Size-dependent thermopower in nanocrystalline nickel

Soni, Ajay; Okram, Gunadhor S.
July 2009
Applied Physics Letters;7/6/2009, Vol. 95 Issue 1, p013101
Academic Journal
Thermopower (Sn) of compacted nanocrystalline Ni of average particle size D=38, 32, and 25 nm at low temperatures (5–300 K) is reported here. Sn exhibits striking deviations from bulk thermopower Sbulk behavior revealing evolution of Sn with change in D. As D decreases, there is significant decrease in Sn, gradual disappearance of phonon drag minimum and sign change to positive below 38 K compared to usual negative Sbulk. They have been attributed to electron and phonon scattering at grain boundaries and phonon confinement. Small minima observed near 25 K in thermopower difference ΔS are correlated with superparamagnetic transitions.


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