Experimental determination of phonon thermal conductivity and Lorenz ratio of single crystal metals: Al, Cu and Zn

TL;DR

This study experimentally measures the lattice thermal conductivity and Lorenz number of single crystal Al, Cu, and Zn across 5 to 60 K using a magnetothermal resistance method, revealing temperature-dependent behaviors.

Contribution

It introduces a magnetothermal resistance technique to accurately determine phonon thermal conductivity and Lorenz ratio in single crystal metals over a broad temperature range.

Findings

Phonon thermal conductivity peaks around one tenth of the Debye temperature.

Lorenz number deviates from the Sommerfeld value at intermediate temperatures.

Method effectively isolates lattice thermal conductivity in metals.

Abstract

We use a magnetothermal resistance method to measure lattice thermal conductivity of pure single crystal metals over a wide range of temperatures. Large transverse magnetic fields are applied to suppress electronic thermal conduction. The total thermal conductivity and the electrical conductivity are measured as functions of applied magnetic field. The lattice thermal conductivity is then extracted by extrapolating the thermal conductivity versus electrical conductivity curve at zero electrical conductivity. We used this method to experimentally measure the lattice thermal conductivity and Lorenz number in single crystal Al (100), Cu (100) and Zn (001) in a temperature range of 5 to 60 K. Our results show that the measured phonon thermal conductivity versus temperature plot has a peak around one tenth of the Debye Temperature, and the Lorenz number is found to deviate from the Sommerfeld value in the intermediate temperature range.