Creation of heavily La-doped SrTiO3 thermoelectric films achieved by freeze-dry pulsated orifice ejection method and laser powder bed fusion

Abstract

Achieving both fine grain sizes and high doping levels simultaneously holds great promise for improving the dimensionless figure of merit (zT) of oxide thermoelectric materials; however, this remains a global challenge. This study presents a pioneering example of fabricating heavily La-doped SrTiO₃ films by leveraging the unique characteristics of laser powder bed fusion (L-PBF). A novel freeze-dry pulsated orifice ejection method (FD-POEM) was used to prepare spherical SrTiO₃–La₂O₃ composite powders with a narrow size distribution, homogeneous element distribution, and high laser absorptivity. Owing to the high processing temperature and rapid solidification of the L-PBF process, the La₂O₃ nanoparticles decomposed and dissolved in the lattice of the cubic perovskite SrTiO₃. Consequently, the thermoelectric SrTiO₃ film achieved a high La doping concentration of 36.7 mol% and a nanoscale grain size of approximately 700 nm, surpassing conventional methods. Moreover, the La-doped SrTiO₃ film, approximately 10 μm thick, was closely deposited onto a Mo substrate and exhibited excellent thermal stability at 1073 K, making it well-suited for high-temperature thermoelectric applications.