Room temperature mechanical properties of polycrystalline YbAl3, a promising low temperature thermoelectric material

Intermetallic YbAl3 in the L12 (AuCu3) phase is a promising material for low temperature thermoelectric applications. However, there is no experimental data in the literature on the mechanical properties of YbAl3, although the design and development of thermoelectric modules incorporating YbAl3 will require mechanical property data. Using resonant ultrasound spectroscopy (RUS), the room temperature Youngʹs modulus, shear modulus, bulk modulus and Poissonʹs ratio were determined as a function of volume fraction porosity, P, for specimens densified by both hot pressing (HP) and pulsed electric current sintering (PECS) polycrystalline specimens, where P ranged from 0.030 to 0.233 and mean grain sizes ranged from 0.5 to 1.4 μm. In addition, the longitudinal and acoustic wave speeds and the Debye temperature were measured. Using Vickers indentation, the hardness and fracture toughness of the specimens were also measured. Despite microstructural differences between the HP and PECS-processed specimens, the porosity dependence of the mechanical properties was a function of the total volume fraction porosity, P, independent of the details of the size and spatial distribution of pores within individual specimens.