• Title/Summary/Keyword: Ferroelectric Cathode

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Effect of Asymmetric Electrode Structure on Electron Emission of the Pb(Zr0.8Ti0.2)O3 Ferroelectric Cathode (Pb(Zr0.8Ti0.2)O3강유전 음극에서 비대칭 전극구조가 전자 방출 특성에 미치는 영향)

  • 박지훈;김용태;윤기현;김태희;박경봉
    • Journal of the Korean Ceramic Society
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    • v.39 no.1
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    • pp.92-98
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    • 2002
  • To investigate the electrode structural effect on the ferroelectric electron emission, the electric field distribution in a 2-dimensional structure was calculated as a function of upper electrode diameter, and the switching charge density and emission charge were measured simultaneously. The simulation of the electric field distribution showed that an asymmetric electrode structure could cause a stray field on the bare surface of the ferroelectric cathode near the edge of upper electrode. The distance of stray field from the electrode edge increased with increasing ferroelectric thickness, but it did not depend on the upper electrode diameter. The switching charge density increased more on the cathode with smaller upper electrode diameter. This was attributed to the stray field on the bare ferroelectric surface near the electrode edge, because the stray field for the asymmetric ferroelectric cathode enhanced polarization switching near the electrode edge. From the switching charge density, the distance of stray field from the electrode edge was calculated as about 11-14${\mu}{\textrm}{m}$. The threshold voltage of electron emission was 61-68 kV/cm, which was almost 3 times lager than the coercive voltage. The threshold voltage was not determined just by coercive voltage, but by strength and distance of the stray-field, which largely depended on the geometrical structure of ferroelectric cathode.

Effect of Electrode Structures on Electron Emission of the $Pb(Zr_{0.56}Ti_{0.44})O_3$ Ferroelectric Cathode ($Pb(Zr_{0.56}Ti_{0.44})O_3$ 강유전체 음극의 전극 모형에 따른 전자 방출 특성)

  • Seo, Min-Su;Hong, Ki-Min
    • Journal of the Korea Institute of Military Science and Technology
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    • v.13 no.4
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    • pp.699-707
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    • 2010
  • Electric-field-induced electron emission from the three kinds of $Pb(Zr_{0.56}Ti_{0.44})O_3$ ferroelectric cathodes with different electrode structure has been investigated. Regardless of the electrode structures, a threshold field of the each cathode was 2.5-2.6kV/mm, which is 3 times higher than the coercive field of $Pb(Zr_{0.56}Ti_{0.44})O_3$ material. Although the waveform of the electron currents was affected by the structure of the electrode, no significant difference for the emission properties such as the peak current and the pulse width was observed from the three kinds of the cathodes. However, the current density of the cathode was dependent on the electrode structure. From the simulation of electric field distribution, the surface flashover, and the injury region of the cathode surface, it was proved that the prime electrons were initiated at the electrode-ceramic-vacuum triple point by field emission and the emission currents were strongly enhanced by the surface plasma.

Electron Emission from $Pb(Zr_xTi_{1-x})O_3$ Ferroelectrics by Pulsed Electric Field (펄스 전기장에 의한 $Pb(Zr_xTi_{1-x})O_3$ 강유전체의 전자 방출)

  • 김용태;윤기현;김태희;박경봉;곽상희
    • Journal of the Korean Ceramic Society
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    • v.37 no.1
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    • pp.6-11
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    • 2000
  • Electron emission from the Pb(ZrxTi1-x)O3 ferroelectrics by pulsed electric field has been investigated as a function of Zr/Ti ratios such as 35/65, 50/50 and 65/35 below 250kV/cm. Electrons were emitted regardless of the applied field polarity to the rear electrode. When the negative field was applied to the rear electrode, the electron emission charge was more stable. It was proved that the electrons were emitted at the edge of the upper electrode. The emission charge increased in order of 65/35>50/50>35/65. The electron emission characteristics were dependent on the ferroelectric properties such as polarization and coercive field. The emission charge and emission threshold field were affected by the polarization change and the coercive field, respectively. This result explains that the electron emission is a field emission with polarization induced surface potential by a modified Fowler-Nordheim plot of emission charge.

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Influense of the high-voltage conductivity on peculiarity of polarization ferroelectric polymer on based vinylidenefluoride

  • Kochervinskii, V.V.;Chubunova, E.V.;Lebedinskii, Y.Y.;Pavlov, A.S.;Pakuro, N.I.
    • Advances in materials Research
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    • v.4 no.2
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    • pp.113-132
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    • 2015
  • The phenomena of high-voltage polarization and conductivity in oriented vinylidenefluoride and tetrafluoroethylene copolymer films have been investigated. It was shown that under certain electric fields, injection of carriers from the material of electrodes appears The barrier for holes injection in the copolymer was found to be lower than that for electrons. It results in more effective screening of the external field near the anode than near cathode. Electrones, ejected from cathode, creating negative charge by trapping on the surface. It is shown that the electrons injected from cathodes create a negative homocharge on the copolymer surface and then become captured on the surface shallow traps. Their nature has been studied by the x-ray photoelectron spectroscopy. It was shown that these traps may consist of chemical defects in the form of new functional groups formed by reactions of surface macromolecules with sputtered atoms of aluminum. The asymmetric shape of hysteresis curves was explained by the difference in mobility of injected holes and electrons. These factors caused appearance of "non-closed" hysteresis curves for fluorine-containing polymer ferroelectrics. Hysteresis phenomena observed at low electric fields (below coercive ones) are to associate with the behavior of the domains localized in the ordered regions formed during secondary crystallization of copolymers.