• Title/Summary/Keyword: ZnO piezoelectric

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Power Enhancement of ZnO-Based Piezoelectric Nanogenerators Via Native Defects Control

  • Kim, Dohwan;Kim, Sang-Woo
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.297.2-297.2
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    • 2013
  • Scavenging electricity from wasteful energy resources is currently an important issue and piezoelectric nanogenerators (NGs) based on zinc oxide (ZnO) are promising energy harvesters that can be adapted to various portable, wearable, self-powered electronic devices. Although ZnO has several advantages for NGs, the piezoelectric semiconductor material ZnO generate an intrinsic piezoelectric potential of a few volts as a result of its mechanical deformation. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. Oxygen vacancies (Vo) that work as donors exist in ZnO thin film and usually screen some parts of the piezoelectric potential. Consequently, the ZnO NGs' piezoelectric power cannot reach to its theoretical value, and thus decreasing the effect from Vo is essential. In the present study, c-axis oriented insulator-like sputtered ZnO thin films were grown in various temperatures to fabricate an optimized nanogenerator (NGs). The purity and crystalinity of ZnO were investigated with photoluminescence (PL). Moreover, by introducing a p-type polymer usually used in organic solar cell, it was discussed how piezoelectric passivation effect works in ZnO thin films having different types of defects. Prepared ZnO thin films have both Zn vacancies (accepter like) and oxygen vacancies (donor like). It generates output voltage 20 time lager than n-type dominant semiconducting ZnO thin film without p-type polymer conjugating. The enhancement is due to the internal accepter like point defects, zinc vacancies (VZn). When the more VZn concentration increases, the more chances to prevent piezoelectric potential screening effects are occurred, consequently, the output voltage is enhanced. Moreover, by passivating remained effective oxygen vacancies by p-type polymers, we demonstrated further power enhancement.

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The Characterization of Interfaces between ZnO Thin Films and Metal Electrodes (ZnO 박막과 금속전극과의 계면특성조사)

  • 박성순;임원택;이창효
    • Journal of the Korean Vacuum Society
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    • v.7 no.3
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    • pp.201-207
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    • 1998
  • We have investigated about interface characteristics between ZnO thin films and metal electrodes when ZnO and metal electrodes were fabricated as piezoelectric vibrators. At this, ZnO thin films were deposited by rf reactive magnetron sputtering method. After fabricating piezoelectric vibrator of Cr/ZnO/Cr structure with optimum condition, we analyse interface characteristics between ZnO thin films and metal electrodes by I-V measurement. AES depth profile, SEM and C-V measurement. From these measurements we found that ZnO piezoelectric vibrators showed good property when they fabricated as Cr/$SiO_2$/ZnO/Cr structure. And we could confirm these things by driving, and measuring vibration displacement of piezoelectric vibrator with $SiO_2$diffusion barrier.

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Enhanced Performance of PVDF Piezoelectric Speaker Using PVDF/ZnO Nanopillar Composites (PVDF/ZnO Nanopillar 복합재료를 이용한 압전필름 스피커의 성능향상)

  • Kwak, Jun-Hyuk;Hur, Shin
    • Journal of Sensor Science and Technology
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    • v.25 no.6
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    • pp.447-452
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    • 2016
  • In this study, we fabricated and evaluated the performance of film speaker using PVDF/ZnO NP composite structure. PVDF piezoelectric films were fabricated and characterized by XRD and SEM. ZnO nanopillars were prepared by hydrothermal synthesis on prepared PVDF piezoelectric films. We analyzed and tested the acoustic signal characteristics of the piezoelectric film. In order to fabricate an acoustic structure with a wide frequency range from low to high frequency, we have fabricated various types of film speakers and investigated the frequency characteristics. As a result, the fundamental piezoelectric properties of PVDF show that the piezoelectric constant due to ZnO NP increases. And the overall acoustic signal level is also increased by 10% or more. We investigated frequency generation from 500 Hz to 10 KHz using different sizes with PVDF/ZnO NP composite film speaker.

