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백종후,이미재,최병현,지미정,임은경,남산,Paik, Jong-Hoo,Lee, Mi-Jae,Choi, Byung-Hyun,Jee, Mi-Jung,Lim, Eun-Kyeong,Nahm, Sahn 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.7
Crystal structure of $(Ba-{1-x}La_x)[Mg_\frac{1+x}{3}}Nb_\frac{{2-x}{3}}]O_3$ (BLMN) ceramics with 0\leq1x \geq was investigated using synchrotron X-ray powder diffraction (XRD) and high reso(B $a_{l-x}$L $a_{x}$)[M $g_{(1+x)}$3/N $b_{(2-x)/3}$] $O_3$lution transmission electron microscopy (HRTEM). When the La content, x, is above 0.1, the 1:2 ordered hexagonal structure found in Ba($Mg_\frac{1}{3}Nb_\frac{2}{3}})O_3$(BMN) was transformed into 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x=0.7. When x exceeded 0.7, however, BLMN was transformed into 1:1 ordered structure which has cation displacement and in-phase and anti-phase tilt of octahedra.
백종후,임은경,김창일,이미재,지미정,최병현,김세기,Paik Jong-Hoo,Lim Eun-Kyeong,Kim Chang-il,Lee Mi-Jae,Jee Mi-Jung,Choi Byung-Hyun,Kim Sei-Ki 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.3
RAINBOW(Reduced And Internally Biased Oxide Wafers) are a new class of high-displacement, piezoelectric actuator produced by selectively removing oxygen from one surface of ceramic using a high-temperature chemical reduction process. In this paper, RAINBOW actuator materials of $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_{x}Ti_{1-x})O_3$ ceramics were prepared. Its dielectric and piezoelectric properties were investigated in the vicinity of MPB. The piezoelectric properties showed the maximum value of ${\epsilon}r$ = 4871, $d_{33}$ = 610 ($10^{-12}$ m/V), $d_{31}$ = -299 ($10^{-12}$ m/V), $k_{33}$ = $71\%$, Qm = 70, in $0.4Pb(Ni_{1/3}Nb_{2/3})O_{3}-0.6Pb(Zr_{405}Ti_{595})O_3$ composition sintered at $1250^{\circ}C$. The strain - electric field characteristics of RAINBOW actuator were significantly improved comparison with the conventional bulk actuator. The prepared RAINBOW actuator showed about $390\;{\mu}m/100\;V$ displacement.
백종후,임은경,이미재,지미정,최병현,김세기,Paik, Jong-Hoo,Lim, Eun-Kyeong,Lee, Mi-Jae,Jee, Mi-Jung,Choi, Byung-Hyun,Kim, Sei-Ki 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.1
The microwave dielectric properties and their related structural characteristics in solid solutions of (1-$\chi$) Ba($Mg_{1/3}$Nb$_{2/3}$) $O_3$-$\chi$La(Mg$_{2/3}$Nb$_{1}$3) $O_3$(BLMN) have been investigated by measuring the dielectric constant($\varepsilon$r), Q value and temperature coefficient of resonant frequency($\tau$f) and by observing the crystal structure using high resolution transmission electron microscopy (HRTEM). Microwave dielectric properties showed characteristic features for specific composition. Dielectric constant($\varepsilon$$_{r}$) showed maximum value at the composition which corresponds to the phase boundary between 1 : 2 ordered and 1 : 1 ordered structure. The increase in $\varepsilon$$_{r}$ may be caused by the rattling of ions by incorporating smaller ions and the disordered structure. The variation of temperature coefficient of resonant frequency($\tau$$_{f}$) was investigated in terms of oxygen octahedra tilting.dra tilting.
Mg 결핍에 따른 Ba(Mg<sub>1/2</sub>Nb<sub>2/3</sub>)O<sub>3</sub> 세라믹스의 마이크로파 유전특성
백종후,이미재,최병현,김효태,지미정,임은경,남산,이학주,Paik, Jong-Hoo,Lee, Mi-Jae,Choi, Byung-Hyun,Kim, Hyo-Tae,Jee, Mi-Jung,Lim, Eun-Kyeong,Nahm, Sahn,Lee, Hwack-Joo 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.4
Crystal structure and microwave dielectric properties of Ba(Mg1/3Nb2/3) $O_3$ (BMN) ceramics were investigated. Ba(Mg1/3Nb2/3) $O_3$ has the 1:2 ordered hexagonal structure. The 1:2 ordering and relative density of specimens increased with small Mg deficiency(x). The variation of Q${\times}$ $f_{0}$ with Mg deficiency is very similar to that of 1:2 ordering and relative density. The highest Q${\times}$ $f_{0}$ achieved in this investigation is about 96,000 for Ba(Mg1/3Nb2/3) $O_3$. The improvement of Q${\times}$ $f_{0}$ with Mg-deficiency is related to the increase of degree of ordering and relative density of the specimen.
