Purification of tellurium to nearly 7N purity

Vacuum distillation and zone melting purification processes of tellurium were studied. Results were obtained by atomic absorption spectroscopy with graphite furnace (AASGF). Concentrations of impurities such as Al, Ag, As, Ca, Cu Fe, In, Mg, Mn, Na, Pb, Se, Pd, and V were successfully decreased. We confirmed that the ultimate distribution of impurities was reached. A series of segregation coefficients was determined by fitting the experimental measurements of concentrations with Pfannʹs model plots. The majority of segregation coefficient values were less than 1. The segregation process and diffusion coefficients were affected by the atomic dimensions of impurities. Global characterization of the grown tellurium purity was achieved by electrical measurement on samples of tellurium at liquid helium temperature. We observed an increase of the electric mobility as well as a decrease in the number of carriers.