Optimizing thermoelectric efficiency in La_3-xTe₄ via Yb substitution

A low temperature, solid state synthesis technique has enabled the production of homogeneous samples of La_3-x-yYb_yTe ₄. This allows the substitution of divalent Yb to be utilized to optimize the thermoelectric performance in lanthanum telluride. The addition of Yb²⁺ changes the electrical transport properties in a manner that can be well understood using valence counting rules and a corresponding change in the Fermi energy. The substitution of Yb²⁺ for La³⁺ results in a threefold finer control over the carrier density n, thus allowing the optimum n ∼ 0.3 × - 10²¹ cm^-3 to be both predicted and prepared. The net result is an improvement in thermoelectric efficiency, with zT reaching ∼ 1.2 at 1273 K.