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 − y Yb y Te 4 . This allows the substitution of divalent Yb to be utilized to optimize the thermoelectric performance in lanthanum telluride. The addition of Yb 2+ 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 Yb 2+ for La 3+ results in a threefold finer control over the carrier density n, thus allowing the optimum n ∼ 0.3 × 10 21 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.