Reprocessing Leading to Lower Thermal Conductivity of ZnO Thermoelectrics

Nanometer sized ZnO powder was co-doped with gamma aluminum oxide and gallium oxide and
sintered using a direct current sintering furnace. Sintered samples were reprocessed by crushing the
samples in a Carver press, then milling for 4 hours. The reprocessed samples were then re-sintered in
the direct current sintering furnace. Heat capacity, density and thermal diffusivity were measured in
order to determine thermal conductivity as a function of temperature. Thermoelectric properties were
measured. It was found that the thermal conductivity decreased from 7 W/m K to 3.5 W/m K at 805K
by using the reprocessing technique. It is projected that the value will be less than 2 W/m K and the
figure of merit greater than 0.65 at 1400K.