Investigation of Chromium (III) Sulfide’s Thermal Resistance using Scanning Thermal Microscopy

Thermoelectric materials can directly convert this waste heat into electricity; therefore, they have attracted attention as environmentally friendly solutions to an ever-growing energy demand. The conversion efficiency of thermoelectric material is based on the dimensionless figure of merit zT, defined by zT=S²σT/κ, where S, σ, and κ are defined as the Seebeck coefficient, electrical conductivity, and thermal conductivity, respectively. One way to increase a materials zT value is to reduce its thermal conductivity. The nano structuring of a thermoelectric material increases phonon scattering at the grain boundaries and therefore lowers thermal conductance. In this study, we use an extension of atomic force microscopy (AFM) – scanning thermal microscopy (SThM) – to measure the thermal resistance, related to the thermal conductivity, of chromium (III) sulfide (Cr₂S₃) nanoparticles. The data shows an inverse linear relationship between the recorded probe resistance values as a function of particle height at a constant radius and a logarithmic relationship between probe resistance values and the radius of a particle at a constant height. These relationships were explained through the Fourier law of heat conduction.