Thermoelectric properties of boron and boron phosphide CVD wafers

The electrical conductivity of amorphous boron wafers obeys Mott's T/sup -1/4/ rule. BP and B/sub 12/P/sub 2/ show band conduction. The thermoelectric power of polycrystalline B decreases with increasing temperature, while that of amorphous B is almost constant in a wide temperature range. That of BP increases with increasing temperature and becomes constant between 600 and 1100 K, while that of B/sub 12/P/sub 2/ shows a high value of 800-1000 /spl mu/ V/K at 400-800 K. The weak temperature dependences of thermal conductivities of BP and B/sub 12/P/sub 2/ polycrystalline wafers reflect phonon scattering by grain boundaries while that of amorphous boron is almost constant in a wide temperature range, showing a characteristic of a glass. The figure of merit for polycrystalline BP is 10/sup -7//K at high temperatures while that of amorphous B is 10/sup -5//K, being promising for thermoelectric devices. Low electrical conductivity of B/sub 12/P/sub 2/ produces a lower thermoelectric figure of merit than BP by two orders of magnitude, despite the high thermoelectric power.