Purity evaluation of Ta metal refined by Ar/Ar-H₂ plasma arc melting

The refining effect of Ar/Ar-H₂ plasma arc melting (PAM) was investigated and the purity of Ta metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Ta metals were removed by Ar/Ar-H₂ PAM, down to a few mass ppm levels, and the purities of respective Ta metals refined by Ar/ Ar-20 % PAM were improved up to 5N5 (99.9995 %) and 5N7 (99.99972 %). It was also found that the deoxidation reaction under hydrogen plasma condition is enhanced by a remarkable decrease in the oxygen concentration of the Ta metal refined by Ar-H₂ PAM.