A Study on Preferred Orientation of ZnO Piezoelectric Thin Film Using Helped Seed Layer (보조씨드층을 이용한 ZnO 압전박막의 우선배향성에 관한 연구)

  • Park, In-Chul;Kim, Hong-Bae
    • Journal of the Korean Vacuum Society
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    • v.15 no.6
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    • pp.619-623
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    • 2006
  • The most important factor which determines resonance characteristics of FBAR(Film Bulk Acoustic Resonator) is the piezoelectricity of piezoelectric film. The piezoelectric properties of ZnO thin films which is strong as FBAR piezoelectric film is determined by the degree of c-axis preferred orientation with (002) plan. Therefore, many researchers have been interested in the study on the preferred orientation of the piezoelectric thin film. This paper has studied the preferred orientation of ZnO piezoelectric thin films using the helped seed layer of ZnO. The result shows that the c-axis ZnO thin films with columnar grains that the value of standard $deviation(\sigma)$ of XRD rocking curve is of $\sigma=1.15^{\circ}$ have the excellent piezoelectric property.

Dielectric and Piezoelectric Characteristics of Low Temperature Sintering 0.20Pb(Zn1/3Nb2/3)O3-0.80Pb(Zr0.48Ti0.52)O3 Ceramics with the Addition of Sintering Aid ZnO (소결조제 ZnO 첨가에 따른 저온소결 0.20Pb(Zn1/3Nb2/3)O3-0.80Pb(Zr0.48Ti0.52)O3 세라믹스의 유전 및 압전특성)

  • Yoo, Ju-Hyun;Lee, Yu-Hyong;Kim, Do-Hyung;Lee, Il-Ha;Kwon, Jun-Sik;Paik, Dong-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.2
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    • pp.126-130
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    • 2008
  • In this study, in order to develop low loss multilayer piezoelectric actuator, PZN-PZT ceramics were fabricated using $Li_2CO_3,\;Bi_2O_3$, CuO and ZnO as sintering aids, their structural, piezoelectric and dielectric characteristics were investigated according to the amount of ZnO addition, At the sintering temperature of $870^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of 0.4 wt% ZnO added specimen (sintered at $870^{\circ}C$) showed the optimum value of $7.812g/cm^3$, 0.535, 916, 1399, 335 pC/N respectively. Taking into consideration above piezoelectric properties of the specimen sintered at low temperature, it was concluded that PZN-PZT ceramics using 0.4 wt% ZnO as additive showed the optimum characteristics as the composition ceramics for low loss multilayer piezoelectric actuator application.

A Study on the Characteristics of Dielectric and Piezoelectric in (Na,K)$NbO_3$-system Pb-free Piezoelectric Ceramics add ZnO (ZnO를 첨가한 (Na,K)$NbO_3$계 무연 압전 세라믹스의 유전 및 압전 특성에 관한 연구)

  • Ryu, Sung-Lim;Kim, Si-Chul;Lee, Kyung-Sun;Lee, Chung-Ho;Yoo, Ju-Hyun;Kim, Young-Min
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.11a
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    • pp.218-219
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    • 2005
  • In this paper, in order to develop Pb-free piezoelectric ceramics, $[Li_{0.04}(Na_{0.44}K_{0.52})-(Nb_{0.86}Ta_{0.10}Sb_{0.04})]O_3$ ceramic was fabricated with the variation of ZnO addition. Piezoelectric properties of the ceramic were varied with the amount of ZnO addition and showed the maximum kp value at 0.2 wt% ZnO addition. Qm of ZnO added ceramics showed lower values than the non-added ceramics, however, the kp was increased by the addition of ZnO up to 0.2 wt%. At the sintering temperature of 1110$^{\circ}C$ and the calcination temperature of 850$^{\circ}C$, the optimal values of density=473g/$cm^3$, kp=0.473, $\varepsilon_r$=1403 were obtained.

