Microstructures and thermoelectric properties of (FeSb/sub 3/)/sub 1-x/La/sub x/ ribbons

The microstructures and thermoelectric properties of the spin-cast (FeSb/sub 3/)/sub 1-x/La/sub x/ (x=0-0.4) ribbons were investigated by means of X-ray diffraction measurements, transmission electron microscopic observations, EDX analyses, measurements of the electrical resistivity and thermoelectromotive force. The ribbons consist of various structures : FeSb/sub 2/+Sb for x=0, LaFe/sub 4/Sb/sub 12/+FeSb/sub 2/+Sb for x=0.1, LaFe/sub 4/Sb/sub 12/ for x=0.2, LaFe/sub 4/Sb/sub 12/+La/sub 2/Sb+LaSb+LaSb/sub 2/+FeSb for x=0.3 and 0.4, where LaFe/sub 4/Sb/sub 12/ is the filled skutterudite structure. A precipitation zone appeared along the grain boundaries of LaFe/sub 4/Sb/sub 12/ for x>0.2, while it was not seen for x<0.2. As the amount of LaFe/sub 4/Sb/sub 12/ decreases with deviation from x=0.2, the electrical resistivity decreases more rapidly for x>0.2 than for x<0.2. The Seebeck coefficient is large between x=0.2 and 0.3. The large power factor is obtained between x=0.2 and 0.3, being the high value of 20 /spl mu/W/cmK/sup 2/ at 350 K and 50 /spl mu/W/cmK/sup 2/ at 550 K.