Effects of Rh on the thermoelectric performance of the p-type Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} half-Heusler alloys

• Published in: Journal of solid state chemistry Vol. 183; no. 5
• Main Authors: Maji, Pramathesh, Department of Chemistry, University of New Orleans, New Orleans, LA 70148, Takas, Nathan J., Misra, Dinesh K., Gabrisch, Heike, Stokes, Kevin, Department of Physics, University of New Orleans, New Orleans, LA 70148, Poudeu, Pierre F.P.
• Format: Journal Article
• Language: English
• Published: United States 15.05.2010
• Subjects: ALLOYS; ALUMINIUM ALLOYS; ANTIMONY ALLOYS; COBALT ALLOYS; COPPER ALLOYS; COPPER BASE ALLOYS; CORROSION RESISTANT ALLOYS; ELECTRICAL PROPERTIES; GRAIN BOUNDARIES; GRAIN SIZE; HAFNIUM ALLOYS; HEUSLER ALLOYS; MANGANESE ALLOYS; MATERIALS; MATERIALS SCIENCE; MICROSTRUCTURE; PHYSICAL PROPERTIES; PLATINUM METAL ALLOYS; RHODIUM ALLOYS; SCATTERING; SIZE; TEMPERATURE RANGE; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 1000-4000 K; THERMAL CONDUCTIVITY; THERMODYNAMIC PROPERTIES; THERMOELECTRIC MATERIALS; THERMOELECTRIC PROPERTIES; TIN ALLOYS; TRANSITION ELEMENT ALLOYS; ZIRCONIUM ALLOYS
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2010.03.023

We show that Rh substitution at the Co site in Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} (0<=x<=1) half-Heusler alloys strongly reduces the thermal conductivity with a simultaneous, significant improvement of the power factor of the materials. Thermoelectric properties of hot-pressed pellets of several compositions with various Rh concentrations were investigated in the temperature range from 300 to 775 K. The Rh 'free' composition shows n-type conduction, while Rh substitution at the Co site drives the system to p-type semiconducting behavior. The lattice thermal conductivity of Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} alloys rapidly decreased with increasing Rh concentration and lattice thermal conductivity as low as 3.7 W/m*K was obtained at 300 K for Zr{sub 0.5}Hf{sub 0.5}RhSb{sub 0.99}Sn{sub 0.01}. The drastic reduction of the lattice thermal conductivity is attributed to mass fluctuation induced by the Rh substitution at the Co site, as well as enhanced phonon scattering at grain boundaries due to the small grain size of the synthesized materials. - Graphical abstract: Significant reduction of the lattice thermal conductivity with increasing Rh concentration in the p-type Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} half-Heusler materials prepared by solid state reaction at 1173 K.