indeed Americium or similar substances used in smoke detectors may be used... Although many smoke detectors nowadays are "optical" and don't actually use any radioactive materials at all any more. And of course it will still only be an atomic battery of some type, so the output will drop dramatically as the atoms decay; for longer periods it would be best to use elements with a long halflife, and those are less easy to obtain again. But still, if one can get beta-emitting material cheaply, it might still be a good source of power... Quick grab from my memory banks, if I recall common beta emitters are strontium, mostly the Sr90 isotope, with a halflife of about 30 years (all other Sr isotopes range from a halflife of a couple of days to a few milliseconds and are thus not very usefull in a battery), cobalt 60 with a halflife of something like 5 years (but! this decays into nickel60 emitting 1 beta particle and 2 gamma photons, and the energy contained in the gamma photons is quite a bit more than that of the beta electron, so not extremely healthy to say the least), iodine 129 and 131 (both used in medicine) with halflives of 7 years and 8 days respectively, and tritium with a halflife of 12 years (but this is actually superheavy hydrogen and decays into helium3, which is of course a gas and will probably decrease functionality of any battery).
Of course other types of radiation emission can be used to generate electrical output as well, if we use the radiation to "knock loose" some of the electrons in the surrounding material, which would be quite similar to photovoltaic cells that use normal light to do the same. This however needs quite some shielding material to make sure the radiation doesn't damage living organisms around it, which would probably make such a battery too heavy for practical use, unless of course we build a miniature atomic battery, but then the output would be relatively small again.
As for the electrodes, yes, it seems to me that you may want to rectify the output. Now it doesn't really sound like your "cookie" is producing a clear wave output, but the output does seem to fluctuate somewhat...
Taking into account that tourmaline contains quite some SiO2 itself, and that SiO2 and other silicates are known to have oscillation frequencies directly related to their crystal structure and composition, one might reason that every piece of quartz inside the "cookie" is a tiny oscillating unit, and the "cookie" thus contains multiple tiny oscillators.
Since oscillators just "shuttle" charges "back and forth" and don't care about the direction in which they do so, the "push and pull" on these charges by the oscillator should average out to about zero. The pyroelectric qualities of the tourmaline scraps account for the clear temperature dependant output, but the direction in which the charges are finally "pushed" depends mostly on the relative p-n effect of regions inside the "cookie", I think.
So you could attach simple electrodes to the top and bottom of your "cookie", and attach a rectifying diode bridge to the electrodes, so that a capacitor connected to the diode bridge receives only positive charge on one plate and only negative on the other, then measure the voltage gain in the capacitor... (You know how such a rectifying diode bridge is made, right? To each elecrode, you attach two wires via diodes, one diode allowing the charge to flow toward the electrode, one diode allowing the charge to flow away from the electrode; then you connect both "outgoing" diodes to one terminal of the capacitor, and you connect both "ingoing" diodes to the other terminal. Voila, rectification of waves/fluctuations.)
But you can of course also turn the electrodes themselves into relatively positive and negative layers, indeed by using copper oxide as a p-layer, and so forth. I am not certain if this will rectify all of the fluctuations, but at least if will create a forward bias as long as the output voltage has the right polarisation.
Another possibility is to make the "cookie" in such a way that the relative p- and n- layers are contained within the "cookie" itself.
Obviously, these possibilities range top-down from easiest to hardest to actually implement.
Theoretically the application of hV during the cooling and solidifying stages should generate a p-n bias inside the material already, and up to a point one would expect some relative p-n shifting within the material, causing a slight internal pn rectification already...
A possible problem in ceramics is that, in certain ceramic materials, ions are still free (to a degree) to move through the material, and will do so in reaction to electrostatic and electrochemically induced forces. This may cause a ceramic to seemingly produce output during a certain period, then lose all output after that, because all movable ions have moved and the material is now electrically stable. In certain ceramics heat-driven cycles can occur, which move certain ions up and down a path, which can generate a direct electrical output. This is clearly an ongoing heat-driven electrochemical process, and if I recall correctly such processes are no more than 40% efficient... In other words, it does not look like the direction to persue.
The trick I think is to make a material that allows for a certain degree of free movement of charges, but that does limit this movement to a certain zone, effectively "pinning" the charges to that region, while retaining its crystalline structure. Relative p- and n- "layers" or "zones" should be present in this crystalline matrix, either causing a gradual shift from n- to p-layer over the entire "cookie", or alternating n- and p-layers throughout the entire "cookie", or mixed evenly though the entire "cookie" but with a clear polarisation applied (so all n- layers are oriented toward the positive electrode and all p- layers toward the negative electrode, even though there are no clear "layers" as such).
