Re: resistivity versus temperature

["John S. Denker" <jsd@MONMOUTH.COM>]

On 04/14/2003 05:44 PM, Wolfgang Rueckner wrote:
> I have a couple of introductory physics texts which show graphs of
> the resistivity of various common metals as a function of temperature
> (from cryogenic temps to very high).  They're very nice looking
> graphs but, unhappily, the graphs don't agree with each other at all,
> nor do they agree with specific numbers I've found in the Handbook of
> Physics & Chemistry.  And of course the texts don't reference the
> sources from which the graphs have been produced.  Do any of you know
> of a good reference for such data and/or graphs?  Thanks in advance

The low-temperature resistivity of something like
"copper" can be almost anything you can imagine,
because it is more sensitive to the impurity
content than to any intrinsic property of the
metal.  Indeed, commonly people express the purity
in terms of the "RRR" (residual resistivity ratio),
i.e. the ratio of the low-temperature restivity to
the room-temperature resistivity.

Magnetic impurities (e.g. oxygen) scatter things
more effectively than non-magnetic impurities do.

At non-low-temperatures (including room temperature
and above), all "copper" is the same, because the
resistivity is dominated by scattering by thermal
phonons.

An alloy such as brass is essentially the world's
most impure metal, so its resistivity is high,
independent of temperature at reasonable temperatures,
and sensitive to details of composition, history,
et cetera.

This is covered in detail in solid-state physics
books e.g. Ashcroft & Mermin.