A possibility of Pd based high entropy alloy for hydrogen gas sensing applications

Abstract

Diffusion of H atoms in Pd-based alloy usually takes place through octahedral voids for face centered cubic (FCC) metals and alloys. Transition metals are preferred as the alloying element for Pd-based alloy because electron removal and addition from Pd, and the number of vacant d-states of Pd can be regulated by lacking the deformation of electronic structure of Pd. In addition, the alloying alters a lattice constant and hydrogen permeability, thereby improving the mechanical, chemical stabilities of Pd-based devices and reduce the expensive cost of Pd raw material. High entropy alloys (HEA) have been investigated as an important contributor in field of microelectronics as a catalyst, diffusion barrier, and anode materials for a solid oxide fuel cell (SOFC). HEA's of Pd, Ag, Ni, Cu, Au, Rh, Pt and Ir are designed empirically and their lattice constants, corresponding an octahedral void size are analyzed with pure Pd, thus suggesting them as a potential candidate for hydrogen storage applications in the future. The core reason for designing HEA is to overcome the problem of cost and availability of Pd and Pd-rich binary alloys. In this paper, we calculated the lattice parameters using the Vergards law, octahedral void size, lattice distortion and cost for PdAg-based HEA's of 20 combinations.