A promising layered thermoelectric metallic ceramic with ultra-high temperature stability: Mo2Ti2AlC3

Abstract

As a structural ceramic, MAX phases have attracted the most attentions because of light weight, excellent machinability, good thermal shock resistance and thermal stability at ultra-high temperature. Herein, for the first time we reported the thermoelectric property of Mo2Ti2AlC3, one of MAX phases. It has similar resistivity (~2.3 μΩ·m) and higher Seebeck coefficient (−15μV/K) compared with Pt-Rh alloy. Mo2Ti2AlC3 has higher power factor (~46% improvement) and much lower thermal conductivity (6.2 W/(m·K), one-third) compared with SiC thermoelectric ceramics at 700 °C. The ZT value is about 0.0138 at 700 °C, which is three times as high as that of SiC-7%Si3N4 thermoelectric composite. These suggest that Mo2Ti2AlC3 and other MAX phases have an important application prospect in the field of thermoelectric generator and temperature sensor at ultra-high temperature. Meanwhile, although Mo2Ti2AlC3 ceramic shows metallic transport behavior, the electric thermal conductivity far deviates from traditional Wiedemann-Franz law, indicating that there are strong correlations or couplings between electrons and 2-D layered lattices, and Mo2Ti2AlC3 is a new strong related system with spin-orbital coupling.