Hi!

If you can remove the piezo, I can only suggest attaching a FR4 insulating layer before gluing it (Flame Retardant Type 4 glass-reinforced epoxy used generally for integrated circuits boards). Also, you might experience an electrical breakdown at those high voltages.

An idea is to apply voltage on the outside electrode, more far from the plate you have glued it too. If you applied on the closest electrode (attached to the plate), the voltage might go through it. Having terminal up and ground down on the plate would make the voltage pass through piezo only and discharge through ground.

Also, I am attaching a handbook. It says: "The highest value of generated electric field is determined by electrical breakdown occurring either through the body of the piezoceramic sheet or over the its edges. Debris adhering to edges can initialize edge discharge at fields as low as 400-800 volts/mm. Continuous breakdown occurs around 3,000-4,000 volts/mm, usually at impurity or defect regions within the bulk of the material. This can lead to a short circuit across the sheet" (p. 38).

I don't know if you applied a DC or AC voltage... "Silver electrodes are not recommended for high electric field DC applications because silver ions are likely to migrate forming a bridge between the two electrodes, which is a resistive short circuit. Silver electrode piezoceramic is, however, often used in AC applications." (p. 62).

That's all that I could think of and find...

Best of luck!

Claudia

I may suggest a simple thermo glue (from the glue gun). At least I have used it very successfully when was modifying the electrical machine's windings.

Adding to Claudia's and Konstantin's answers, I'd recommend selecting a glue/adhesive that has a dielectric strength (if such data is available from the glue/adhesive manufacturers) above 5kV, say 5.5kV to 10kV and the glue must reject any moisture from diffusing through to the inner regions of the dry adhesive. Moisture infused throughout the glue's molecular matrix would de-rate its dielectric strength.

Some formulations of epoxy resins, over time, do absorb moisture, weakening both their mechanical bonding properties and their dielectric strength.

What may be required is a fire retardant, water/moisture (including possibly chemical) resistant adhesive with a high dielectric strength, able to bond between the coating material (CFRP laminated composite) of the piezoelectric patch and the material of the target surface. The adhesive should also maintain bonding strength over an expected operating temperature and relative humidity range.

In the event that data on dielectric strength is not available, the solution may be to obtain a calibrated dielectric strength (aka withstanding voltage) tester, select a shortlist of the best adhesives (including perhaps those used in marine applications) obtain Copper foil and whilst wearing a pair of clean powder free nitrile gloves (to avoid contaminating the cleaned surfaces with hand skin oil or perspiration) clean any oxide residue and then after the Copper foil has been cleaned and dried, replace the nitrile gloves with a fresh pair and cut the foil up into squares or rectangles (depending on the piezoelectric actuator's form factor) to the same size as the piezoelectric actuator's surface area, and also obtain a piece of material of which the target surface is made and also clean it (using and replacing nitrile gloves as needed) and cut it up into squares or rectangles a bit larger in surface dimensions than the piezoelectric actuator to leave sufficient room for enabling a good contact surface (completely free of any adhesive or its residue) for the dielectric strength (aka withstanding voltage) tester's negative probe.

Whilst cutting up the Copper foil and target material, take care to make sure fingers and hands are kept clear from sharp edges and corners. A good idea may be to cut up a few extra pieces of Copper foil and target surface material, to have spare pieces readily available if some part of the experiment doesn't go as planned.

List the name for each adhesive (if two or more adhesives have the same name, add a manufacturer part number/reference and the brand name for each adhesive) to be dielectric strength (aka withstanding voltage) tested to a table of results and add a column with an unique single letter or number identifier for each adhesive sample.

Next wear another pair of clean nitrile powder free gloves and clean each square or rectangle of both the Copper foil pieces and the pieces of target surface material, with high chemical purity isopropanol or isopropyl alcohol to remove any remaining moisture or dust, then store the Copper and material pieces separately in clean and dry containers with doors or lids closed to protect the pieces from the environment.

After waiting for the alcohol to dry always carefully (to avoid cuts) handle each square or rectangle of the target material by the edges only (to avoid contaminating the cleaned surfaces) uniquely label on one side, a single number or letter identifier for which adhesive will be applied (if the dielectric strength (aka withstanding voltage) tester's negative probe has an alligator/crocodile clip avoid writing over the area where the opposite jaw of the clip will clamp on), then immediately on the opposite side apply a sample of enough adhesive to match the piezoelectric actuator's contact surface area, leaving an adhesive free area for the dielectric strength (aka withstanding voltage) tester's negative probe to be clamped.

