I would like to ask you what technique did you use to measure permittivity

of ferrites and at which frequency range.

Note that ferrites exhibit magnetic losses that are much higher

than the dielectric ones so one has to be carefull in analysing

mesurement results.

Dear sir

It is measured using LCR meter in frequency range 20 Hz - 2 MHz in room temperature.

With thanks

Chitra

Hi Chitra Devi,

Dielectric loss is a quantity of dissipation of electromagnetic energy. An efficient dielectric supports a varying charge with minimal dissipation of energy in the form of heat.

There are two main forms of loss that may dissipate energy within a dielectric. In conduction loss, a flow of charge through the material causes energy dissipation. Dielectric loss is the dissipation of energy through the movement of charges in an alternating electromagnetic field as polarisation switches direction.

Dielectric loss tends to be higher in materials with higher dielectric constants. This is the downside of using these materials in practical applications.

Dielectric loss is utilised to heat food in a microwave oven: the frequency of the microwaves used is close to the relaxation frequency of the orientational polarisation mechanism in water, meaning that any water present absorbs a lot of energy that is then dissipated as heat. The exact frequency used is slightly away from the frequency at which maximum dielectric loss occurs in water to ensure that the microwaves are not all absorbed by the first layer of water they encounter, therefore allowing more even heating of the food.

APPLICATIONS OF DIELECTRIC MATERIALS:

1. Capacitors which use vacuum,air & gases as dielectrics dielectric losses in these capacitors are very small.Therefore these are used in radio frequency circuits.

2. Dielectric resonators- A dielectric resonator oscillator (DRO) is an electronic component that exhibits resonance of the polarization response for a narrow range of frequencies, generally in the microwave band.

3. Memory Devices

Thank you Dr. Kesava Yellareddy for the nice explaination.

With regards

Chitra

Dear Elangbam Chitra Devi ,

Dissipation of the electromagnetic energy in ferrites at low frequencies is, in my opinion,

mainly related to the magnetic losses (permeability).

Note that for this reason ferrites are used as absorbers of electromagnetic radiation in unechoic chabers at MHZ

frequency range. The imaginary part of permeability, even for low loss ferrites and garnets (such as polycrystalline YIG) ,

at frequencies up to 2 MHz can be several orders larger than the imaginary part of permittivity (or the dielectric loss tangent).

I think that what you measure as the loss factor employing the LCR meter is a combination of magnetic, dielectric and conductor losses.

Have a look into the paper: IEEE Trans. on Magnetics, 32, pp.1924-1933, 1996 to see how magnetic properties of garnets

vary with ferquency.

Thank you very much Dr Jerzy Antoni Krupka for the detail explaination and the source provided.

Dear Elangbam Chitra Devi,

could you display a Nyquist plot, from your measurements, including many[1] points near the peaks[2], particularly, at the high(er) frequencies[3] ?

1. Many N (or even the maximum M available) Z-measurement points per band (N>10000).

2. Your note : "dielectric loss tangent peaks".

3. At high frequencies, the Capacitive (C and, maybe, the R) impedance parts reduce, and an inductance part (jLω) might be shown, as a small Z-loop in a Nyquist plot, near your peaks[2].

Dear Dr Ioannis Samaras

Thank you for the kind response. Please see the attached graph in which the shifting of peak appears for a sample processed under different parameters (sintering temperature).

With best regards

https://www.lehigh.edu/imi/teched/JapanWS/WS11AB_Lanagan.pdf

Thank you so much Dr Hamit for the nice contribution. It is very useful for me.

With best regards

I agree with Prof.Krupka.

What is the important information that can derived/ concluded/ extracted from the loss tangent peaks? and how and where it can be utilize in applications?

• If dielectric loss is more in the mentioned frequency range( 20 Hz - 2 MHz ), those material can be used in EMI filters.
• If it is less, measure in microwave region and find applications in circulators, isolators, phase shifters. etc.,