Thermal Conductivity of Common Metals
Thermal conductivity (κ, in W/m·K) measures how effectively a material conducts heat. In metals, heat conduction is dominated by free electron transport, governed by the Wiedemann–Franz law, which relates electrical conductivity and thermal conductivity via the Lorenz number. This makes metals excellent thermal conductors, though the degree varies significantly based on electron mobility, crystal structure, and impurity content.
The table below summarizes the thermal conductivity of several common metals at room temperature (approximately 300 K), based on standard bulk, annealed samples. All values are approximate and can vary depending on alloying, grain size, and temperature.
| Metal | Thermal Conductivity (W/m·K) | Notes |
|---|---|---|
| Silver | 429 | Highest among pure metals |
| Copper | 401 | Widely used due to high κ and low cost |
| Gold | 318 | High κ, but expensive |
| Aluminum | 237 | Lightweight, good thermal conductor |
| Brass | 109 | Alloy; lower κ due to scattering |
| Iron | 80 | Ferromagnetic effects influence κ |
| Steel (plain) | ~50 | Alloy-dependent, generally low |
| Titanium | 22 | Low κ despite metallic bonding |
| Lead | 35 | Low κ due to heavy atoms, soft lattice |
| Stainless Steel | 16 | High alloying reduces electron mobility |
| Mercury | 8.3 | Liquid at room temp; poor metal κ |
Discussion
Silver is the most thermally conductive metal due to its high electron mobility and minimal scattering. Copper is nearly as conductive but much cheaper, making it a standard in thermal and electrical applications. Alloys like brass and steel show significantly reduced conductivity due to increased electron scattering from disorder and impurity atoms.
Thermal conductivity is not solely dictated by atomic mass or density; rather, it's a complex interplay between electronic structure and phonon scattering. Metals with high thermal conductivity are often also excellent electrical conductors, but exceptions arise when lattice vibrations dominate, especially in alloys or at high temperatures.