Two sets of samples for each adhesive may be prepared, one with an added piece of FR4 insulating layer cut to the shape of the piezoelectric actuator (the same adhesive should be used to glue the FR4 to the target material piece) and another sample without the added piece of FR4.

For each adhesive sample place one piece of Copper foil (oriented to match up with how the piezoelectric actuator would be placed) on top of the adhesive, carefully making sure to remove any air bubbles and taking precautions to prevent the Copper foil from sinking into the adhesive, to act as an electrical contact point for the dielectric strength (aka withstanding voltage) tester's positive polarity probe; if the positive probe is also an alligator/crocodile clip, it may be a good idea to have pre-soldered a cleaned Copper tab approximately in the geometric center of the Copper foil to clamp the clip in place. Another reason for the Copper foil piece, is to avoid contaminating the positive probe with any carbon residue if it's allowed to make contact with the dry adhesive. Please don't label the Copper foil pieces.

Carefully place the square or rectangular samples in a clean and dry container or box with a lid or door, to protect them from dust or dirt whilst they dry, remembering to always handle the square or rectangular samples by the edges only. The box should be placed in the driest part of the laboratory, and the laboratory should be well ventilated to draw away any fumes released by the drying adhesive samples.

Writing from my own lab experiences, it's a good idea to take a statistically significant sample of readings for each sample. Depending on time constraints, seven to nine readings should be adequate, and a . The data should then be entered into a spreadsheet and use the built-in statistical functions to find the mean, median and standard deviation.

Whilst the samples are drying, if you've never used a dielectric strength (aka withstanding voltage) tester before, read the manual thoroughly making sure how to operate the instrument correctly and make sure to familiarize yourself with the safety procedures.

Prior to starting any test, wear proper PPE including a suitable face mask with eye and face protection goggles, to keep out any potentialmetal sparks, vapors or chemical fumes from the face, eyes and lungs. Electrical testing should be carried out in a well ventilated area of the laboratory.

If possible, for electrical safety reasons, both test probes should ideally be alligator/crocodile style clips. If the positive probe is not an alligator/crocodile style clip, but a hand held probe, always hold it with your right hand (or if you have the medical condition called Situs inversus of the subtype dextrocardia, where the point of your heart is on the right side of your chest (thoracic cavity), hold the positive probe with your left hand), and always place the fingers behind the finger guard, as far away from the probe's electrical contact point as possible. Your other hand should never touch a grounded/earthed point on the laboratory bench; you may use Nikola Tesla's technique of placing your other hand in a lab coat pocket.

When doing any kind of high voltage testing always comply with the two person rule, where there should be another person working in the laboratory to get you out of trouble in case of an electrical accident, or better still, if the other person has prior experience doing high voltage testing, to supervise and monitor you whilst you perform your experiment.

After each sample has been tested, switch off the power switch installed in the dielectric strength (aka withstanding voltage) tester, and switch off the power switch on the mains power outlet, then unplug the power cord plug from the mains electrical power wall outlet, then if required make sure any internal electrical energy storage capacitors have been discharged completely before swapping for the next sample to be tested.

Sorry to waffle on so much, and you probably know much of what I've written already, but I wanted to emphasize the need to diligently follow proper safety procedures when working with high voltage systems either in a laboratory, or out in the field.

Disclaimer: The above information has been provided as a guideline only, and should never be substituted for appropriately qualified chemical and electrical safety training. I don't accept any responsibility for how the above information is used, or for any injuries or death that may occur if proper industrial safety procedures/protocols aren't implemented.

(1) Your problem due to arcing is related too arcing occurring at the edges of your pzt ceramic, which should be thoroughly clean. Your PZT wafers may be quite thin. Even though you find no short circuit with a simple multimeter (which appplies only a few volts), the problem is severe when you applu high KV.

(2) As you are applying a high voltage (5 KV), I would advise you to immerse your sample in oil., which will prevent arcing. This is commonly done during pzt ceramic poling.

(3) Finally you can always apply you top and bottom electrodes in such a way that you leave 1 mm all around the wafer (top and bottom) near the edges, in this way your electrodes are far from the edges and you can apply your high KV easily, and using oil is the best way out.