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 made the lattice thermal conductivity decrease.