Heat Effects of Electron Beam Melting on Impurity Distribution—High Purity Zirconium Ingot

High purity Zirconium ingot is the fundamental material for Zirconium sputtering targets used in the Physical Vapor Deposition (PVD) process. Zirconium oxide (ZrO₂) shows high permittivity when structured as thin layers. The high purity of the sputtering target is essential to ensure the electrical conductivity and permittivity of the thin films in devices. To achieve high purity in the sputtering target, the Electron Beam Melting (EBM) process has been applied to purify high-melting-point metals such as Titanium and Molybdenum. Previous studies focused on the interaction among metals and Oxygen and Nitrogen, suggesting conditions for removing components based on partial pressure. To enhance the purification process using EBM, the behavior of impurities by electron beam should be studied from various perspectives. In this study, the Electron Beam Melting (EBM) refining process for Zirconium was conducted under various electron beam power conditions. The calculation of the phase diagram was considered at the point of interaction between the metal and impurities. The separation factor of impurities was derived from the activity and partial pressure of the components to predict the tendency for impurity removal. To predict heat transfer and flow during the EBM process, the Finite Element Analysis (FEA) was performed, using several electron beam parameters assumed. The EBM refining process was applied to an on-grade Zirconium sponge under beam power from 14kW to 21kW. To verify the removal of impurities, ICP-OES was conducted on each section of the ingot. The distribution of impurities and the microstructure were analyzed by SEM, EDS, EPMA, EBSD, and XRD. The effects on impurity distribution were discussed based on the heat transfer and accompanying solidification from the EBM.