Pulse Power Techniques and Pulse eletroceramic capacitor

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Applications of Electroceramic Capacitor

Electric Vehicle Application

An electric vehicle (EV), also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion. An electric vehicle may be powered through a collector system by electricity from off-vehicle sources, or may be self-contained with a battery or generator to convert fuel to electricity. Because they are more environmental friendly than traditional vehicles, hence are widely accepted as a future vehicle to replace current automobile. The speed and acceleration of cars depend on the power density of the energy storage system and the maximum distance depends on energy density of the system. So the energy storage system is one of the most important component in EV and major parameter to evaluate the quality of EV.
Current commercial EV use batteries to store energy. Although battery has relatively high energy storage density, the power density is quite low, hence the speed of EV has been restricted. To enhance the performance of EV, modification of its energy storage system is necessary. Under such circumstance, researchers propose to replace battery with capacitor. Compared with battery, capacitor have several advantages: 1. Fast charging; 2. Large discharging current; 3. Long life time; 4. Large power density; 5. Environment friendly; 6. Easy to integrate in electric circuit. Moreover, recently the energy density of capacitor increase dramatically, which make capacitor possible to replace battery as energy storage system in EV.

Various Kinds of Capacitors and their Comparison

Capacitors may be divided into two main parts. One is electrochemical capacitors, which are also named as #supercapacitors or ultracapacitors$,1 have drawn much attention. These capacitors is in a form between traditional capacitors and batteries, they use electrostatic double-layer capacitance or electrochemical pseudocapacitance to store energy without any chemical reactions occur inside the capacitor, which leads to hundreds of thousands of charging-discharging cycles.2,3 As schematically illustrated in Fig. 2.1,4 the supercapacitor comprises several basic elements, including a porous separator, a pair of porous electrodes, electrolyte in the porous separator and electrodes, and a pair of current collectors. With an external bias applied between the two electrodes, the electrical charges supplied at the electrodes attract the ions with opposite charges in the electrolyte at the respective electrode interfaces. Because the porous electrodes have very high exposed surface area (up to ~103 m2/g), and thus an extremely high capacitance value, the amounts of the charge and energy stored are dramatically enhanced.5-8
For a capacitor made of a dielectric material, the electric polarization mechanisms allow more charges to be stored because the dipoles created in the dielectric material under the external bias can bind more charges on the electrodes of the capacitor.9-11 There are different types of electric polarization mechanisms, including electronic polarization, ionic polarization, dipolar orientation polarization, and space charge polarization.12 Fig. 2.2 shows that the charges in the orientated electric dipoles under external bias contribute to bind the opposite charges at the respective electrode interfaces. Because the polarization increases with the electric field, a large amount of polarization and thus the charges bound at the electrode can be realized at large voltage. For many nonlinear dielectric materials in which the polarization does not just linearly increase with the electric field, such as ferroelectrics and antiferroelectrics, the polarization and charges can be significantly enhanced with a large electric field. Because dielectric materials have a large breakdown electric field, dielectric capacitors can work at a high voltage, which can be up to several hundred volts or even higher.13-16
Figure 2.2 A schematic illustration of an electrically charged dielectric capacitor in which the charges of the orientated electric dipoles under bias contribute to bind the opposite

charges at the respective electrode interfaces

We can know from above that electrochemical capacitors and dielectric capacitors have different working principles and hence it leads to different characteristics. For better understanding the difference between these two kinds of capacitors, table 2.1 gives the detailed parameter comparison.
Pulse Power Techniques are techniques that discharge stored energy (normally hundreds or thousands of joule) in very short time (~ȝs to ms), hence allowing a very high power density (~MW). The most important issue is to investigate an energy storage system with high energy density and power density. This technique can be applied to many areas including eletron or ion acceleration, laser, nuclear fusion, electromagnetic pulse etc.
There are many ways to store the energy, for example by capacitor, inductance, machinery and chemical energy etc. Among them, dielectric capacitor has very fast discharging speed (high power density), flexibility, mature technology and low price, hence are becoming one of the most widely spreading technology for energy storage. W. N. Lawless17 et al. investigated MLCC which shows a theoretical energy density of 6 kJ/L. Moreover, After 105 times of charging and discharging cycles, the capacitor was not broken and the generated heat was also very low.