$La(Mg_{1/2}Ti_{1/2})O_3$ 세라믹스의 구조 및 고주파 유전 특성 연구
여재현,백종후,남산,이확주,박현민,변재동,Yeo, Jae-Hyun,Baek, Jong-Hu,Nham, Sahn,Lee, Hwack-Joo,Park, Hyun-Min,Byun, Jae-Dong 한국재료학회 1999 한국재료학회지 Vol.9 No.9
$La(Mg_{1/2}Ti_{1/2})O_3$ 세라믹스의 구조 및 고주파 유전특성에 관한 연구를 하였다. $La(Mg_{1/2}Ti_{1/2})O_3$ 는 B site 양이온이 1:1 규칙화된 단사정 구조를 가지고 있었고 격자상수는 $a = 5.5467(3) {\AA}, b = 5.5616(3) {\AA}, c = 7.8426(5) {\AA} 그리고 \beta = 89.9589 (2)^{\circ}$ 로 밝혀졌고. $P2_1/n$의 공간군을 가지고 있었다. $La(Mg_{1/2}Ti_{1/2})O_3$ 내부에는 산소팔면체의 동상 및 역상 기울림이 존재하고 $a^_a^_c^_$ 기울림 구조를 가지고 있음을 알수 있었다. 또한 A site 양이온의 역 평행이동도 발견되었다. $1600^{\circ}C$ 이상에서 소결된 시료는 모두 95% 이상의 상대이론 밀도를 가지고 있었고 유전상수는 대략 28 정도였다. $1630^{\circ}C$ 에서 5시간 소결된 시료에서 최고높은 $Q\timesf_0$값, 63,000을 얻었다. LMT의 공진주파수 온도 계수는 $>-77 ppm/^{\circ}C ~ -79 ppm/^{\circ}C$였다. The crystal structure and the microwave dielectric properties of $La(Mg_{1/2}Ti_{1/2})O_3$ ceramics have been investigated. $La(Mg_{1/2}Ti_{1/2})O_3$ has the 1:1 ordered monoclinic structure with the lattice parameters of $a = 5.5467(3){\AA}, b = 5.5616(3){\AA}, c = 7.8426(5) {\AA} and \beta = 89.9589 (2)^{\circ}$ The spacegroup of LMT is $P2_1/n$. Monoclinic LMT has the inphase and anti-phase tilting of octahedra with the $a^_a^_c^_$ tilting system. Anti-parallel shift of A-site cations was also found in LMT. The relative density of the specimens sintered above $1600^{\circ}C$ was ranged between 95 % and 96 % of the theoretical density and the dielectric constant of specimens was about 28. The highest $Q\timesf$ achieved in this investigation was 63,100 for the specimen sintered at $1630^{\circ}C$ for 5 hr. Temperature coefficient of resonance frequency ranged from $>-74 ppm/^{\circ}C ~ -79 ppm/^{\circ}C$.
Development of a Piezoelectric Ultrasonic Tooth-whitening Apparatus
이영진,백종후,이정배,최승재 한국전기전자재료학회 2013 Transactions on Electrical and Electronic Material Vol.14 No.5
The aim of this study was to develop an ultrasonic tooth-whitening apparatus using piezoelectric transducers,which enhance bleaching efficiency by applying ultrasound, while performing a teeth whitening procedure. For this purpose, an ultrasonic transducer was designed and manufactured, and the effects of reduction in the whitening material’s concentration and in the whitening treatment time through using the ultrasound cavitation phenomenon were confirmed. Also, the validity of this study was investigated by comparing the whitening performance with a commercialized optical whitener, through color comparison. The results revealed that the ultrasound whitener produced color values that were enhanced by as much as double that of the conventional LED light whitening method. Even when the operational time was reduced by half, the ultrasound method showed superior performance by over 54% compared to the conventional light whitener, revealing that the ultrasound method showed a remarkable treatment reduction effect.
