Effects of Metal Particles Decoration on n-Type Chalcogenides Processed by Open Die Pressing

The effects of copper particles dispersed into Bi1.9Sb0.1Te2.85Se0.15 nanopowders and sintered by open die pressing (ODP) have been investigated. Submicrometric copper particles were obtained by decomposing copper acetate molecules dispersed into chalcogenides nanopowders. The acetate powders were decomposed during the sintering process at 390 A degrees C obtaining a fine dispersion of copper particles with dimensions in the order of 500 nm. Contents up to 0.2 wt.% of copper were investigated. ODP, previously introduced as a forming process for sintering and texturing p-type (Bi0.2Sb0.8)(2)Te-3 nanopowders, has been applied to n-type chalcogenide: the mixed alloy nanopowders and copper acetate were compacted inside a metallic protective shell and fast pressed between two heated plates, keeping the composite under load for sintering. ODP processing ensures complete consolidation of nanopowders and material texturing with the basal (00l) planes of the hexagonal crystal cell oriented parallel to the plates. The X-ray diffraction pattern shows an orientation factor, f, obtained by the Lotgering method, up to 64 %. Thermoelectric performance of the samples was measured by the Harman method in the range of 20-170 A degrees C. Figure of merit (ZT) behavior with temperature was improved in copper-dispersed samples showing a shift of the maximum value at higher temperatures. This effect can be mainly associated with an improvement of electrical conductivity, due to the presence of the copper particles.