Experimental investigation of phase relations in Bi-Te-RE (Yb, La, Ce) ternary systems

Rare earth (RE) elements especially Yb, La and Ce have been frequently doped to Bi-Te alloys to improve thermoelectric performance. Three isothermal sections: Bi-Te-Yb at 573 K, Bi-Te-La and Bi-Te-Ce at 673 K were partly established by means of electron probe micro-analysis (EPMA) and powder X-ray diffractometry (XRD). The determined maximum solubilities of RE elements in Bi-Te alloys are very small and that of Yb reached the maximum about 0.3 at% at 573 K. Both LaTe2 and CeTe2 can dissolve a large amount of Bi, about 10 and 13 at% at 673 K, respectively. No ternary compound has been confirmed.