They become highly polarized. The dielectric response can also become nonlinear. At some point, the field becomes so strong that free charges are created and you will see arcing. At the voltages you listed, everything should be okay unless you have extremely thin samples.

Thank you, I am wondering what kind of materials would get more polarized. Are there materials which could store more charges without leading to arcing. Is there any criteria or parameter to measure such polarization process.

Don't think of them as storing charges. There are electron clouds surrounding the nuclei. In the presence of an electric field, the cloud is diplaced created a small electric dipole. When this happens, the material is called "polarized." It acts much like a mass on a spring and displacement can become a nonlinear function of the applied field.

Materials with higher permittivity have charges that are more easily displaced. In fact, the permittivity is a measure of how easily they are displaced. The more easily they are displaced, the greater its ability to store electric energy.

For more discussion on this, see Lectures 2 and 3 here:

http://emlab.utep.edu/ee5390em21.htm

I believe you are talking about maximum capacitance. The charge storing ability of dielectrics is limited. Electrolyte capacitors and the so-called supercapacitors, which utilize mobile charges, perform much better. For this you do not even need high voltage of electrical field, only thin double layer.

Or you are interested in dielectric strength, i.e. the maximum electrical field which can be applied to the material without breakdown. Here you need very low conductivity and defect-free structure (e.g. polyethylene, or very clean oxide ceramics).

Thank you all. Have got most of my answers. I was looking for dielectric strength. A means to increase this property or a material with high dielectric strength should work for me. I still have one more doubt. what would happen if a liquid drop(water) is placed over such polarized substrates. will it get polarized as well.

The distribution of field (and thus polarization or displacement vector) can be calculated from the geometry of the electrodes, the material(s) placed in between using the dielectric constant and the conductivity of the constitutents.

water droplet placed over such an insulator surface will feel polarization. If you are placing it in between two electrodes placed over the surface of insulator (rubber),it will start oscillating because of the change in the direction of electrical field after each half-cycle. Finally it will bridge the gap, causing flashover on the surface of insulator.

I am adding some pictures of this process here so as to explain my point.

Here first picture denotes the electrodes placed over insulator surface and water droplet in between of the electrodes.

second picture denotes the process of flashover as i explained.

Could you please mention the article, where these findings were published?

follow this link..

http://ieeexplore.ieee.org/search/searchresult.jsp?newsearch=true&queryText=Understanding+Water+Droplet+Initiated+Discharges+on+Epoxy+Nanocomposites+under+Harmonic+AC+Voltages+Adopting+UHF+Technique

you can measure this and quantify it. If you consider the rubber material in the vicinity as a dielectric that could get charged, the charges associated with this capacitance can be measured through a high frequency response circuit called Partial Discharge test setup. The Partial Discharge phenomenon can be captured through a high speed camera as well. The discharge is usually measured in the ranges of pC and can go up to nC on continues voltage or field application. The dynamic drop test mentioned above is a good example to demonstrate surface aging.

Dear Anil,

your question was not including information on the properties of the high voltage you need to apply to the material. In fact, it makes a huge difference whether you apply DC, 50 Hz AC or higher frequency AC to the insulating structure. In fact, no material is of pure high density meaning there are definitely no voids. The opposite is the case, especially if you think of transitions between different materials, the electrodes and the insulator, for instance. Then, as in case of the water droplet (thank you Lakshya!), a capacitive voltage divider forms in case of applied AC-voltage. This divider leads to a rather high voltage across a void with low epsilor r - and with that to a partial discharge, or dielectric barrier discharge. The properties of this discharge are depending on many parameters, as the frequency of the applied voltage, the surface properties of the surounding material, the gas within the void etc.

Therefore, if you use insulators, it is important to avoid any voids - this applies also to transformer insulation ... 

Right! A lot depends on the time frame. Soon after I started work at NRL, about 1960, I was involved in analyzing data from an exploding wire experiment. The dielectric of the capacitor discharging into a small length of wire was water and was charged to extremely high voltages. This capacitor could hold a charge for some fraction of a millisecond. The charging and discharge took place in a microsecond time frame. The "switch" that prevented early discharge was simply a layer of mylar so when the voltage built up high enough to penetrate the mylar, the discharge through the wire produced a small fireball, the object of the study.

Hi all

What it means when we have a low dielectric constante of ceramic porcelaines, is it a good dielectric material? i mean, it is well known that dielectric materials as perovskite presents a relative permitivity above 2000, they are a good dielectric materials in another hand we talk about ceramic materials which have low relative permitivities they are also considered as insulator...some one can help me to resolve this probleme??

Electrical aging of insulation. It is rather depends on intensity of electrical field than voltage.