Hello Everyone,
I know that the maximum ED can be calculated from dielectric displacement vs. electric field loops. But I don't have an equipment to get the loop. Composites have a non-linear behavior of dielectric displacement vs. electric field. The samples are around 10 um thick. Au are sputtered on them to make electrodes having thickness of 10 - 20 nm.
I plan to get the maximum ED from the equation: ED=0.5 C*V_bd^2. I was trying to measure C at a DC voltage near the breakdown voltage of the composites using a Hipot (VITEK models). But the hipot didn't give me a value that I can trust due to high leakage current under high DC bias (> 500 nA ).
A co-worker said I could calculate C from Tau=RC. We have a system to charge a nanocomposite capacitor, which has a high leakage current, to a voltage near the breakdown voltage. Then, the time constant is determined from a oscilloscope when capacitor discharged to a 12 MOhm resistor.
Could anyone please tell me why I could use / could not use the above measurement methods? I am asking this because I don't see any publication have done either of the above methods to report their maximum ED.
Thank you very much!
Flexible electrostatic capacitors are potentially applicable in modern electrical and electric power systems. In this study, flexible nanocomposites containing newly structured one-dimensional (1D) BaTiO3@Al2O3 nanofibers (BT@AO NFs) and the ferroelectric polymer poly(vinylidene fluoride) (PVDF) matrix were prepared and systematically studied. The 1D BT@AO NFs, where BaTiO3 nanoparticles (BT NPs) were embedded and homogeneously dispersed into the AO nanofibers, were successfully synthesized via an improved electrospinning technique. The additional AO layer, which has moderating dielectric constant, was introduced between BT NPs and PVDF matrixes. To improve the compatibility and distributional homogeneity of the nanofiller/matrix, dopamine was coated onto the nanofiller. The results show that the energy density due to high dielectric polarization is about 10.58 J cm–3 at 420 MV m–1 and the fast charge–discharge time is 0.126 μs of 3.6 vol % BT@AO-DA NFs/PVDF nanocomposite. A finite element simulation of the electric-field and electric current density distribution revealed that the novel-structured 1D BT@AO-DA NFs significantly improved the dielectric performance of the nanocomposites. The large extractable energy density and high dielectric breakdown strength suggest the potential applications of the BT@AO-DA NFs/PVDF nanocomposite films in electrostatic capacitors and embedded devices.
this may be help you dear
best reqards
Thank you very much, Dr. Nabel Kadum abd-ali. I read about energy density calculation for dielectric materials and understand that getting ED from ED=0.5CU^2 * is only valid for materials that have linear behavior of displacement versus electric field.
What is the name of the paper that you mentioned in your answer?
The method of determining the energy density (ED) by measuring the time constant (Tau = RC) and using the equation ED = 0.5 * C * V_bd^2 requires accurate measurement of the capacitance (C) and the breakdown voltage (V_bd). The method of measuring C from the time constant is appropriate for linear dielectric materials. However, for non-linear dielectric materials, such as nano-composites made of BaTiO3 and polymers, the relationship between C and voltage is non-linear and cannot be accurately represented by a single value of capacitance.
Additionally, the method of measuring C from a Hipot (VITEK models) is also limited for non-linear materials as the leakage current under high DC bias can lead to significant error in the measurement of capacitance. The high leakage current may also result in the breakdown of the sample, which would make the measurement of C and V_bd impossible.
It may be more appropriate to measure the ED of nano-composites made of BaTiO3 and polymers using the dielectric displacement vs. electric field loop, which is considered the most accurate method for determining ED in ferroelectric materials. However, if this equipment is not available, other alternative methods such as impedance spectroscopy, thermo-mechanical analysis, or piezoresponse force microscopy may be used to determine the ED of the nano-composites. These methods measure the change in the polarization of the material as a function of the applied electric field, which can provide information on the energy stored in the material.
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