Additionaly, a path should be provided for electrons to follow, which leads them to and from the p- and n- zones...
What you see happening in the "cookie" you made, where the voltage seems to drop and flip polarity, then build up to a low value again, is to be expected of a material in which the relative p- and n- particles are shifted internally due to the applied electrostatic potential. First, the charges will follow the applied electric field, then when the field is
removed, residual effects of this electrostatic induction and distribution of charges can produce the relatively high output seen. If the material structure is stable enough, the p- and n- particles will remain in their shifted positions (to a degree again), and only when all residual charge has been removed from the material will you be able to see the effect of this p-n distribution as a form of pn-effect.
As for the Casimir effect, I must say Hutchisons mention of the effect surprised me, since I can't immediately determine how this effect could be used in any way to generate electrical ouput... Do you mention it merely because Hutchison does a number of times, or do you have a theory behind it?
The only thing I can think of where the Casimir effect might be usefull, is if we attach the two Casimir plates directly to two very sensitive pieces of piezoelectric material.
The two plates, attracted to eachother by zpe push, will "pull" on the piezo and this will generate a charge on the piezo surface. Of course, since Casimir effect only occurs at tiny seperation distances, the "pull" will be extremely small. Theoretically this Casimir force "pull" becomes exponentially stronger as the distance between the plates decreases. Obviously, the piezo material will have to be able to "stretch" far enough to allow this "pull" to be felt, but not too far as we want the plates to remain seperated from eachother. This is already quite difficult, and we must also remember that the plates need to be extremely flat (on the micro- and nanoscales) and parallel to eachother; needless to say this becomes more and more difficult the smaller we make such plates. Ok, so let's assume we managed to do all this, and the plates are attracted, and the piezo's "stretched" to the maximum. Now of course we want to harness the energy produced, so let's assume we have this setup connected to a simple diode bridge and a capacitor; the charges will flow from piezo surface to electrode (on the piezo) to diode (assuming we have tiny ultrasensitive diodes), to capacitor. Great. Now we have a situation with the Casimir plates closest together as our system will allow, and the maximum charges we can get from that Casimir force extracted through piezo's.
But now, the Casimir plates will stay where they are, because the Casimir force only "pushes" the plates together, and does not provide any mechanism for them to move apart again. To move them apart, we need to "pull" them apart by applying force again. We could apply that force by charging the piezo's oppositely, which will make the piezo's contract, and pull the plates apart. But that process is enthropic again, so the amount of energy we need to input into the piezo's to seperate the plates will be greater than the energy gained from the Casimir effect pulling the plates together...
I fail to see how energy could be extracted on the basis of that effect... That said, it may be worth studying the effect of frequency differences in respect to frequency shielding, which in a way is what happens in the Casimir effect. After all, if the abundance of energy at a certain frequency has a clearly observable effect, then the absence of energy at a specific frequency (or frequency range) may very well have similarly clear observable effects... Especially in the circumstance that said absent frequencies are normally present at relatively high intensities...
And of course perhaps there is more to the Casimir effect than meets the eye... Perhaps on the tiny scales of silicate platelets, the minute differences in chemical composition of these platelets may cause them to "feel" slightly different "pulls", or even cause the electrons inside them (or on their surfaces) to move about according to a certain frequency which is "seen" by both Casimir platelets, but not by the surrounding material, thereby generating an unknown "Casimir oscillation"... That might increase the overall oscillatory action of the material and might support electron flow mechanisms.
It is also possible that the tiny platelets act as tiny capacitor plates, the quartz as tiny oscillators, and the other elements as p- and n- material layers, thereby turning the entire "cookie" into a big heap of fairly randomly organised and minuscule LC+rectifyer circuits. Aligning those accoring to the right 'polarity' would allow for (part of) the resulting charges/currents to be directed to either "pole" of the "cookie". This sounds cool, but also seems to be the least likely interpretation.
So you see, there are some possible views on how these "Casimir" 'platelets' may or may not be connected to energy generation in such a 'cell'.
I'd like to hear your thoughts on this.
Ian, I have not heard of material becoming radioactive in a Tesla coil as such...
I have heard of unstable isotopes reacting to hV discharges by showing stimulated decay, and also of them fusing during such a discharge.
I suppose it may be possible to take a slightly unstable, metastable, or perhaps even truly stable particle and hit it with hV so hard that it gets knocked senseless and becomes unstable and emit radiation...
Why? Are you thinking of blasting some material with your TC in order to make them emit beta-particles?
If you want to do some hV experiments that may yield higher output, I can suggest a few... But they're totally unrelated to this thread though.