Barium Titanate Capacitor (BaTiO3)

This was barium titanate mixed with mineral oil and sandwiched in wax. The idea was to apply high voltage DC across it and test for weight change. None was detected. I didn't measure dielectric constant. Click on the photos for larger versions.

This was barium titanate mixed with paraffin wax and placed in a flat, square box-like mold to make a flat plate capacitor for doing a propulsion test. A relatively good K of around 12.5 to 18.6 was gotten. Mositure was an issue here, resulting in low resistance through the resulting dielectric.

This was an effort to get rid of the moisture issue found in the above experiment, a 1/8" thick layer of barium titanate powder was placed in a 6" x 6" mold and baked at 250F for about an hour. We then confirmed > 20Mohms through the powder. Next, 95F paraffin wax was poured over a spatula onto the powder in the hopes it would sink in everywhere. The result was the bubbly mess in the rightmost photo.

This was a propulsion test for a high K dielectric done by connecting 10 barium titanate doorknob capacitors in parallel. The result was placed on a digital and power using a high voltage power supply. No weight change was detected up to around 59.5kV when breakdown occured around one of the capacitors, but not through it.

This was a failed attempt to make a cylindrical capacitor. It failed for two reasons. This first was that the mold was not circular. It was made of a sheet of acrylic rolled up into a cylinder. Doing so inevitably leaves an overlapped length inside that does not follow the curve of the cylinder. The second reason it failed was that the dielectric constant was only 3. When the mix of barium titanate powder and liquid epoxy was made, the result in the mixing container was a thick sludge at the bottom which contained mostly barium titanate and a white liquid at the top which contained mostly epoxy. As the third photo shows, I used the epoxy rich but barium titanate poor liquid by dripping it into the mold. This resulted in a dielectric made mostly of the low dielectric constant epoxy.

This was another failed attempt to make a cylindrical capacitor. It failed for much the same reason that the previous attempt did, the dielectric constant was too low and for much the same reason. I was aware from the above successful flat plate capacitor made back in September 9, 2004 (K=12.5 to 18.6) that I wanted the thick barium titanate and wax sludge but as soon as I tried to push some down into the cylinder, it cooled and hardened. It happened too fast for me to pack it in properly. So then I quickly removed the mess and put my mixing bowl itself on the stove. I brought the mix to a boil, hoping that would cause a lot of barium titanate to mix well with the wax. I then poured that into the cylinder as a liquid. But if you look closely at the photo you'll see that the thick sludge is still in the mixing bowl while I'm pouring in the liquid which is still mostly wax. The result was a dielectric constant of only around 2.

This was my first successful barium titanate cylindrical capacitor, one with a decent dielectric constant of 15. It was a mix of 80% barium titanate and 20% epoxy. The key was to push the sludge down into the cylinder and tamper it (pound on it with a blunt stick) to pack it in. The curing time on this epoxy was over 20 minutes so I had time to do this process, unlike with a wax sludge which hardens almost instantly on contact with the cylinder walls.

I wanted to see if barium titanate powder by itself would give a high dielectric constant. However, since my outer electrode was to be a mesh I had to keep the powder in a plastic cylinder so the plastic cylinder's low dielectric constant also contributed to the result. I got a dielectric constant of just 5. I don't think this low value had to do with the plastic cylinder alone but was also due to air trapped in with the barium titanate powder, air having a K of just 1. I feel this way because in my April 15th capacitor above I did one test with the much thicker walled mold still on and got a K of 6. I know I tamped the powder in fairly well because when I later removed the copper rod to remove the powder, the powder held its form within the plastic cylinder.

Since working out the process, I've made a few cylinders using the same mold as in the April 15, 2010 entry above. But this time while mixing the barium titanate and epoxy I kept cutting it into smaller and smaller pieces, repressing it together, cutting again, and even added more powder at one point. I ended up with mostly 1mm or smaller diameter balls with 86% barium titanate. I dropped them into the mold a little at a time and tamped (pressed) them down firmly before dropping in more. The result was a K of 27!