Nitridation of a Ti–V Metal Pair and Evaluation of the Thermoelectric Power of the Resultant Ceramic

Abstract

Ceramic nitride samples of tailored composition and shape have been prepared by controlled nitridation of Ti–V metal pairs. We have obtained kinetic and current–voltage curves for the interaction of the Ti–V metal pairs with nitrogen. In different parts of the metal pairs, the nitridation process follows different mechanisms. In the case of the pure metals, the formation of nearly stoichiometric ceramics involves the formation of three- and two-layer graded structures. Nitridation of the junction region, containing a Ti–V solid solution, is determined by the chemical affinity of titanium and vanadium for nitrogen. The formation of titanium nitride leads to decomposition of the Ti–V solid solution in the junction and vanadium metal separation on grain boundaries. The rate of vanadium nitridation increases as the titanium content of the solid solution decreases. The thermoelectric voltage of the Ti–V system in the temperature range from –195.7 to +550°C has been evaluated as a function of the degree of nitridation. The thermoelectric voltage and Seebeck coefficient of metal–ceramic and ceramic structures have been determined as functions of temperature. Characteristically, the thermoelectric voltage of all the nitrided pairs rises monotonically over the entire temperature range studied. Nitrided titanium–vanadium pairs with tailored composition can be used as ceramic thermoelectric converters.