Some thermoelectric properties of the light rare earth sesquiselenides (R2Se/sub 3-x/)

Rare earth sesquiselenides of the Th3P4 structure show variable electric properties over their homogeneity range, i.e., ranging from metallic (R3Se4) to semimetallic (R2Se/sub 3-x/, where 0.14 > x > 0) to semiconducting (R2Se3). The composition change is due to the formation of metal vacancies in the Th3P4 structure with no vacancies at R3Se4 and 4.75 at. % vacancies at R2Se3. The rare earth sesquiselenides are also refractory materials and therefore are of interest for high temperature thermoelectric applications. Preliminary results of thermoelectric power and electrical resistivity measurements on the light lanthanide sesquiselenides (La through Sm) are presented