I am getting an unusual hump (or a peak maybe) near the zero crossover (time axis) in the voltage response of a bent-core liquid crystal compound using polarization reversal triangular wave method to study the spontaneous polarization. The base-line correction of the output signal/response yields an S-shaped curve with a positive as well as a negative area. Is it due to spontaneous polarization? Please help.
An oscilloscope image along with the base-line corrected plot (S-shaped) of the same is attached. In the oscilloscope image, the colour yellow corresponds to the input and the colour blue corresponds to the output signal.
Thank you.
if possible, say us, please, what is the
1) solute and the
2) electrodes ?
Dr. Samaras, Thank you for your reply.
It is basically a thermotropic bent-core liquid crystal compound filled inside a standard (Instec.) liquid crystal cell of thickness 5um. The electrodes are nothing but ITO layers coated on the glass substrates with an effective electrode area of ~ 1 cm^2.
Thank you.
It seems encouraging.
First you have to vary frequency and check the wave. Secondly vary the applied voltage and check the wave.If it is spontaneous polarization, in both the cases, the wav will increase and saturate. Pl do this and inform the result.
Keep the same input signal (yellow oscilloscope image) and if possible, replace, please, the oscilloscope input yellow signal with the i (current of circuit) signal. For your case, a potentiostat (if available in a nearby Lab.), maybe is a better alternative instrumentation to your hardware.
About measuring P(V) of liquid crystals, see, e.g., J.-P. Rivera, H. Nozary and C.Piguet, Ferroelectrics, 2002, 276, 157-170 : "Polarization loops observed in liquid crystals with a new banana-shaped ligand", Fig. 5 and some references mentioned.
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