In my sample the dielectric constant increases with an increase of the frequency. But this happens only for a small temperature range. Below and above that temperature range it decreases with an increase in frequency.
Dear Parveen kumar,
In general, as frequency increases, the material’s net polarisation drops as each polarisation mechanism ceases to contribute, and hence its dielectric constant drops. but in your material exhibit different way that may be only low temperature. Many materials, possess permanent dipoles, there is a significant variation of the dielectric constant with temperature. This is due to the effect of heat on orientational polarisation. However, this does not mean that the dielectric constant will increase continually as temperature is lowered. There are several discontinuities in the dielectric constant as temperature changes. First of all, the dielectric constant will change suddenly at phase boundaries. This is because the structure changes in a phase change and the dielectric constant is strongly dependent on the structure. Dielectric polarization in nonconductors has mostly two causes, namely electronic polarizability (electrons shifting within molecules) and orientational polarizability (dipolar molecules rotating or flipping, or ions changing places). The first effect has a rather weak temperature dependence, the second a rather pronounced one. In a polar medium, high temperature disturbs the alignment of dipoles in an outer field: the dielectric constant decreases with temperature. In a ferroelectric medium, the dipoles are already aligned and, unless the outer field is very strong, thus do not contribute to the orientational polarizability. High temperature disturbs the ferroelectric alignment and produces molecules that are free to reorient in an external field, and these contribute to the dielectric constant. Well, this is a kind of very simplistic explanation, but it may give you an idea which forces are at work.
Dear Parveen kumar,
In general, as frequency increases, the material’s net polarisation drops as each polarisation mechanism ceases to contribute, and hence its dielectric constant drops. but in your material exhibit different way that may be only low temperature. Many materials, possess permanent dipoles, there is a significant variation of the dielectric constant with temperature. This is due to the effect of heat on orientational polarisation. However, this does not mean that the dielectric constant will increase continually as temperature is lowered. There are several discontinuities in the dielectric constant as temperature changes. First of all, the dielectric constant will change suddenly at phase boundaries. This is because the structure changes in a phase change and the dielectric constant is strongly dependent on the structure. Dielectric polarization in nonconductors has mostly two causes, namely electronic polarizability (electrons shifting within molecules) and orientational polarizability (dipolar molecules rotating or flipping, or ions changing places). The first effect has a rather weak temperature dependence, the second a rather pronounced one. In a polar medium, high temperature disturbs the alignment of dipoles in an outer field: the dielectric constant decreases with temperature. In a ferroelectric medium, the dipoles are already aligned and, unless the outer field is very strong, thus do not contribute to the orientational polarizability. High temperature disturbs the ferroelectric alignment and produces molecules that are free to reorient in an external field, and these contribute to the dielectric constant. Well, this is a kind of very simplistic explanation, but it may give you an idea which forces are at work.
Dear Parveen Kumar,
Could you explain me what material you are working on? Assuming that you have done your measurements correctly, your observation answers your own question with yes. But it is not what you would expect indeed. Normally motions (also dipole motions) have a certain inertia and above a certain frequency the oscillatory motion is damped.
An increase in dielectric constant with frequency would mean that the friction against dipole motion drops with frequency. Let us speculate about this. Assume that the friction of the dipole motion is due to molecular rearrangements of the environment. In case that the timescale of these rearrangements is slower than the timescale of the dipole motion, the friction will indeed be less at higher frequencies. But to be honest, this is pure speculation and first more info about the material has to be given.
Dear Parveen Kumar,
You didn't mention which type of material is it. Further whether the increase in dielectric constant with frequency is with increase in temperature or decrease in temperature? What is the temperature range, etc. is not clear.
Dielectric permeability decreases with frequency increase. Opposite to that, conductants of dielectric increases with frequensy. See MAXWELL - WAGNER model of dielectric in
WIKIPEDIA.
No way you can explain increase of dilectric permittivity with frequency. There seems some problem with the measurement. If you provide complete dielctric spectrum, measuring instrument and cell configuration only then you may get proper feedback which may help to resolve the issue.
Increase in the apparant value of the dielectric constant (permittivity) may be due to various parasitic effects. It must not be confused with real increase in the value of thedielectric constant of material. In the attached paper you can see one of the cause of increase in the dielectric constant due to parasitic effect with increase of frequency. Similar parasitic effects are observed in the low frequency region as well.
Ms Kumar,
I like V. Jayaramakrishnan's general explanation (and the others' were helpful, too). At higher frequency, the electronic contribution to polarizability should stay high while heavy-ion and heavy-atom contributions should decrease. But this brings up Hongbo Liu's question: In what frequency range do you see permittivity increasing? You can sort of "calibrate" your mind's frequency meter by looking at the hypothetical spectrum from dielectric spectroscopy given on this web page:
http://en.wikipedia.org/wiki/Permitivity
(I think the spectrum will be the second figure.)
