Thermoelectric nanocrystalline YbCoSb laser prepared layers

Abstract

Filled thermoelectric YbxCo4Sb12 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 dT–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 dT–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 dT–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.