Profiling of selenium removal in hydrogen ambient zone-refined tellurium bar using RF-GDOES

Ultrapure tellurium (Te) metal has become an important metal in the strategic sector for fabricating high performance infrared devices for thermal imaging and night vision cameras. Zone refining (ZR) is a proven technique for purification of Te. Selenium (Se), present as an impurity in Te, is not easily removed by ZR under normal conditions as the segregation coefficient (K) is around 0.44-0.50. Hence, ZR was performed in a hydrogen atmosphere, during which Se gets converted to hydrogen selenide at the molten moving zones and carried away into the sodium hydroxide scrubbers. In this study a radio-frequency glow discharge optical emission spectrometer (RF-GDOES) was used for determining the concentration of Se along the 56 cm Te zone-refined bar. It was observed that the initial concentration of 1100 ppb Se was decreased to 30 ppb after 2 cycles.