Au and B co-doped p-type Si-Ge nanocomposites possessing ZT = 1.63 synthesized by ball milling and low-temperature sintering

Abstract

The enhanced value of the dimensionless figure of merit was achieved in a P-type Si-Ge alloy containing a small amount of Au and B, Si0.62Ge0.31B0.03Au0.04. After the 6 h ball milling, the sample was sintered at 873 K under 400 MPa with a soaking time of 4 h. The precipitation of (Au) occurred in Si-Ge alloy matrix. The large Seebeck coefficient of 464 μVK-1 was achieved at 973 K, which might be due to the sharp peak, that consists mainly of 5d states of Au, near the top of the valence band in the electronic density of states. Assisted by the values of electrical resistivity ∼10 mΩcm and thermal conductivity 1.5 Wm-1 K-1, the large Seebeck coefficient led to a value of ZT exceeding 1.6, which is much higher than that of previously reported Si-Ge-based composites.