THERMOELECTRICAL PROPERTIES OF Si-Ti-B IN SITU COMPOSITE PLATES PREPARED BY CHEMICAL VAPOR DEPOSITION

ABSTRACT

Highly pure, dense SiB₄ and SiB₆ plates were prepared by chemical vapor deposition (CVD) at deposition temperatures (T_DEP) from 1323 to 1773 K, total gas pressures (P_tottot) from 4 to 40 kPa and B/Si source gas ratios (m_B/SI =2B₂H₆/SiCl₄) from 0.2 to 2.6 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 μVK⁻¹, while its electrical conductivity (s) was 7 Ω ⁻¹cm⁻¹, SiB₆ + TiB₂ and SiB₆ + SiB₄ in situ composite plates were also prepared to improve the thermoelectric property of CVD-SiB₆, The a value of the CVD-SiB₆ + 12 wt% TiB₂ in 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 SiBe + 40 wt% SiB₄ in situ composite plate (0.5 mm in thickness) was 10⁻⁵, larger than that of CVD-SiB₆