A series of n-type ZnO alloys doped with Ga and ZnS were prepared by mechanical alloying. Densities of 95% to 98% of theoretical density were achieved by hot pressing the milled powders at 1000 and 1200 degrees C, respectively. The electrical resistivity and Seebeck coefficient of alloys containing 0.25-3.0 at.% Ga were characterized between 22 and 1000 degrees C. The magnitude of the resistivity and Seebeck coefficient at 22 degrees C ranged from 0.2 m Omega cm and -25 mu V/ degrees C for the most heavily doped specimen to 1.1 m Omega cm and -70 mu V/ degrees C for the lightly doped material. The alloys exhibit a positive temperature coefficient of resistivity and Seebeck coefficient with a nearly constant slope over the temperature range studied. Thermal diffusivity measurements on a specimen containing 1.0 at.% Ga were performed over the same temperature range. The thermal conductivity appears to follow a T/sup -1/ dependence, decreasing from 180 mW/cm degrees C at 22 degrees C to 82 mW/cm degrees C at 1000 degrees C. An estimate of the maximum dimensionless thermoelectric figure of merit, ZT, in this system at 1000 degrees C gives a value of 0.26, a factor of three to four less than current state-of-the-art materials such as Si-Ge. A significant reduction in thermal conductivity would be required to make these alloys competitive with existing thermoelectric power generation materials. (9 References).
BT - Journal of Applied Physics DA - 1998/// DO - 10.1063/1.367445 IS - 11 LA - eng N2 -A series of n-type ZnO alloys doped with Ga and ZnS were prepared by mechanical alloying. Densities of 95% to 98% of theoretical density were achieved by hot pressing the milled powders at 1000 and 1200 degrees C, respectively. The electrical resistivity and Seebeck coefficient of alloys containing 0.25-3.0 at.% Ga were characterized between 22 and 1000 degrees C. The magnitude of the resistivity and Seebeck coefficient at 22 degrees C ranged from 0.2 m Omega cm and -25 mu V/ degrees C for the most heavily doped specimen to 1.1 m Omega cm and -70 mu V/ degrees C for the lightly doped material. The alloys exhibit a positive temperature coefficient of resistivity and Seebeck coefficient with a nearly constant slope over the temperature range studied. Thermal diffusivity measurements on a specimen containing 1.0 at.% Ga were performed over the same temperature range. The thermal conductivity appears to follow a T/sup -1/ dependence, decreasing from 180 mW/cm degrees C at 22 degrees C to 82 mW/cm degrees C at 1000 degrees C. An estimate of the maximum dimensionless thermoelectric figure of merit, ZT, in this system at 1000 degrees C gives a value of 0.26, a factor of three to four less than current state-of-the-art materials such as Si-Ge. A significant reduction in thermal conductivity would be required to make these alloys competitive with existing thermoelectric power generation materials. (9 References).
PY - 1998 EP - 61 EP - 5858+ T2 - Journal of Applied Physics TI - Electrical properties of Ga and ZnS doped ZnO prepared by mechanical alloying UR - http://cvining.com/system/files/articles/vining/Cook-JAP-1998.pdf VL - 83 ER -