Temperature dependence of electrical resistivity for nanocrystalline Mg3+xSb2 prepared by mechanical alloying

Abstract

The temperature dependence of dc electrical resistivity of nanocrystalline Mg3+xSb2 (nano-Mg3+xSb2) (mean grain sizes d ∼ 30 nm), prepared by mechanical alloying plus hot-pressing (HP), was investigated below room temperature. The results indicate that composition deviation x from stoichiometry has a strong influence on the temperature dependence of the resistivity. For the specimens with smaller absolute composition deviation |x|, their resistivity ρ increased exponentially with decreasing temperature, i.e. lnρ ∝ 1/T in the whole temperature range investigated. However, for the specimens with very large |x| or those with a large |x| after HP for a longer time, the relationship ln ρ ∝ 1/T existed only in the high temperature regime; at low temperatures Mott's ln ρ ∝ T−1/4 law was observed in these specimens, indicating that large compositional deviations produced strong random potential, which led to the formation of considerable localized states. By fitting the experimental data to Mott's T−1/4 law, we estimated the density of localized states N(EF) at the Fermi level, which was found to increase with increasing composition deviation |x| in nano-Mg3+xSb2.