Thermoelectric nanocrystalline YbCoSb laser prepared layers
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Filled thermoelectric Yb x Co4Sb12 layers were prepared by pulsed laser deposition method. The Yb0.19Co4Sb12 target was fabricated by hot pressing. Various deposition conditions were tested: target—substrate distance d T–S (4 or 6 cm), ambient argon pressure (from 0.5 to 13 Pa), laser repetition rate (from 3 to 10 Hz), substrate temperature (from 250 to 400 °C) and laser fluence (in region from 0.8 to 5 J cm−2). Film roughness was determined by mechanical profilometer and by AFM. For d T–S = 4 cm we observed a deficit of Yb and surplus of Co. Sb was transferred from target to film roughly stoichiometrically (as measured by EDX). Films created at 0.8 J cm−2 exhibited generally poor stoichiometry and mechanical properties. Optimal conditions and stoichiometric transport were found for d T–S = 6 cm and 13 Pa of Ar. XRD shows that the films were nanocrystalline with CoSb3 structure. Grain size was in the range of ~50–80 nm. Temperature dependence of Seebeck coefficient and power factor was measured. Thermoelectric efficiency ZT ~ 0.04–0.05 was measured at room temperature using Harman method. In dependence on layers quality, we calculated thermal conductivity λ ~ 0.4–1.3 W K−1 m−1.
KeywordsAtomic Force Microscope Power Factor Pulse Laser Deposition Seebeck Coefficient Laser Repetition Rate
The project has been supported by Czech Grant Agency under GA13-33056S and the Grant Agency of the Czech Technical University in Prague under Grant No. SGS14/168/OHK4/2T/17. We thank Dr. Ludvik Beneš for XRD measurement.
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