Dear Parveen kumar
The dielectric constant is about Molecule but frequency is about bond therefore there is not direct relation between of them
Typically, the frequency increases with decreasing dielectric constant. If a certain temperature range with increasing frequency permittivity increases, it may be due to structural changes (or transitions) in this area.
But structure can not change with frequency at a constant temperature. It will change only if temperature is being changed. If latter is the case then there are several other reasons as well.
Dear Parveen Kumar,
Could you detail the temperatura range and the frequency used?
That phenomenon is presented in state change of foods specially at low frequencies.
Dear Perveen,
First of all I will appreciate and regard your question and the useful views of good people. These views and explanations are really useful and represents the comprehensive understanding about the frequency dependence of the dielectric constant. In my opinion, many things are important in your case. Initially, the frequency range. whether the effect is seen in KHz, MHz or GHz range. Since, different electric dipoles have different relaxation frequencies. secondly, the conductivity of your sample. if the sample is dominated by localized charge carriers or itinerant conduction is dominant? Thirdly, if the frequency dependence is for wide frequency range i.e more than one order of magnitude or narrower?
regards
This may be a rather simplistic answer or comment, but as far as I know the value of static permittivity (the new name for the old dielectric constant) remains constant in a frequency range that depends on the size of the compounds molecules. This constancy stops when relaxation starts and there is a drop in value as the frequency increases. At least this is what is shown in the typical graph of permittivity vs log of frequency that appears in every textbook. The reason for this behavior is, of course, among the many detailed comments listed above.
Hello, Praveen Kumar.
We know that dielectric material becomes polarized in an applied electric field. for the material to become polarized, some time span is needed to orient the dipoles according to the direction of applied field. this time span is called 'relaxation time'. (probably in the range of picoseconds), so if the direction of applied field changes nearer to 8GHz and above, the dipoles inside the material may not able to reorient themselves at this frequency, and hence at higher frequencies, the dielectric constant drops down. The dielectric constant also depends on the structure, as the phase changes the dielectric constant also changes (suddenly at phase boundaries). For your case, may be the temperature factor is affecting the phase at particular temperatures hence such effect may be observed.
In order to give a satisfactory answer to this question, one must know what is this material to find out which polarization mechanisms is effective. In case of ionic polarization, the dielectric constant increases with frequency before resonance, then it peaks at resonance and decreases again at frequencies above resonance. In case of orientation polarization the dielectric constant decreases with frequency. At extremely high frequency the electronic polarization is dominant where it behaves with frequency like the ionic polarization. Therefore, it is important to show the range of frequencies of your measurements. In addition one has to be sure for the correctness of the measure nets. also, one has to consider the effect may be due to specific structural change in the material as you change the temperature.
Best wishes
In my opinion, the permittivity increase with frequency has been considered as an unexpected or questionable behavior. This is because strongly polarization dependent and the total polarization arising from electronic, ionic, dipolar and space charge polarization show a decrease as the frequency increases. Such unexpected behavior could be obtained at very high frequencies of the measuring technique as an experimental errors.
regards
What material is under study? Normally, the permittivity decreases with the increase of frequency. The type of material may help to explain this particular explaination.
Correct your English??? There not their........ Then suggest your answer???
structure not change with frequency at a constant temperature. It will change only if temperature is changed.
Normally, dielectric constant should decrease with frequency at constant temperature; until there is structure change ( the chance is minor) or some resonance.
dielectric constant should decrease with frequency at constant temperature reasons what are the reasons,
Dear Asghari Maqsood
I also observe experimentally this effect in my samples based carbonaceous material/silicon in room temperature and frequency range between 8.2-18GHz... Have you got any current reference to indicate about the permittivity changes in function of frequency and in constante temperature?
To: Meritorious Professor & Professor Emeritus, Dr. Asghari Maqsood
A stored energy of a suitable substance should remain constant if it is in isolation. Isolation means that substance should also deal no effect of temperature and pressure from the surrounding environment in addition to usual connection of determined input source. For that substance, variation of temperature in a small range is considerable under the execution of localized structural dynamics at atom and electron levels. So, a decrease or increase of dielectric constant of that substance (by decreasing or increasing number of cycles per second respectively) is associated with intrinsic characteristics. Below and above that small temperature range (dielectric constant decreases with an increase in frequency), this is either a question of capability (intrinsic characteristic) of substance to do work in such manner or a question of reliability/certainty of measuring set up under such conditions. Finally, both (substance/dielectric material and setup) stand as a material. A quantity measuring the ability of stored energy of a dielectric material or substance is referred as dielectric constant, which is because of the heat energy or photon energy or both.@
@miguel Angelo. Our paper appeared in Journal of alloys and compounds 509(2011)6649. There we observed this type of variation in dielectric constant.
