Se substitution and micro-nano-scale porosity enhancing thermoelectric Cu_2Te

Binary Cu-based chalcogenide thermoelectric materials have attracted a great deal of attention due to their outstanding physical properties and fascinating phase sequence.However,the relatively low figure of merit z T restricts their practical applications in power generation.A general approach to enhancing z T value is to produce nanostructured grains,while one disadvantage of such a method is the expansion of grain size in heating-up process.Here,we report a prominent improvement of z T in Cu_2Te_(0.2)Se_(0.8),which is several times larger than that of the matrix.This significant enhancement in thermoelectric performance is attributed to the formation of abundant porosity via cold press.These pores with nano-to micrometer size can manipulate phonon transport simultaneously,resulting in an apparent suppression of thermal conductivity.Moreover,the Se substitution triggers a rapid promotion of power factor,which compensates for the reduction of electrical properties due to carriers scattering by pores.Our strategy of porosity engineering by phonon scattering can also be highly applicable in enhancing the performances of other thermoelectric systems.