Study on anisotropy of n-type Mg₃Sb₂-based thermoelectric materials

The recent discovery of a high thermoelectric figure of merit (ZT) in an n-type Mg₃Sb₂-based Zintl phase triggered an intense research effort to pursue even higher ZT. Based on our previous report on Mg_3.1Nb_0.1Sb_1.5Bi_0.49Te_0.01, we report here that partial texturing in the (001) plane is achieved by double hot pressing, which is further confirmed by the rocking curves of the (002) plane. The textured samples of Mg_3.1Nb_0.1Sb_1.5Bi_0.49Te_0.01 show a much better average performance in the (00l) plane. Hall mobility is significantly improved to ∼105 cm² V^-1s^-1 at room temperature in the (00l) plane due to texturing, resulting in higher electrical conductivity, a higher power factor of ∼18 μW cm^-1K^-2 at room temperature, and also higher average ZT. This work shows that texturing is good for higher thermoelectric performance, suggesting that single crystals of n-type Mg₃Sb₂-based Zintl compounds are worth pursuing.