A high throughput search of efficient thermoelectric half-Heusler compounds

Stable half Heusler compounds formed from elements of three specific groups in the periodic table viz.
X_pX'_1−p Y_q Y' _1−q Z_rZ'_1−r (with X, X' = Ti, Zr, Hf, Y, Y' = Ni, Pd, Pt and Z, Z' = Ge, Sn, Pb and p, q, r = 0, 0.25, 0.75 and 1) via various stoichiometric isoelectronic elemental substitution at the X, Y and Z sites respectively are investigated. Intelligent filters are employed at each step of our high throughput density functional theory calculations to filter compounds with improved figure of merit. While confirming several known results, calculations also reveal unknown pathways to improve the thermoelectric performance of the compound class. 50% X as well as Z site substitution of the parent Heusler individually are found to marginally enhance the power factor for both p- and n-type doping, while leading to considerable enhancement in figure of merit (by ∼24 %) specifically due to lowering of lattice thermal conductivity. The present study confirms the experimental scenario that Y site substitution does not lead to enhancement of the powerfactor because of the breaking of band degeneracies at the high symmetry points.