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Phase formation, stability, and oxidation in (Ti, Zr, Hf)NiSn half‐Heusler compounds (Phys. Status Solidi A 6∕2014)
Author(s) -
Gałązka Krzysztof,
Populoh Sascha,
Sagarna Leyre,
Karvonen Lassi,
Xie Wenjie,
Beni Alessandra,
Schmutz Patrik,
Hulliger Jürg,
Weidenkaff Anke
Publication year - 2014
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201470235
Subject(s) - materials science , intergranular corrosion , thermoelectric effect , grain boundary , phase (matter) , metallurgy , kelvin probe force microscope , structural stability , analytical chemistry (journal) , microstructure , thermodynamics , nanotechnology , chemistry , atomic force microscopy , physics , organic chemistry , structural engineering , chromatography , engineering
Thermoelectricity offers the unique possibility of a direct conversion of heat to electricity. Half‐Heusler compounds based on TiNiSn are of great interest for thermoelectric research due to their promising electrical properties. However, for an efficient energy conversion their thermal conductivity has to be lowered. One strategy is to reduce the phonon mean free path by isoelectric substitution of Ti by Zr and Hf, as in the (Ti 0.33 Zr 0.33 Hf 0.33 )NiSn in this work (see pp. 1259–1266 ). The complex phase composition of these compounds is revealed in the SEM image, where brighter (Zr,Hf)‐rich half‐Heusler grains are separated by Ti‐rich intergranular phases. Gałązka et al. analyze the stability of the compound by in‐situ Atomic Force Microscopy and Scanning Kelvin Probe Microscopy, which allow real‐time tracking of topographic and chemical changes of the sample surface at temperatures up to 423 K. The sequence of experimental images reveals topography and Volta Potential Difference changes resulting from irreversible phase segregation on the grain boundaries within the Ti‐rich intergranular phase.