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Antiferroelectric materials and their principle for energy storage

ABO3 pervoskite oxides have many peculiar properties, such as high temperature superconductor, colossal magnetoresistance and high piezoelectric coefficients, therefore have draw much attention of material researchers. Among those materials, ferroelectric has been investigated for many years.
Ferroelectricity is a property of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. In contrast, in antiferroelectric materials, the adjacent dipoles oriented in opposite directions leading to a zero spontaneous polarization. However, the antiparallel dipoles of these compounds can be forced to be parallel by electric fields, corresponding to an electric field-induced AFE-to-ferroelectric (FE) phase transition. These significant changes at the phase transition present opportunities for potential applications such as in energy storage capacitors and displacement transducers.

Table of contents :

Chapter 1 Introduction
Chapter 2 Backgrounds and Literature Review
2.1 Application of Electroceramic Capacitor
2.1.1 Electric Vehicle Application
2.1.2 Various Kinds of Capacitors and their Comparison
2.1.3 Pulse Power Techniques and Pulse eletroceramic capacitor
2.1.4 Antiferroelectric materials and its principle for energy storage
2.1.5 Antiferroelectric films
2.1.6 Antiferroelectric films for energy storage application
2.2 PbZrO3-based antiferroelectric ceramics and films
2.2.1 Investigation of composition of PbZrO3-based antiferroelectric material
2.2.2 Effect of strain on PbZrO3-based antiferroelectric material
2.2.3 Scaling behavior of antiferroelectric material
2.3 Main purpose and content of this thesis
Chapter 3 Experiment procedures
3.1 Radio-Frequency magnetron sputtering method
3.1.1 Preparation of bottom electrode
3.1.2 Preparation of PZ film
3.2 Chemical Solution Deposition
3.2.1 Procedure of CSD method
3.3 Characterization Techniques
3.3.1 X-Ray Diffraction (XRD) Analysis
3.3.2 Scanning Electron Microscopy (SEM)
3.3.3 Atomic Force Microscopy (AFM)
3.3.4 Electrical Measurements
Chapter 4 Preparation and properties of PZNT films
4.1 Structure information of PZNT film
PbZrO3-based antiferroelectric films for energy storage applications
4.2 Dielectric properties
4.3 Polarization properties
4.4 Energy storage properties
4.5 Conclusion
Chapter 5 Preparation and energy storage properties of Pb0.97La0.02Zr(0.95Ti0.05)O3 AFEfilms
5.1 Preparation of bottom electrode
5.1.1 Introduction
5.1.2 Experiments
5.1.3 Results and discussion
5.1.4 Conclusion
5.2 Preparation of characterization of PLZT/LNO AFE films
5.2.1 Introduction
5.2.2 Experiments
5.2.3 Results and discussions
5.2.4 Conclusion
5.3 Preparation and characterization of PLZT/LSMO films
5.3.1 Introduction
5.3.2 Experiments
5.3.3 Results and discussions
5.3.4 Conclusion
5.4 Effect of top electrode on the energy density properties of films
5.4.1 Introduction
5.4.2 Experiments
5.4.3 Results and Discussions
5.4.4 Conclusion
Chapter 6 Preparation and energy storage properties of PbZrO3 films
6.1 Properties of PbZrO3 films on different substrates
6.1.1 Introduction
6.1.2 Experiments
6.1.3 Results and discussion
6.1.4 Conclusion
6.2 Effect of residual stress on energy storage property in PbZrO3 antiferroelectric thin films with different orientations
6.2.1 Introduction
6.2.2 Experiments
6.2.3 Results and discussions
6.2.4 Conclusion
6.3 Enhancement of energy storage in epitaxial PbZrO3 antiferroelectric films using strain engineering
6.3.1 Introduction
6.3.2 Experiments
6.3.3 Results and discussions
6.2.4 Conclusion
Chapter 7 Conclusions and Future works
7.1 Conclusions
7.2 Future Work
Reference

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