Class I Flextensional 변환기의 주파수 특성 변화
강국진,백종후,이영진,Kang, Kook-Jin,Paik, Jong-Hoo,Lee, Young-Jin 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.2
We constructed a Class I flextensional transducer, and analyzed the variation of the resonance frequency of the transducer in relation to its structural and material variables. We used the FEM for the analysis. Total length of the transducer, thickness and material properties of the shell have large effects on the resonance frequency. While outer radius of the ceramic stack and material properties of the ceramic stack have no effect on the resonance frequency. In addition, the validation of the FE model was verified by manufacturing and comparison of the impedance analysis. Results of the present work can be utilized to design a Class I flextensional transducers of various resonance frequency.
회전기기 실시간 동작상태 모니터링을 위한 자가발전 기반 센서모듈
김창일,백종후,여서영,박범근,정영훈 한국센서학회 2019 센서학회지 Vol.28 No.5
Rotating devices are commonly installed in power plants and factories. This study proposes a self-powered sensor node that is powered by converting the vibration energy of a rotating device into electrical energy. The self-powered sensor consists of a piezoelectric harvester for self-power generation, a rectifier circuit to rectify the AC signal, a sensor unit for measuring the vibration frequency, and a circuit to control the light emitting diode (LED) lighting. The frequency of the vibration source was measured using a piezoelectriccantilever-type vibration frequency sensor. A green LED was illuminated when the measured frequency was within the normal range. The power generated by the piezoelectric harvester was determined, and the LED operation was assessed in terms of the vibration frequency. The piezoelectric harvester was found to generate a power of 3.061 mW or greater at a vibration acceleration of 1.2 g (1 g =9.8 m/s2 ) and vibration frequencies between 117 and 123 Hz. Notably, the power generated was 4.099 mW at 122 Hz. As such, our self-powered sensor node can be used as a module for monitoring rotating devices, because it can convert vibration energy into electrical energy when installed on rotating devices such as air compressors.
BT-BNT계에서 (Bi<sub>0.5</sub>Na<sub>0.5</sub>)TiO<sub>3</sub> 첨가에 따른 효과
이미재,백종후,김세기,김빛남,이우영,이경희,Lee, Mi-Jai,Paik, Jong-Hoo,Kim, Sei-Ki,Kim, Bit-Nam,Lee, Woo-Yong,Lee, Kyung-Hee 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.1
Lead free positive temperature coefficient of resistivity (PTCR) ceramics based on $BaTiO_3-(Bi_{0.5}Na_{0.5})TiO_3$ solid solution were prepared by a conventional solid state reaction method. The phase structure was showed single phase with perovskite structure regardless calcinations temperature and $Ba_{1-x}(Bi_{0.5}Na_{0.5})_xTiO_3$ structure was transformed from tetragonal to orthorhombic phase at $x{\geq}0.15$ mole. The XRD peaks with $45^{\circ}{\sim}46^{\circ}$ shifted in right the influence of crystal structure change and the intensity of peak was decreased with additive $(Bi_{0.5}Na_{0.5})TiO_3$. The curie temperature risen with additive $(Bi_{0.5}Na_{0.5})TiO_3$ but disappeared for $(Bi_{0.5}Na_{0.5})TiO_3$ addition more than 0.15 mole in TMA. In relative permittivity, the curie temperature by the transform of ferroelectric phase risen with additive $(Bi_{0.5}Na_{0.5})TiO_3$ but decreased in relative permittivity. Also, the peak of new curie temperature showed the sample containing $0.025{\sim}0.045$ mole of $(Bi_{0.5}Na_{0.5})TiO_3$ near $70^{\circ}C$ caused by phase transform from ferroelectric to ferroelectric and the peak of new curie temperature disappeared at 0.045 mole of $(Bi_{0.5}Na_{0.5})TiO_3$. In our study, it was found that the PTCR in $BaTiO_3-(Bi_{0.5}Na_{0.5})TiO_3$ system was possible for $0{\sim}0.025$ mole of $(Bi_{0.5}Na_{0.5})TiO_3$ and the maximum curie temperature by phase transition showed about at $145^{\circ}C$.