I guess your material shows resonance at the specified temperature
Dielectric constant decreases with increasing frequency. Please see article G.A. Khater et.al. entitled "Dielectric properties of basaltic glass and glass-ceramics: Modeling and Applications as Insulators and Semiconductor
I think you have to check the material of the used electrode holder to be non-polarizing and minimize its sharing effect (resistivity should be less than 0.5ohm).
In addition, this phenomenon is usually noticed in Hioki LCR Hi Tester@ It may be a technical problem.
Parveen Kumar My recommendation is to change the electrodes and the used bridge and to check the presence or absence of this effect
For most dielectric materials such as glass, polymer, metal oxides, ceramics, etc., the permittivity (dielectric constant) decreases with increasing frequency due to decreasing the total polarization components, i.e. space charge, dipolar, ionic and atomic. On the other side, for specific ferroelectric materials, the permittivity found to be slightly increased in the frequency range of 100-950 MHz. For instance, the permittivity of Barium Strontium Titanate (BST) slightly increases as the frequency increases and reaches its maximum value at 950 MHz, then considerably decreases upon increasing the frequency just above 950 MHz. For such a case, 950 MHz is called a relaxation frequency (fR) characterizing BST material. The occurrence of such behavior in so many ferroelectric materials, is in fact associated to the polarization of domain wall.
For more details, you can have a look at the following references:
1. J.D.S. Guerra, J.A. Eiras, J. Phys. Condens. Matter 19, 386217 (2007)
2. M. Maglione, R. Bo ¨hmer, A. Loidl, U.T. Ho ¨chli, Phys. Rev. B 40, 11441 (1989) 45. G. Arlt, N.A. Pertsev, J. Appl. Phys. 70, 2283 (1991)
3. J.D.S. Guerra, OP Physics 4, 1 (2009)
To: Meritorious Professor Dr. Asghari Maqsood,
Increasing or decreasing a specific parameter to determine a property of substance/material remained a central one in scientific research and it will be, but the current scenario demands a deeper insight where more than one parameter should simultaneously be looked for. As said in the previous communication, an intrinsic nature of material is crucial along with the external input sources. Their separate study is also important, so do the structure and measuring setup. Below and above that temperature range, it might be the case that orientation of electrons permanently aligned in the atoms of specific element, which is in such manner that the electrons favor to decrease dielectric constant with an increase in frequency throughout. By the way, this should be related to dielectric behavior rather than dielectric constant. The orientation is vital to understand the behavior of structure at atomic level, so at nano and micro scales (https://doi.org/10.26434/chemrxiv.11553057.v3).
Within a small temperature range, dielectric constant of sample increases with an increase in the frequency, which is under the unfavorable attained orientation of electrons and so for atoms, too. Below/above the specific temperature range, dielectric constant of sample decreases with an increase of the frequency, which is due to favorably attained orientation of electrons. Please note that temperature variation stores the heat energy in sample accordingly, thus influencing the structural hierarchies for the set duration. Heat and photon energy phenomena (https://www.preprints.org/manuscript/201701.0028/v10) and propagation of photons through photonic band gap (https://arxiv.org/abs/1611.05392v23) can be helpful.
Moreover, RSM software & real time analyses may present advanced information and broader insight of the problem.
Dear Dr Girish Wadhwa, I have watched your presentation and thank you for sharing this. This is quite a good effort as long as it is a matter of programming behind the tool. However, presented theory is based on the conventional knowledge for which we are familiar. This requires to amend developing intriguing thoughts in the programming behind the tool as well. By the way, how you differentiate b/w mechanical signals and electrical signals? How you manipulated these (mechanical and electrical signals) in developing the programming of your tool? What are they adding towards developing new insights with relevance to materials of different significance (dielectric, magnetic, etc.)? Please take some in this regard and I will be happy to interact with you on these endeavors.
From my experience working with dielectric properties including dielectric constant in detecting the Basal Stem Rot disease in the leaflets of the oil palm trees, I found that the normalized dielectric constant values were found to decrease with an increase in frequency.
Dear Praveen,
Yes but condition applied.
Frequency
Dielectric constant of a material changes with frequency. In general, as frequency increases, the material's net polarisation drops as each polarisation mechanism ceases to contribute, and hence its dielectric constant drops. But if your material exhibit different way that may be only low temperature. It is found that with increasing temperature dielectric constant increases. It is clear that the value of dielectric constant decreases up to 104 Hz and beyond this it increases. Generally, a dielectric loss decreases with increasing frequency.
