DIY Barium Titanate Matrix

Maybe some useful info in this:

Supposedly, the best you can do with iron filings in epoxy is a relative permeability of about 10. The situation is slightly better for electrostatics, since the epoxy has some permittivity itself (~4?). But this still pales in comparison to the k ~= 10k of pure barium titanate.

In short: you'll get very little electric field across the individual grains. Most of the voltage will be dropped across the thin layers of epoxy inbetween. Therefore, the piezoelectric effect will be correspondingly small.

The best powdered iron cores are resin-bonded under ideal conditions (optimal amount of resin, pure materials, correct particle shape and size distribution, and pressed under high pressure). Possibly with the help of an hydraulic press, you'll get something close to maybe k = 400. That's still only ~2.5% of the full rated value. If that's still good enough, then sure, you should be able to hack something that works.

Ferrites, like ferroelectrics, must be very high purity and fired to high density in order to obtain the highest values (mu_r ~= 15k for the best ferrites, and something like 20k for dielectrics).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

"Bill Kennedy"  wrote in message 
news:4cc77aee.10001500@news.tpg.com.au...
>I want to conduct some experiments with the piezoelectric
> (ferroelectric) properties of Barium Titanate.
>
> Since I only have the powder, and cannot afford to have it fired into
> a ceramic, is there any type of commerical filler or bonding agent
> that I might add that would allow me to simulate, at least to a
> degree, the effects of a genuine ceramic?
>
> Thank you for any suggestions..
>
> Bill Kennedy

Go to a pottery class or store..

Your best bet may be to talk nicely to a local university or someone that has a ceramic powder press and a flame that will reach >1650C. I can't see the result being worthwhile though since the crystals in the powder will all have a random orientation.

Might be easier to buy a piece already in the right form from one of the educational suppliers. Try asking in sci.chem there may be eutectic tricks to lower the melting point to something a hobby kiln can handle.

Regards, Martin Brown

Do you plan on polarizing it? I seem to recall many kilovolts used to polarize, and I think? the temp was raised and allowed to cool while under HV stress. Can't you buy what you need? MikeK

This might interest you:

The EEStor patents cite a journal article[28] and a Philips Corporation patent[29] as exact descriptions of its "calcined composition-modified barium titanate powder." The Philips patent describes "doped barium-calcium-zirconium-titanate" (CMBT) and reports a permittivity of up to 33,500 at 1.8 V/?m, but does not report the permittivity at high electric fields such as the 350 V/?m EEStor claims. EEStor coats its

0.64 micrometre (average size) CMBT particles with 10 nm aluminum oxide (8% by volume) and immerses them 4% PET plastic by volume, giving 88% CMBT. The patent claims the aluminum oxide coating and PET matrix reduce the net permittivity to 88% of the CMBT permittivity. The Philips patent did not use either aluminum oxide or PET. The dielectric in solution is screen-printed and dried in 10 ?m layers, alternating with 1 ?m aluminum plates (used to apply the working 3500 V).

A July 2008 press release states the PET plastic matrix allows for better crystal polarization and that this "along with other proprietary processing steps provides the potential of a polarization saturation voltage required by EEStor, Inc." The patent states this is done at 180 C with 4000 V.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show

I still haven't found specifics. I did get the below from;

The domains in a ceramic element are aligned by exposing the element to a strong, direct current electric field, usually at a temperature slightly below the Curie point (Figure 1.2b). Through this polarizing (poling) treatment, domains most nearly aligned with the electric field expand at the expense of domains that are not aligned with the field, and the element lengthens in the direction of the field. When the electric field is removed most of the dipoles are locked into a configuration of near alignment (Figure 1.2c). The element now has a permanent polarization, the remanent polarization, and is permanently elongated. MikeK

Here's a pdf that gives 4kv/ 0.1mm

And suggests the following ( which is way more than I know) "Termination of the increase of piezoactivity is due to the decreased ef?ciency of the polarizing ?eld because of it being shielded by a space charge accumulated in the near electrode areas and because of the increased conductivity of the materials."

Somebody that makes good Ales.

Chimay is a good one.

Wait... those are Monks.

Oh well... God gets praise in both cases.