Bill's comments are in general excellent. But I take issue with one.
Aluminum is an electron conductor, not a hole conductor. It is used to dope
Si - to make it p-type.
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In ceramics, there is often more than one charge carrier that contributes to
the electrical conduction. Here, a term called the transference number is
used to define the fraction of the total conductivity that each type of
charge carrier contributes.
As stated in an excellent text, Introduction to Ceramics, by Kingery Bowen
and Uhlmann, "the problem of interpreting and controlling electrical
conductivity in ceramics consists of characterizing the concentration and
mobility of each possible current carrier and then summing these
contributions to obtain the total conductivity (p. 852)."
For those who want to wade more deeply into this, Kroger-Vink notation and
diagrams are used to represent the concentration of the many types of
charged defects that exist in ceramics, often as a function of oxygen
partial pressure.
Larry Woolf; General Atomics; 3550 General Atomics Court, San Diego, CA
92121; Phone:858-455-4475; FAX:858-455-4268; http://www.sci-ed-ga.org
-----Original Message-----
From: William Beaty
Subject: Re: "Electric current" does not mean "electron flow"
Here's a dirty little secret: Some common metals are hole conductors as
well as electron conductors. If I recall, aluminum is one example. FOr
those who insist that elctric current is REALLY a flow of electrons, well
they'd better stick to copper wires and never use aluminum.
One final note: positive conductors do exist. During an electric current
in frozen water, the normal ions are locked into the crystal, and only the
+H ions can flow... and a +H ion is a bare proton. Ice is a "proton
conductor". Some types of exotic plastic conductors and ceramic
conductors are also Proton Conductors.