Synthesis and thermoelectric properties of boron-rich silicon borides

Boron-rich silicon borides in a boron content range 90.0 to 97.0 at% were prepared by arc-melting and spark plasma sintering. The plasma-sintered specimens consisted of SiBn when boron content over 93.7 at%, and the mixture of SiBn + SiBg when boron content below 93.7at%, while all the arc-melted specimens consisted of SiBn and free silicon. The thermoelectric properties, involving electrical conductivity, thermal conductivity as well as Seebeck coefficient were studied and the effects of the phase composition and microstructure on the thermoelectric properties were discussed. The dimensionless thermoelectric figure of merit values (Z=ct2o/K) of all the obtained silicon borides increased with increasing temperature. The plasma-sintered specimen containing 90 at% B showed the largest ZT value, which reached 0.2 at 1100 K.