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Author Mallick, Md. Mofasser ♦ Vitta, Satish
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY ♦ ANNEALING ♦ ELECTRIC CONDUCTIVITY ♦ GERMANIUM COMPOUNDS ♦ HAFNIUM COMPOUNDS ♦ HEAT ♦ HEUSLER ALLOYS ♦ IMPURITIES ♦ MELTING ♦ NICKEL COMPOUNDS ♦ ORTHORHOMBIC LATTICES ♦ REDUCTION ♦ SPECIFIC HEAT ♦ TEMPERATURE RANGE 0273-0400 K ♦ TEMPERATURE RANGE 0400-1000 K ♦ TERNARY ALLOY SYSTEMS ♦ THERMAL CONDUCTIVITY ♦ THERMAL DIFFUSIVITY ♦ THERMOELECTRIC PROPERTIES ♦ X-RAY DIFFRACTION
Abstract The half-Heusler alloy HfNiGe has been synthesized by arc melting from high purity elements followed by annealing at 1000 K for 6 days to homogenize completely. The X-ray diffraction pattern indicates the presence of mainly an orthorhombic phase with small amount of other binary phases. The electrical resistivity is found to be low and increases slightly with temperature from 14 µΩ-m to 24 µΩ-m, indicating a semi metallic behavior. As a result the Seebeck coefficient is found to be low and also increases with temperature from −11 µV K{sup −1} to −19.5 µV K{sup −1}. The thermal conductivity has been determined using a combination of heat capacity and thermal diffusivity. It decreases from ~ 1.9 Wm{sup −1}K{sup −1} at room temperature to ~ 0.007 Wm{sup −1}K{sup −1} at 843 K, an extremely low value for a half-Heusler alloy. The thermal conductivity reduction is found to be mainly due to a sharp decrease in heat capacity for T> 650 K. This leads to a divergence of figure of merit at high temperatures, >800 K, from ~0.05 to 2 at 843 K.
ISSN 0094243X
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-05-23
Publisher Place United States
Volume Number 1731
Issue Number 1


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