The problems of increasing the thermoelectric figure of merit of polycrystalline misfit layered compounds on (Gd-=SUB=-x-=/SUB=-Dy-=SUB=-1-x-=/SUB=-S)-=SUB=-z-=/SUB=-NbS-=SUB=-2-=/SUB=- example

Abstract

The lattice disorder of different architecture and dimensions influence on the thermoelectric properties (Seebeck coefficient S, resistivity rho, total thermal conductivity kappatot,, power factor S2/rho, figure of merit ZT) of the polycrystalline ternary sulfides MTS3 was studied. The high-temperature misfit layered compounds (MS)zNbS2 (MS is GdxDy1-xS solid solutions) were chosen as objects of the study. The variation of gadolinium concentration along the series x=0.0, 0.1, 0.2, 0.5, 1.0 allowed one to alter the short-range and the long-range order of the crystal lattice and to study their effect on thermoelectric parameters of (GdxDy1-xS)zNbS2. At low concentration of x=0.1 the crystallite size increases, cause the deformation stresses decrease and, thereby, leads to an abnormal changes of S, rho, kappatot values and ZT decrease. An increase of the gadolinium concentration (x=0.2-0.5) alters the electronic structure and the interatomic bonding character of the incommensurate subsystems [GdxDy1-xS] and [NbS2]. In this case, S and rho values remains practically unaffected, while the thermal conductivity value decreases by 40% and ZT increases by 2 times. The nature of this phenomenon and the anisotropy of the thermoelectric properties were discussed. Keywords:: misfit layers compounds, thermoelectric properties, lattice disorder, solid solution, crystallite boundaries.