Features of mechanisms of electrical conductivity of semiconductor solid solution Zr1-xAlxNiSn

Abstract

The structural, electrokinetic, energetic, and magnetic properties of the semiconductor solid solution Zr_1-xAl_xNiSn, obtained by doping the half-Heusler phase n-ZrNiSn with Al atoms by substituting Zr atoms in the 4a position, were investigated. It was established that Al atoms can occupy different crystallographic positions, causing complex transformations of the crystal and electronic structures. It was shown that in Zr_1-xAl_xNiSn, х = 0–0.02, the increase in the unit cell parameter a(x) is due to the preferential substitution of the Ni atoms present (r_Ni = 0.125 nm) in the 4a position by Al atoms (r_Al = 0.143 nm) generating defects and energy states of an acceptor nature. The decrease in the parameter a(x) for Zr_1-xAl_xNiSn, 0.02 < x ≤ 0.04, is caused by the replacement of larger Zr atoms (r_Zr = 0.160 nm, 4d²5s²) with smaller Al atoms, which also generates defects and energy states of an acceptor nature. At concentrations of Zr_1-xAl_xNiSn, x > 0.04, Al atoms are mainly localized in tetrahedral voids of the structure, generating defects and energy states of a donor nature. The ratio of the concentrations of the generated energy states of Zr_1-xAl_xNiSn determines the position of the Fermi level ε_F. The performed studies allowed us to identify the mechanisms of electrical conductivity to determine the conditions for the synthesis of thermoelectric materials Zr_1-xAl_xNiSn with the maximum efficiency of converting thermal energy into electrical energy.