Volume 8 Issue 2 ( June 2021 )


Rapid Synthesis of W18O49 via Reactive Spark Plasma Sintering with Controlled Anisotropic Thermoelectric Properties

Nhat Quang Minh Tran, Michitaka Ohtaki, and Koichiro Suekuni


Single phase W18O49 sintered polycrystalline samples were successfully synthesized via one-step rapid reactive spark plasma sintering directly from commercially purchased WO3 and WO2 powders. Thermoelectric properties of the samples sintered at 15 and 30 MPa showed insignificant anisotropy, while a strong anisotropy was observed for the sample sintered at 50 MPa. The in-situ reaction under a high applied pressure allowed a preferential grain growth along the direction perpendicular to the pressure axis. The high anisotropy of the sample sintered at 50 MPa yielded the lowest thermal conductivity of 4 Wm-1K-1, resulting in a ZT value of 0.08 at 1073 K. This study offers the rapid and cost-effective preparation method for W18O49 materials, which can also be applied for other tungsten suboxide phases, with partially controlled anisotropic properties by the influence of applied pressure for thermoelectric performance enhancement.

Keywords: oxide thermoelectrics, lattice thermal conductivity, reactive spark plasma sintering, pressure-induced anisotropy, transition metal oxides