Abstract
The electrical conductivity, Seebeck coefficient, thermal conductivity, and figure-of-merit, which is a measure of the performance of the thermoelectric material, of heavily doped n-type PbTe single crystal and compacts of grain size in the range 10⩽
L⩽20
μm and very fine powder
L ∼1
μm, are measured in the temperature range 300–750
K. Effect of the grain size on decreasing the lattice thermal conductivity
λ
L and the total thermal conductivity
λ
t, is demonstrated. A drop of 35% in
λ
L has been achieved at 750
K for the very fine powder. Also, the figure-of-merit
Z of the very small grain size,
L∼1
μm, n-type PbTe compacts improve by 9.41% at 750
K while the large grain size material, 10⩽
L⩽20
μm, achieve 7.35% increase in
Z, at the same temperature, as compared with the single-crystal material. The result confirms that the very fine powder material is superior to large grain size or single-crystal material for thermoelectric power generation. This result is very important in the thermoelectric industry and related devices.