Effects of Heavy Element Substitution on Electronic Structure and Lattice Thermal Conductivity of Fe_(2)VAl Thermoelectric Material

摘要

By using first-principles cluster calculations, we identified that Ta or W substitution for V is useful for decreasing the lattice thermal conductivity of the Fe_(2)VAl Heusler alloy without greatly affecting the electron transport properties. It was clearly confirmed that the Fe_(2)(V_(1-x)Ta_(x))Al_(0.95)Si_(0.05) (x velence 0, 0.025, 0.05), Fe_(2)(V_(0.9-x)Ta_(x)Ti_(0.1))Al (x velence 0, 0.10, 0.20), and Fe_(2)(V_(0.9-2x)W_(x)Ti_(0.1+x))Al (x velence 0, 0.05, 0.10) alloys indeed possessed large Seebeck coefficient regardless of the amounts of substituted elements, while their lattice thermal conductivity was effectively reduced. As a result of partial substitution of Ta for V, we succeeded in increasing the magnitude of the dimensionless figure of merit of the Heusler phase up to 0.2, which is five times as large as the Ta-free compound.