Mechanochemical production and investigation of nanocomposite thermoelectric ceramics based on heavy multicomponent doped /spl beta/-FeSi/sub 2/

Abstract

Iron disilicide is a prospective thermoelectric material for generators, available for mass production. It has low efficiency (ZT/spl sim/0.2-0.4). There are ways to increase the efficiency: particle size decrease (to nanoscale), unconventional alloying elements and multicomponent doping, heterophase additives, 2D (3D) superlattice production. The aim of this work is to synthesise mechanochemically the nanocomposite based on doped /spl beta/-FeSi/sub 2/ and to investigate the influence of multicomponent doping on the thermoelectric properties. The mechanical alloying of elements was carried out in an intensive planetary ball mill with ball acceleration of 600 m/sec/sup 2/. The intensity factor was varied by different ball diameters (3-15 mm). The powder samples were analyzed by the X-ray diffractometry. After mechanical alloying, the phase content was mixtures of FeSi, /spl beta/-FeSi/sub 2/ and Fe(Si). The average particle sizes were 200-1000 nm. The reaction sintering leads to nanocomposites with 20-100 nm grains. After compacting and low temperature annealing, the phase content was the thermoelectric beta-iron disilicide. The dopants status and electrical characteristics were investigated.