Systematic study of ferromagnetic phase stability of Co-based Heusler materials with high figure of merit: Hunt for spintronics and thermoelectric applicability

The high throughput thermoelectric devices are considered a promising futuristic energy source to control global warming and realize the dream of green energy and a sustainable environment. In the present work, strict and highly accurate spin-polarized density functional theory combined with the Boltzmann transport scheme has been applied to extract the properties of Co2XAl (X = Zr, Nb, Hf) Heuslers. The mechanical stability appropriately prefers their cubic crystalline geometry with the ductile character of these alloys. The modified Becke-Johnson potential illustrates better results than GGA and GGA+U functionals. The band profile is found to be n-type (indirect bandgap) for Co2NbAl and p-type (direct bandgap) for Co2ZrAl and Co2HfAl Heuslers near the Fermi level. The preferably asymmetric density of states and structural optimization demonstrate the ferromagnetic character of these Heuslers. The formation and cohesive energy recommend that these alloys are thermodynamically stable. The Co2XAl (X = Zr, Nb, Hf) Heuslers deliver the significant value of the vital parameters like the Seebeck coefficient, zT, and power factor, which recommends the better thermoelectric response for practical applications. The improved stability, ductile behavior, durability, and rational zT should turn helpful in deciding the scalable potential of Co2XAl (X = Zr, Nb, Hf) materials for the design of long-lasting thermoelectric generators and flexible electronic devices.