Abstract With the guidance of density functional theory (DFT), a high‐performance hafnium (Hf) cathode for an air/water vapor plasma torch is designed and the concepts and principles for high performance are elucidated. A quasi‐nanocrystalline hexagonal close‐packed (HCP) Hf–La 2 O 3 cathode based on these design principles is successfully fabricated via a powder metallurgy route. Under identical voltage and temperature conditions, the thermal emission current density of this quasi‐nanocrystalline Hf–La 2 O 3 cathode is ≈20 times greater than that of conventional Hf cathodes. Additionally, its cathodic lifespan is significantly extended. Quasi‐nanocrystalline Hf–La 2 O 3 products are manufactured into cathode devices with standard dimensions. This fabrication process is straightforward, requires minimal doped oxides, and is cost‐effective. Consequently, the approach offers substantial performance enhancements over traditional Hf melting methods without incurring significantly additional costs.

DFT Guided Design and Preparation of Quasi‐Nanocrystalline Hf–La2O3 Cathode with Unprecedented Thermal Emission Performance