Microstructure of ZrNiSn-base Half-Heusler Thermoelectric Materials Prepared by Melt-spinning

Thermoelectric materials Zr(Hf)NiSn(Sb) alloys were prepared by levitation melting followed by melt- spinning to refine the microstructure, and then consolidated by spark plasma sintering for the property measurements. XRD analysis showed that the half-Heusler phases were obtained. The microstructures of the melt spun thin ribbons were studied by the scanning electron microscope and transmission electron microscope. The thin ribbons were in the size of a few hundreds nanometers which didn't grow too much during the sintering process. Nanocrystals were found in the crystal grains. The carrier concentration increased for the melt-spinning samples compared with the levitation melting samples, indicating that the nanocrystals were metallic. The increasing boundary scattering after melt-spinning