Modulating crystal plane orientation to enhance the ablation resistance of lanthanum-tungsten cathode for magnetoplasmadynamic thruster

The tungsten cathode of the magnetoplasmadynamic thruster (MPDT) is a critical component that determines the long-term stability of the power system. The plasma environment causes significant ablation of the tungsten cathode due to its relatively high work function. Although adding low-work-function rare earth oxides improves the cathode's anti-ablation performance, the specific influence of different processing procedures on cathode performance remains insufficiently explored. This study demonstrates that heat treatment can regulate the crystal plane orientation of liquid-liquid doped lanthanum tungsten cathode (WLa20), thus significantly enhances its anti-ablation performance. Isothermal heat treatment at 400 °C for 6 h significantly reduces steady-state ablation loss. When the heat treatment duration increases from 1 hour to 12 hours, the mass loss decreases by approximately 79.5%. Electron backscatter diffraction (EBSD) analysis shows isothermal heat treatment promotes grain orientation toward <001>, reducing blistering and ablation. Density functional theory (DFT) calculations reveal that the diagonal La configuration on the W(001) surface yields the lowest work function under an electric field, thereby enhancing both electron emission and ablation resistance. This study provides experimental and theoretical insights for designing and developing long-life cathodes for MPDT.