Why is diamond an electrical insulator while it is a good conductor of heat?

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2008-08-26 09:41:06

Diamond is a good thermal conductor. But it is an excellent

electrical insulator. How?

Diamond crystal is a three-dimensional network of carbon atoms.

All carbon atoms in the network are strongly bonded by

carbon-carbon covalent bonds.

The diamond crystal has a highly symmetric cubic structure. The

carbon atoms in diamond are precisely aligned. Thus diamond is an

ideal crystal. Atoms in the crystal lattices in solids vibrate.

These vibrations, called the atomic vibrations facilitate

thermal conduction (transport of heat) in solids. In an ideal

crystal, the lattices are so precisely aligned that they do not

interact with each other.

Therefore an ideal crystal conducts better than a non-ideal

crystal resulting in ideal crystals having good thermal

conductivity, which is a measure of heat conduction. Diamond being

an ideal crystal is thus a good thermal conductor.

Mobile electrons facilitate electrical conduction - flow of

current in solids. There are no free mobile electrons in diamond

crystal to facilitate electrial conduction. Thus diamond is an

excellent electrical insulator. In more simple terms, Diamond has a

unique atomic structure. Each of the Carbon atom's valence

electrons is taken up in covalent bonding, so each electron is

localised. This means that no one electron is free to pass

an electric current through the Diamond - thus, Diamond cannot

carry an electrical current; there is nothing to pass the current


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