Fabrication of Non-Stoichiometric Titanium Dioxide by Spark Plasma Sintering and Its Thermoelectric Properties

Abstract

To obtain non-stoichiometric titanium dioxide, TiO₂ powder was sintered in a graphite die by spark plasma sintering (SPS). The microstructure and the crystal type of the compacts were examined. Thermoelectric properties of the compacts were measured and discussed. The results revealed that TiO₂ could be easy to be reduced in the graphite die by SPS to obtain non-stoichiometric titanium dioxide, TiO_2−x with uniform composition distribution. Electrical resistivity of the compacts decreased with increase of SPS temperature. Seebeck coefficient also decreased with increase of SPS temperature, but kept large absolute values over 300 µV·K⁻¹. Therefore, the compacts fabricated by SPS showed relatively high thermoelectric performance. The power factor reached 5 × 10⁻⁵ W m⁻¹ K⁻² at 523 K.