What is Thermal Conductivity?
- In metals, valence electrons conduct heat energy + electric current
- Phonons – lattice vibrations – transport heat through non-metals
- κ= ραCp
- ρ = density
- α = thermal diffusivity
- Cp = heat capacity
- Transport is intrinsically important for thermal conductivity
- Phonon scattering → insulation
Thermal Conductivity, Electrical Insulation
Graphite:
- Full delocalization of π electrons → full aromaticity
- Electrical delocalization in graphite leads to high electrical conductivity and high thermal conductivity
hexagonal-Boron Nitride:
- Electrons are mainly distributed on N atoms → partial aromaticity
- Thermal conductivity arises from phonon vibrations
Lattice Vibration Modes of h-BN
9 optical modes which decompose at the Brillouin zone center as E1u + A2u + 2 E2g + 2 B1g
In plane and out-of-plane vibrational modes in TC THz frequency range (B1g, E2g)
Nanophotonics 2020, 9 (11), 3483 – 3504
In-Plane vs Through-Plane Thermal Conductivity
Percolation