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A3: High temperature materials
Zintl phases are ideal candidates for high efficient thermoelectric materials since they are typically small-band gap semiconductors possessing complex crystal structures. Structural complexity leads to extremely low lattice thermal conductivity due to confinement of heat in low velocity, optical phonon modes, as well as additional opportunities for scattering events. Indeed, among bulk materials, Zintl compounds exhibit some of the lowest reported lattice thermal conductivities. In addition, such phases allow fine tuning of carrier concentration without disrupting electronic mobility, which is essential for optimizing thermoelectric efficiency. Herein, we will present the preparation, chemical characterization and the thermoelectric properties of several Zintl phases in the systems Ba-Zn-Sn and Ba-Ga-Sb.