(630f) Combustion Synthesis of Thermoelectric Oxide Powders

Doped calcium cobaltate powders were prepared by Self-propagating High-temperature Synthesis (SHS).  Reactant powders are consolidated to a pellet and ignited by an external heat source.  The heat released from the reaction is sufficient to sustain the movement of the reaction front to convert the reactants into the product.  TG-DSC analysis was performed to establish the reaction mechanism.  Thermocouples and an IR camera were used to measure the temperature history at the pellet centerline and pellet surface during the combustion to determine the velocity of combustion front movement.  Products were characterized by XRD for phase purity.  Synthesized powders were hot-pressed to form dense pellets and characterized for their thermoelectric properties.  Our results show that SHS can economically produce thermoelectric oxides with high ZT values and the thermal conductivity of calcium cobaltate decreases when silver is doped to replace calcium.