Preparation and Purity Evaluation of 5N-Grade Ruthenium by Electron Beam Melting

Abstract

In this study, we carried out an electron beam (EB) melting purification process to obtain a 5N-grade high-purity Ru ingot from commercial Ru powder. The first step was to primarily sinter Ru powder compact by means of vacuum heat treatment at 1,773 K. Vacuum sintering was employed to ensure a high vacuum condition during EB melting by the removal of remaining gaseous elements between the compact powders. The second step was to obtain Ru ingots by EB melting of the sintered Ru compact. The purity of the Ru raw powder was 99.962 mass% and the purity of a premelted Ru button ingot obtained by EB melting was 99.9873 mass%. The purities of the respective Ru button ingots remelted for 2 and 4 min were 99.9988 and 99.9992 mass%, respectively. As a result, the sum of metallic impurities in the Ru ingot refined for 6 min was 5.3 mass ppm and the purity of the ingot considerably increased up to 99.9995 mass%, which means that a 5N-grade high-purity Ru ingot can be obtained by the EB melting purification process. Furthermore, the EB-melted Ru ingot showed an excellent ability to remove interstitial impurities.