One of my ceramic glass composite sample permittivity increases with increase in frequency (1 MHz to 1 GHz). It shows sharp increase from permittivity 35 to 45.
measured at room temperature.
Glass composites of specially Rare Earth Based (Neodymium Oxides) exhibits this tendency
The conditions of the quasi-stationary electric field distribution in the sample are not valid, i. e. the electric field is nonhomogeneous in the sample and the capacity loses its meaning. The permittivity cannot be calculated from the static capacity. See: p. 35 in the book by Jonas Grigas "Microwave Dielectric Spectroscopy of Ferroelectrics and Related Materials" (Gordon & Breach Publishers).
it depends on porosity and defects of you materials.
also the phases formation of you material can affect this property. however the sinterring temperature of your material could be responsibal of this.
Usually at higher frequency (>1MHz) the dielectric constant remains same. This property is the crucial for electronics circuits (packaging).
In general, the dielectric constant with its two components (real and imaginary) change against frequency. This change depends on the applied frequency range. You can review papers of Jonscher and also F.A. Abdel Wahab (Journal of Non-Crystalline Solids 355 (2009) 2239–2249) (J Mater Sci (2014) 49:720–728) (J. Phys. D: Appl. Phys. 39 (2006) 190–195)
Thank you all for suggestions and advices....Finally I find out a sharp resonant peak near to the 2 GHz. This resonant peak dominant in the impedance analyzer (agilent impedance analyzer) measurement at higher frequencies. (1 MHz to 3 GHz).
Once again thank you all.......
This resonant peak is a result of nonhomogeneous electric field distribution in a sample, i. e. it is not related with the real permittivity of material and it's frequency dependence. This is described long ago in the book by Jonas Grigas "Microwave Dielectric Spectroscopy of Ferroelectrics and Related Materials" (Gordon & Breach Publishers).
Thank you very much Prof. Grigas. According to your suggestions, and I read the book "Microwave Dielectric Spectroscopy of Ferroelectrics and Related Materials" It is excellent.....The book help me lot to interpret my results....
Once again thank you Professor.....
Dear Prof. Jobin Varghese
I think that these readings are not true and must be removed.
You have to make a good contact between the sample and the electrode.
what kind of electrode do you use? (4 electrode or 2 electrode?)
Dear Prof. Mohamed Gomaa,
I used platinum sputtering, and I tried point contact as well as probe contact using Agilent impedance analyzer. cross check the result with LCR meter.
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