• Title/Summary/Keyword: Hysteresis loss

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Structural and Electrical Properties of K(Ta,Nb)O3 Ceramics with Variation of Ag Contents for Electrocaloric Devices (전기열량소자용 Ag 첨가량에 따른 K(Ta,Nb)O3 세라믹스의 구조적·전기적 특성)

  • Lee, Min-Sung;Park, Byeong-Jun;Lim, Jeong-Eun;Lee, Sam-Haeng;Lee, Myung-Gyu;Park, Joo-Seok;Lee, Sung-Gap
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.6
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    • pp.442-448
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    • 2021
  • In this work, the (K1-xAgx)(Ta0.8Nb0.2)O3 (x=0.1-0.4) ceramics were fabricated using mixed-oxide method, and their structural and electrical properties were measured. All specimens represented a pseudo cubic structure with the lattice constant of 0.3989 nm. When 0.4 mol of Ag was added, second phases induced from metallic Ag and K2(Ta,Nb)6O16 phase were observed. Dielectric constant and dielectric loss of K(Ta0.8Nb0.2)O3 specimen doped with 0.3 mol of Ag were 2,737 and 0.446, respectively. The curie temperature was about -5℃, which does not change with Ag addition. The remanent polarization began to decrease sharply around 12~15℃, and the temperature at which the remanent polarization began to decrease as the applied voltage increased shifted to the high temperature side. The electrocaloric effect (ΔT) and electrocaloric efficiency (ΔT/ΔE) of the (K0.7Ag0.3)(Ta0.8Nb0.2)O3 ceramics were 0.01024℃ and 0.01825 KmV-1, respectively.

Practical Guide to the Characterization of Piezoelectric Properties (압전재료의 기초 물성 측정)

  • Kang, Woo-Seok;Lee, Geon-Ju;Jo, Wook
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.5
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    • pp.301-313
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    • 2021
  • Theoretical background for the meaning of various piezoelectric properties can be easily found in a number of textbooks and academic papers. In contrast, how they are actually measured and characterized are rarely described, though this information would be the most important especially to the researchers who just started working on the field. It follows that this report was intended to provide a practical guidance for measuring basic but essential properties of ferroelectric-based piezoelectric materials. The discussion begins with how to measurement dielectric properties such as dielectric permittivity and loss (dissipation factor), followed by piezoelectric properties such as piezoelectric constants, electromechanical coupling factor, and quality factor as well as ferroelectric features, i.e., electric field dependent polarization hysteresis. Though our discussion here is limited to the techniques that are already well-standardized, it is expected to make a seed to be developed into more challenging and creative ones.

Characteristics of the ( Pb, La ) $TiO_3$ Thin Films with Pb/La Compositions (Pb/La 조성에 따른 ( Pb, La ) $TiO_3$ 박막의 특성 변화)

  • Kang, Seong-Jun;Joung, Yang-Hee;Yoon, Yung-Sup
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.36D no.1
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    • pp.29-37
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    • 1999
  • In this study, we have prepared PLT thin films having various La concentrations by using sol-gel method and studied on the effect of La concentration on the electrical properties of PLT thin films. As the La concentration increases from 5mol% to 28mol%, the dielectric constant at 10kHz increases from 428 to 761, while the loss tangent decreases from 0.063 to 0.024. Also, the leakage current density at 150kV/cm has a tendency to decrease from 6.96${\mu}A/cm^2$ to 0.79${\mu}A/cm^2$. In the result of hysteresis loops of PLT thin films, the remanent polariation and the coercive field decrease from 9.55${\mu}C/cm^2$ to 1.10${\mu}C/cm^2$ and from 46.4kV/cm to 13.7kV/cm, respectively. With the result of the fatigue test on the PLT thin films, we have found that the fatigue properties are improved remarkably as the La concentration increases from 5 mol% to 28mol%. In particular, the PLT28) has paraelectric phase and its charge storage clensity and leakage current density at 5V are 134fC/${\mu}cm^2$ and 1.01${\mu}A/cm^2$, respectively. The remanent polarization and coercive field of the PLT(10) film are 6.96${\mu}C/cm^2$ and 40.2kV/cm, respectively. After applying of $10^9$ square pulses with ${\pm}5V$, the remanent polarilzation of the PLT(10) film decreases about 20% from the initial state. In the results, we conclude that the 10mol% and the 28mol% La doped PLT thin films are very suitable for the capacitor dielectrics of new generation of DRAM and NVFRAM respecitively.

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