Thermoelectrical properties of Si-Ti-B in situ composite plates prepared by chemical vapor deposition

Highly pure, dense SiB4 and SiB6 plates were prepared by chemical vapor deposition (CVD) at deposition temperatures (Tdep) from 1323 to 1773 K, total gas pressures (Ptot) from 4 to 40 kPa and B/Si source gas ratios (mB/Si=2B2H6/SiCI4) from 0.2 to 2.8, and their thermoelectrical properties were measured. The Seebeck coefficient (S) of CVD-SiB6 (0.7 mm in thickness), which is known to be a high temperature thermoelectric material, was 320 μVK1, while its electrical conductivity (s) was 7 Q-1cm-1, SiB6 + TiB2 and SiB6 + SiB4in situ composite plates were also prepared to improve the thermoelectric property of CVD-SiB6. The σ value of the CVD-SiB6 + 12 wt% TiB2in situ composite plate (0.7 mm in thickness) was one order of magnitude larger than that of CVD-SiB6 at room temperature, while the figure of merit for the thermoelectric materials (Z) was smaller because of the smaller value of S. However, the Z value of SiB6 + 40 wt% SiB4in situ composite plate (0.5 mm in thickness) was 10-5, larger than that of CVD-SiB6.