Thermal expansion of rhodium, iridium, and palladium at low temperatures

Abstract

Coefficients (α) of linear thermal expansion of Rh, Ir, and Pd are reported to be respectively 8.45, 6.65, and 11.78×10⁻⁶° K⁻¹ at 238°K, and 3.50, 3.43, and 6.21×10⁻⁶°K⁻¹ at 75°K. At temperatures below 10°K, α may be represented by

$$\begin{gathered} 10^{10} \alpha = 20{\rm T} + 0.052{\rm T}^3 (Rh) \hfill \\ 10^{10} \alpha = 9{\rm T} + 0.070{\rm T}^3 (Ir) \hfill \\ 10^{10} \alpha = 40.5{\rm T} + 0.435{\rm T}^3 (Pd) \hfill \\ \end{gathered} $$

TheT andT ³terms are identifiable with electron and lattice vibrational components, respectively. Corresponding Grüneisen parameters are γ (electron)≈2.8, 2.7, and 2.22 for Rh, Ir, and Pd, and γ ₀ (lattice)≈2.0, 2.3, and 2.25.