Summary-
The dielectric constant (ε′) decreased rapidly with the increase in frequency. This decrease is due to the reduction of space charge polarization effect. Then, it remained nearly constant but, increased with increasing temperature at a given frequency. However, at low frequency the dielectric constant is high.
Various Factors
The dielectric constant depends on various factors such as temperature, intensity and frequency of electric field, humidity, radiation effect, mechanical stress etc.
Effect of thickness
The dielectric constant increased with the increasing film thickness, while the dielectric loss can show a non-monotonous variation. The change in the dielectric constant can be attributed to the dead-layer effect.
Effect of temperature
For materials that possess permanent dipoles, there is a significant variation of thedielectric constant with temperature. This is due to the effect of heat on orientational polarisation. However, this does not mean that the dielectric constant will increase continually as temperature is lowered.
Owing to thermal expansion, the ration of the number of molecules to effective length of dielectric decreases when the temperature increases. As the temperature increases, the orientation of dipoles is facilitated and this increases the dielectric constant.
Hope it is helpful for you.
Ashish
Dielectric constant is frequency dependent and temperature dependent property. When the temperature is increased and the dielectric constant decrease, it means degradation in dielectric response can be possibly due to the incomplete polarization caused by thermal energy. At elevated temperatures, scattering dipoles can not proceed
at high frequency, and therefore lead to decrease in dielectric constant. You can further read the attached article for details.
New insights can be explored by discussing a dipole in a different manner: positive charge with gravitational force, which functions along the south-sided tips of the electrons in bound atoms of dielectric material and negative charge with levitational force, which functions along the north-sided tips of the electrons. The term “degradation” can be changed with “breakoff” (or abrupt decrease in the behavior of dielectric) as it relates more in the areas of biochemistry, biotechnology and biodiversity, etc. Polarization can be considered in the sense of ‘functioning’ of controlled (levitational and gravitational) forces for electrons of bound atoms. Electrons belonging to outer rings (not shells or orbits) in bound atoms deal with greater influence of functioning forces for them as compared to electrons of inner rings. A basic insight reporting atomic structure different to the conventional insights in non-peer review can be referred at link https://www.researchgate.net/publication/323723379 and for only carbon element is at https://www.preprints.org/manuscript/201801.0036/v10. So, a mechanism of influencing forces as per involved energy can be explained. A functioning force in controlled manner for electrons of atoms exhibiting the features of (dielectric) material is by means of action of (thermal) energy (supplied under the various means). Further, it is also thought on that: how the composition of atoms belonging to different elements preserve the feature of their material known in ‘dielectric’ behavior where energy remains stored for a long period of time.
In general, as frequency increases, the material’s net polarization drops as each polarization mechanism ceases to contribute, and hence its dielectric constant drops. But in some cases, at very low frequency look like increase due to electrode problem. Overall, you can see dielectric constant decreases with increasing frequency.
You must understand one main reason why we care so much about dielectric constant is that it changes phase velocity.
1. In actual PCB, there is always surface roughness between dielectric and copper foil which also drops phase velocity, it is more obvious in higher frequencies due to the skin effect, therefore, your circuit doesn't behave at material's bulk permittivity (z-axis permittivity), it always behaves higher than its bulk permittivity, and higher the higher. That's why Rogers recommends design dk=3.04 @77GHz for Rolled copper which is smoother, and design dk=3.16 @77GHz for ED copper which is rougher.
2. I think there must also be some other reason as in my simulation on ring resonator with no roughness material, it also behaves higher at higher frequencies.
To my understanding, the temperature remaining constant, the dielectric loss appears to increase with increase in frequency. It is because if the frequency of the incident wave is too high (i.e. the time period small- smaller than the relaxation time of the dielectric), the dielectric needs more time to respond to the incident field. So, the dielectric polarization does not take place fast. So, where does the energy of the incident go? It is dissipated as heat. Thus, the loss is more.
Dielectric constant sometimes increases/decreases with frequency. It depends on the materials properties.
Under special cases, dielectric constant increases with increasing frequency.
what about if dielectric constant is independent on frequency but with a colossal behaviour? Any help?
Dear Parveen kumar,
In general, The dielectric constant is depend to many factors as the nature of sample, the thickness, the cations....
Fistly, as frequency increases, The dielectric constant (ε′) decreased rapidly. This decrease is due to the reduction of space charge polarization effect. Secondly, the increasing of the dielectric constant with an increase of the frequency may be indicate either a relaxation process, which was related to the frequency range or mean that the friction against dipole motion drops with frequency.
Kawthar Trabelsi I also Agree with your excellent answer. Thank you so much.
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