Re: barium titanate doorknob caps/beryllium

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Luc, Al, All!

>P.S. I remember people tried to use titanium oxide ( DC of 45 )
>and titanium dioxide ( DC of 110 ) in different binder without
>great success.


I replied off-list to Al's original question because there was a *lot*
of off topic stuff in my reply.  Regarding the use of high K
dielectrics in a binder, it's very unlikely to be useful.  The problem
is the tiny spaces of low K material between the high K particles.
Think of the magnetic analogy of an air gap in the magnetic circuit of
a choke core, where the low permittivity air gap causes a major change
in the overall characteristics of the choke.

Even if the low K binder occupies a mere 5% of the total volume (and
that's not a lot of binder when you start thinking about how particles
pack together and what spaces are left between them) if you do the
maths you find you're limited to a net value of K for the composite of
less than 37 with a material of K=100.  I found this out the hard way.
Using compacted titanium dioxide powder, the effective K I measured
was only around ten, which implies more than 15% air spaces in my
particular sample.  To be efficient, a high K dielectric does need to
be a solid, contiguous, sintered mass.  For instance, if you could get
a material with infinite K, just 10% of binder (or air or whatever)
would reduce the effective K to only 28!

Dunckx
Geek#1113 (G-1)