Ball milling effects for induced carriers and reduced grain size on thermoelectric properties in Bi_{1− x}Sr_xCuSeO

Abstract

We have investigated the ball milling effects for thermoelectric Bi1− x Sr x CuSeO materials. The characteristic rotation speed R for the ball milling exists, at which the crystallite size of the starting powder suddenly decreased. The grain size in the bulks sintered using ball-milled powders also decreased and thermoelectric properties were enhanced mainly by the induced carriers, rather than by the reduction in thermal conductivity. The ball milling effects of carrier doping on thermoelectricity are discussed.

BiCuSeO Thermoelectrics: An Update on Recent Progress and Perspective

“…Extensive experiments confirmed that alkaline-earth metals doping is effective to enhance the thermoelectric performance of Bi 1− x M x CuSeO (M = Mg, Ca, Sr, Ba) [1,2,4,6,30,63,64], among them the high-performance doped BiCuSeO systems exhibit the extremely low thermal conductivity. However, trying to explain origins of low thermal conductivity via investigating on the microstructures of these alkaline-earth-metal doped BiCuSeO remain largely unexplored.…”

Crystal orientation, crystallinity, and thermoelectric properties of Bi0.9Sr0.1CuSeO epitaxial films grown by pulsed laser deposition

“…22,23) ρ(300 K) of the present Sr-doped film, in which a small amount of Bi deficiency existed and hole carriers were created, was smaller. 20) S(300 K) of the present Sr-doped film is the smallest, among those of other materials. The main difference observed in the films is the growth temperature T s , which is 573 K for the present film and is lower than 773 K for the Ca-doped film (x = 0.1) 22) and 673 K for the Pb-doped film (x = 0.06).…”

“…The results of the element analysis for the films grown on STO are nearly the same as those for the films on MgO, regardless of the lattice mismatch between the film and the substrate. 20) are also shown. The ρ(T ) and S(T ) values of the films at 300 K are smaller than those of the SPS bulk, which change independent of P Ar , and suggest that the hole carriers are introduced into the films during PLD.…”

“…Figures 8(a) and 8(b) respectively show the temperature dependences of the electrical resistivity ρ(T ) and Seebeck coefficient S(T ) of the Bi 0.9 Sr 0.1 CuSeO films grown on MgO at T s = 573 K at various P Ar values. For comparison, the values of the target bulk fabricated by SPS, which were independent of the direction of the applied pressure during SPS, 20) are also shown. The ρ(T ) and S(T ) values of the films at 300 K are smaller than those of the SPS bulk, which change independent of P Ar , and suggest that the hole carriers are introduced into the films during PLD.…”

“…19) We have investigated the ball milling effects for Bi 1−x Sr x CuSeO (x ¼ 0; 0:1) bulk materials fabricated by a spark plasma sintering (SPS) method, in which thermoelectric properties were enhanced by the use of ball-milled powder, mainly owing to the induced carriers, rather than the reduction in thermal conductivity. 20) A thin film of a thermoelectric material is preferably used to realize a fully c-axis texture and to tremendously enhance ZT via the quantum confinement effect and interface engineering. However, there are few reports on thin films of the BiCuSeO system.…”