# Dielectric constant for aliminium nitride

1. Feb 17, 2009

### sallyishyper

I know that a dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability. or in english terms: A dielectric material is a substance that is a poor conductor of electricity, but an efficient supporter of electrostatic field s. If the flow of current between opposite electric charge poles is kept to a minimum while the electrostatic lines of flux are not impeded or interrupted, an electrostatic field can store energy. but im not entirly sure what this value means or represents. i dont think ive understood the concept properly, its entirely self taught:

constant for aliminium nitride is 0°C 8.9 at 1MHz
can somebody explain this please, i have no idea what it means
thankyou

2. Feb 19, 2009

### lightarrow

It means, among other things, that if you construct a condenser with that material as a thin layer between two metal plates, the condenser's capacity (charge per unit voltage) is: $$\epsilon S/d$$ where $$\epsilon = \epsilon_0\epsilon_r$$ and $$\epsilon_r$$ is your 8.9. S is the area of the metal plates and d their distance (the material's thickness). It depends on frequency (if you want precision) because the polarization depends on it (for very high frequencies the charges don't have the time to separate into dipoles so the dielectric "constant" decreases).

Another way to consider it is to notice that the electric field is reduced by $$\epsilon_r$$ inside the material.