The calculated temperature-dependent figure-of-merit (zT ) is shown in Figure for undoped and I-doped Y 2 Te 3 . Undoped Y 2 Te 3 grown under Y-poor conditions (Figure ) has a net electron concentration of 1.1 × 10 16 cm -3 , and the low carrier concentration yields zT values < 0.1 across the entire temperature range of interest. I-doped Y 2 Te 3 under Y-rich conditions on the other hand yields an optimal electron concentration of 2 × 10 20 cm -3 (see Section 2.3) such that zT >1.0 above 1000 K.