Preparation of high purity tellurium by zone refining

This paper describes purification process of tellurium metal using zone refining technique under high purity hydrogen gas ambient in normal room environment. Process automation by newly designed stepper motor drive and allied process control instruments circumvent the complexity of electrical motors. It is observed that overall impurities have gone down substantially from 4N+ to 5N5 purity with reference to Fe, Mg, AI, Cr, Zn, Bi and Cu. Removal of selenium is effected by hydrogen, which also serves as carrier gas during zone refining. The selenium in tellurium matrix is found to be below detection limits. The zone temperature, zone length and tilt angle maintained in the experiment are adequate to go down to high purity levels.