and doped with BaBr 2, were measured as a function of temperature between 400–540°C using bromine gas electrodes. Slight discolouration of the crystals, observed after the thermoelectric power measurements, suggests that stoichiometric excess of bromine presumably yield cation vacancies and holes. The transport numbers of the holes can be neglected under the experimental condition of interest, as inferred from Mollwo's work. The experimental results of the thermoelectric power are interpreted in terms of theoretical expressions for homogeneous and heterogeneous thermoelectric power. The values of heats of transport of both cation- and anion vacancies are in agreement with those of heats of activation for migration of respective ions, as predicted from the non-equilibrium theory based upon the Fokker-Planck equation (papers I and III of this series). It is quantitatively shown that the heterogeneous thermoelectric powers of the KBr and NaBr crystals being in contact with the inert metal electrodes may depend on the electrode materials and on the purity of the crystals.