Thermoelectric nanocomposite from the metastable void filling in caged skutterudite

摘要

We report a novel approach to realize the formation of well-distributed nanodispersions in n-type filled skutterudite through the manipulation of metastable void fillers by a designed sophisticated process of materials synthesis. Metastable Ga filling in CoSb_3 is proved to happen at high temperature. The subsequent controlled annealing procedure drives Ga out of the crystal voids and finally leads to the homogeneous dispersion of GaSb nanodots with an average size of 11 nm in CoSb_3 matrix. The grain size of nanodispersions can be manipulated by the controlled cooling procedure. The well-distributed nanodispersions are observed to enhance Seebeck coefficients and reduce lattice thermal conductivity at low temperature. Therefore, the thermoelectric performance of nanocomposite is improved in the whole temperature range. The highest figure of merit (Z7) is obtained to be 1.45 at 850 K, and an average ZT of 0.99 in 300-850 K is achieved for Yb_(0.26)Co_4Sb_(12)/ 0.2GaSb nanocomposite.