Re: barium titanate doorknob caps/beryllium

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

Hi Georg, All!

>perhaps it is a silly question but why you only want the barium
titinate as
>a ceramic? If I recall correctly you must use the average dielektrik
>constant (you have to pay attention to thickness) if you use
different
>dieelctrics between two electrodes. IMO you can submerge the BaTi-
>powder in something which is also a good insulator, perhaps
>paraffin. <snip>

Ah, if only it were this simple!  Unfortunately when using a composite
made by mixing particles with a binder it isn't so easy.  I've already
made some comments in my reply to Luc's posting, so I'll just give you
the formula:

Keff = [(a^2 K) + 1 - a^2] / [K - aK + a]

where Keff is the effective dielectric constant of the composite, K is
the dielectric constant of the pure bulk material and a^3 is the
proportion (100% = 1,0) of the composite total volume occupied by
material of dielectric constant K (assuming that the K of the "binder"
is negligible in comparison).  Example: if the binder occupies 10% of
the total volume, a^3 = 0,9 and therefore a = cube root (0,9) =
0,965... from which a^2 = 0,932...  If then K = 100, Keff = 21,7 :-(

I only wish it was otherwise!

Dunckx
Geek#1113 (G-1)