Sustainable and homogeneous arc ablation behavior of zirconium cathodes improved by in situ formation of zirconium oxides

Discharge homogeneity is one of the dominant factors affecting cathode lifetime. In this work, the arc ablation behavior of a zirconium cathode is investigated in air and argon atmospheres. Homogeneous discharge processes are observed in air, while poor discharge homogeneity with scattered cathode spots is found in argon. The homogeneous discharge process is related to the layered structure at the discharge center. The surface zirconium oxide layer stabilizes the arc foot and reduces the effective work function. A dual-phase layer underneath, consisting of zirconium oxides and zirconium, enables the transition from the zirconium matrix to the surface oxide layer. The sustainable discharge behaviors are realized by the balance in the cathode, which is created by the ablation of surface zirconium oxides and the oxidization of zirconium in the dual-phase layer.