Thermoelectric Properties of Nb-Doped SrTiO3/TiO2 Eutectic Solids Fabricated by Unidirectional Solidification.

Undoped and Nb-doped SrTiO₃/TiO₂ (STO/TO) eutectic solids were fabricated from the melt at a eutectic point of STO and TO by unidirectional solidification. Fabricated undoped and Nb:STO/TO eutectic solids were composed of the TiO₂ rod-like and the SrTiO₃ matrix phases, and the periodic and uniform eutectic morphology could be achieved in the Nb:STO/TO eutectic solids by stable control of the liquid-solid interface during the fabrication. The thermal conductivity of the Nb:STO/TO eutectic solid was less than half of that of the Nb:STO single crystal owing to the decrease of the lattice thermal conductivity by phonon scattering at the grain boundaries. The figures of merit ZT's of the Nb:STO/TO eutectic solid, parallel and perpendicular to the growth direction, were ∼ 0.007 and ∼ 0.0004, respectively. The small ZT's are attributable to the higher electrical resistivity originating from the insufficient carrier doping and high electrical resistivity of the TO phase. [ABSTRACT FROM AUTHOR]