Filled skutterudite compounds, YyFexCo4-xSb12(x=0-1.0, y=0-0.4), were synthesized by solid state reaction and melting methods using Co, Fe, Sb, YCl3·nH2O Powders and Y ingot as source materials. The Rietveld analysis suggests that Y3+ ions were filled in the Sb-icosahedron voids of skutterudite structure. The rattling effect of Y3+ ions filling in the voids were stronger than that of Ce3+ or La3+ ions. The lattice thermal conductivity decreased with increasing Y filling fraction, and reached the mimimum values at y=0.3. With increasing Y filling fraction, the electrical conductivity decreased and the Seebeck coefficient increased. The maximum ZT value of 0.7 at 750K was obtained for Y0.08Fe0.8Co3.2Sb12.
