We have developed a scheme for improving the thermoelectric properties of type I Ba8Ga16Ge30 clathrates by doping transition metals, TM, on the Ga sites. TM doping introduces charge distortion and lattice defects into the materials which increases the ionized impurity scattering of carriers and point defect scattering of lattice phonons, respectively; leading to enhanced power factor and reduced lattice thermal conductivity, and therefore improved ZT. ZT = 1.2 is achieved at 1000 K for Ba8Ni0.31Zn0.52Ga13.06Ge32.2. These TM-doped type I clathrates have predictable composition, tunable band gap, and therefore, offers many degrees of freedom for materials modification, design, and optimization.
Citation: Nature Materials
Pub Type: Journals
Type I clathrate, Ba8Ga16Ge30, transition metal dopants, ZT improvement