DearDr. Seham

Al Salam Alaikum

As I used ILs for electrodeposition of metals, I have only knowledge on their electrochemical properties. Although as I am metallurgist, and you subject is out of my knowledge, I looked at your attached file. I noticed that you expressed potenrial as (mV/cm2). Just I 'd like to tell you that potential is not a function of area and it should be expressed as (mV or V). However, current measurements should be expressed as current density (A/cm2)  

hi 

P (mc/cm2) polarization not potential 

E (Kv/cm) electric field not current density

it was written that its hysteresis loop measurements

thank you

 Dear Dr Kamal,

thank you for your answer

the DSC is the first scan heating,   I have measured the loops using sawyer -tower circuit 

the material lack center of symmetry so I doubt to be ferroelectric but the saturated hysteresis loop occurs at high temperature. so I'm not sure if it liquid crystalline ferroelectric  phase or not

To me it does not appear like a typical ferroelectric hysteresis loop.

Looks morelike a loop you would see for an electret. But I maybe wrong, one should try to confirm by other techniques for confirming the existence of ferroelectricity.

Should observe the switching currents also as suggested by Mr. Kamal Asadi.

Try the the loop measurements at different frequencies.

If it is a ferroelectric hysteresis loop, then you should be able to see a phase transition in the measured dielectric constant also.

K. Sreenivas

Dear Dr K. Sreenivas,

thank you for you answer and useful information you write.

I measure dielectric properties but in low temperature. It seems that I have to remeasure it a gain[ from low to high temperature] to investigate this transition if it ferroelectric transition or not.

But I didn't have any idea about electret.

Regards

If you can get hold of one very nice paper by a famous professor Prof. J. F. Scott

"Ferroelectrics go bananas" -  Try to google you may find the paper.

It explains clearly about the HY loops generated by electret materials.

Prof. K. Sreenivas

Dear Ms. Sesham Kamal.

I was wondering at the P-E loop you had measured 

1) It is sort of saturating at the top very strongly, as shown by the thick orange shaped line in your curves.

    Is there any limitation in the gain setting during measurement, or while drawing the P-E curves the scaling is not properly selected. 

    Why are we not able to see the data points clearly in thefigure where you are showing strong saturation.

2) Secondly the Coercive field is increasing with increasing temp. This is different when compared to normal ferroelectrics, where the Coercive field (Ec) decreases with increasing temp. to wards the phase transition.

I was a little curious to understand these differences in observations between normal soid ferroelectrics and ferroelectric liquid crystals.

Perhaps the way you characterise ferroelectric liquid crystals and the ferroelectric effect exhibited by them is different, and through different measurements.

Enclosisng one of the papers published by my collaborators which may be useful to you.

 1)  A. Choudhary et al., Journal of Applied Physics, Vol:104 (2008) page 034105

       In case you are unable to get this paper, let me know I send a PDF copy.

2) Downloaded some other useful papers for you to read, which explain how researchers have characterised FE-liquid crystals.

3) You can also consult one of my friends who is an expert on FE Liquid crystals and a very senior scientist.

Dr. Am, . Biradar at the National Physical laboratory, New Delhi, India.

His email; [email protected]

Prof. K. Sreenivas

Dear prof. Dr. K. Sreenivas,

Thank you so much for your kind help.

this behavior appear in two  different sample of the same series but with different metal halide [NH3(CH2)7NH3 CdCl4 and  NH3(CH2)7NH3MnBr4 organic inorganic hybrid

I start measuring Hys loop from room temperature up to 400-500 K at low temperature the hys is not saturated seems like ellipsoid but at high temperature seems like new phase appear the hys loop looks like an oval shape then like a square finally I get a sharp Hys loop like for ferroelectric material. I wonder and ask my professor  is there a transition to ferroelectric because the sharp saturated hys loop occurs at high temperature and these kind of material usually undergoes a structural phase change

I try to make search I found an old paper that these kind of material organo-metal halide compound may exhibit a liquid crystalline phase at high temperature

The DSC thermograph shows endothermic peak at temperature near to the saturated hys loop appears and while I measure the real part of permitivity  I get a peak at nearly the same temperature. 

I wonder if it a Phase transition to ferroelectric phase [ It strange some kind]

if it a ferroelectric liquid crystal phase 

the sample was a compresses pellet of diameter 1cm and thickness 1.5 mm coated with thin layer of silver paste

pls look to the attached file

E (KV/cm)

P( Mic C/Cm2

T (K)

Thank you

Seham

I saw the curves on Book 2.

there is no No doubt, at 328 K it looks like a typical ferroelectric hysteresis loop.

the one (in dark blue in color) really looks like a normal P-E hysteresis loop with good saturation which is seen at 325 K.

Something funny is happening at the temperatures 410 and 452 K.

Are you seeing the endothermic peaks at these temperatures (410 and 452K), or at some other temperature.

(these endothermic peaks are seen through DSC analysis)

Ferroelectric phase transitions can be studied through DSC, but just check if one observes endothermic or exothermic peaks.?

Now the coercive fields are varying and seem to vary with temp. Going up and down at different temperatures.This is little bit intriguing, and the switching process (from one state to another) is becoming sharp at higher temperatures 458 and 474 K.

Let me think and see how it can be explained.

K. Sreenivas

.

I have found that my cooperative anisotropic model of ferromagnetic hysteresis applies to electrical polarization hysteresis, and suspect that you have some rate dependence that obscures the reversals in your loops. That would include both conductivity and thermal relaxation. I have no more insight until rate is clarified.

I would suggest to repeat your dielectric measurements once again.

If possible make your temperature dependent dielectric measurements once again, but in the descending order.  I mean start at 475K and decrease the temperature down to 300K.

This is to eliminate any spurious influence of moisture on the dielectric data.

K. Sreenivas