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Piezoelectric Properties in ZnO Dopped (Na,K)NbO3 Ceramics (ZnO가 첨가된 (Na,K)NbO3계 세라믹스의 압전 특성)

  • Ryu Sung-Lim;Kweon Soon-Yong;Ur Soon-Chul;Kim Si-Chul;Yoo Ju-Hyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.8
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    • pp.707-711
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    • 2006
  • ZnO was doped up to 0.3 wt% for improving the electrical properties of lead-free $[Li_{0.04}(Na_{0.44}Ko_{0.52})-(Nb_{0.86}\;Ta_{0.10}\;Sb_{0.04})]O_3$ piezoelectric ceramics. The ceramics were fabricated with the conventional sintering processes. Crystal structure of the samples was tetragonal phase regardless of ZnO amount. However, the piezoelectric properties were varied with the ZnO amount. The electro-mechanical coupling factor $(k_p)$ was with the ZnO amount up to 0.2 wt% but decreased with the further addition. the maximum value of $k_p$ was 0.475. Density, piezoelectric charge constant and relative dielectric constant was also showed maximum value at 0.2 wt%. The maximum values are $4.75g/cm^3$, 275 pC/N, 1403, respectively. In contrast, the mechanical quality factor $(Q_m)$ was not varied with increasing the ZnO addition up to 0.2 wt% but rapidly increased at 0.3 wt%.

Nanogenerator Device Based on Piezoelectric Active Layer of ZnO-Nanowires/PVDF Composite (ZnO-나노와이어/PVDF 복합체를 압전 활성층으로 한 나노발전기 소자)

  • Lim, Young-Taek;Shin, Paik-Kyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.11
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    • pp.740-745
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    • 2014
  • ZnO nanowires were grown by hydrothermal synthesis process and piezoelectric poly vinylidene fluoride (PVDF) was then coated on top of the ZnO-nanowires by spray-coating technique. The composite layer of ZnO-nanowires/PVDF was applied to an energy harvesting device based on piezoelectric-conversion mechanism. A defined mechanical force was given to the nanogenerator device to evaluate their electric power generation characteristics, where output current density and voltage were examined. Electric power generation property of the ZnO-nanowires/PVDF based nanogenerator device was compared to that of the nanogenerator device with ZnO-nanowires as single active layer. Effect of the ZnO-nanowires on improvement of power generation was discussed to examine its feasibility for the nanogenerator device.

Piezoelectric Properties of 0.98(Na0.5K0.5)NbO3-0.02Li(Sb0.17Ta0.83)O3+0.01wt%ZnO Ceramics with a Sintering Temperature (소결 온도에 따른 0.98(Na0.5K0.5)NbO3-0.02Li(Sb0.17Ta0.83)O3+0.01wt%ZnO 세라믹스의 압전 특성)

  • Lee, Dong-Hyun;Lee, Seung-Hwan;Lee, Sung-Gap;Lee, Ku-Tak;Lee, Young-Hie
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.7
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    • pp.543-546
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    • 2011
  • We studied sintering temperature to enhance the piezoelectric properties of $0.98(Na_{0.5}K_{0.5})NbO_3-0.02Li(Sb_{0.17}Ta_{0.83})O_3$+0.01wt%ZnO (hereafter NKN-LST+ZnO) lead free piezoelectric ceramics. The synthesis and sintering method were the conventional solid state reaction method and sintering was executed at $1,080\sim1,120^{\circ}C$. We found that NKN-LST+ZnO ceramics at optimal sintering temperature showed the improved piezoelectric properties at the optimal sintering temperature. The NKN-LST+ZnO ceramics show good performance with piezoelectric constant $d_{33}$= 153 pC/N sintered at $1,090^{\circ}C$. The results reveal that NKN-LST+ZnO ceramics are promising candidate materials for lead-free piezoelectric application.