Re: Dialectric Constant

Tesla List wrote:
> >From rwall-at-ix-dot-netcom-dot-comMon Aug  5 20:26:29 1996
> Date: Sun, 4 Aug 1996 22:04:35 -0700
> From: Richard Wayne Wall <rwall-at-ix-dot-netcom-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Dialectric Constant
> 8/4/96
> At a hamfest yesterday, I bought a Barker and Williamson CX 62 C
> variable air condenser.  It's 8"x6"x6" and made with ceramic and
> polished stainless steel plates that are 1/2" apart.  The craftmanship
> is superb and it's literally a work of art.  It's a shame these
> beautiful components are no longer crafted.  And, it was a great buy.
> Prior to buying it, I checked it and the capacitance varies from 0.01
> to .04 nF.  Yes, nanofarads.  My plan is to increase the maximum
> capacitance to 20 - 40 nF by changing the dialectric and spacing
> between the plates.  I am building a 3/8" acrylic housing for it.
> Changing the spacers between the plates is simple.  I can even add a
> few more plates.  Question is what dialectric should I choose that will
> have 500 - 1000 k and good dialectric strength?  Either a gas or liquid
> dialectric would do or even application directly to the plates is a
> possibility.  According to R. Hull's recent post capacitance resides in
> the dialectric only, rather than the plates.  Maybe this is a place for
> Kristin's XeS6 or what ever that dialectric was.  Any thoughts?
> I cannot find the recent posting of modern dialectric constants and
> their strengths.  Would someone please repost it publically or
> privately?
> Thanks,


You will not find a suitable dielectric to do what you want.  Only barium 
or strontium titanate offer a possibility and you can't obtain these in 
sheet form.  There are just no real dielectrics in the K=1000 range other 
than these special ceramics!!!  Plus, the voltage standoff of these are 
terrible!!!  About 50v/mil!!

Richard Hull, TCBOR