• 한국광학회지
• /
• 제13권4호
• /
• pp.356-362
• /
• 2002

비선형광학(NLO) 곁가지형 고분자계 N-(4-nitrophenul)-(L)-prolinol-poly (p-phenylene terephthalates)로 제작된 박막의 분자 배향거동을 제2 고조파발생(SHG)의 비선형광응답을 사용하여 연구하였다. 새로운 펄스 corona 배향 방법으로 NLO 발색단과 고분자 줄기를 비중심대칭 구조로 배향시켜 SHG 신호를 발생시켰다. 유리전이온도 70$^{\circ}C$를 중심으로 25$^{\circ}C$에서 80$^{\circ}C$까지 온도영역에서 반복율을 0.5 ㎑에서 10 ㎑까지 변화시키면서 인가한 펄스 고압으로 corona 배향한 결과로 곁가지 발색단과 고분자 주사슬이 스스로 재 정렬하여 형성한 구역구조를 원자간력 현미경(AFM)으로 관측하였다. 펄스 corona 전압 인가로 NLO 발색단 배향도가 증가되고, 동시에 고분자박막의 가시적손상을 획기적으로 줄이면서 SHG 신호가 증대되었으며 배향 후 이완거동도 개선되었다. 이 새로운 펄스 corona 배향 실험으로 NLO 발색단 및 고분자 주사슬이 배향과정에서 비등방으로 재배열하는 현상을 in situ로 입증할 수 있었다.

• 센서학회지
• /
• 제29권1호
• /
• pp.59-62
• /
• 2020

Currently, increasing attention is being paid to relaxor-based ferroelectric single crystals in photoacoustic images, especially for high-end applications. Among the crystals are (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-100xPT) single crystals located near their morphotropic phase boundary (x = 0.30-0.35) because of their ultrahigh piezoelectric and electromechanical coupling properties. The alternating current poling (ACP) treatment, rather than the conventional direct current poling treatment, has recently been spotlighted due to its effectiveness in enhancing the piezoelectric properties. So far, it has been suggested that the enhanced piezoelectricity originates from either a domain miniaturization to nanodomains or from an electric-field-induced monoclinic symmetry. In this study, we demonstrate by thermally stimulated depolarization current measurements that the effect of ACP is too complex to be explained using a single mechanism and that the proposed electric-field-induced monoclinic symmetry is unlikely to exist.

• 한국세라믹학회지
• /
• 제27권1호
• /
• pp.35-42
• /
• 1990

In the present investigation, ceramic PZT and Polymer were prepared. The former is Pb[(Sn1/2Sb1/2)0.1 Ti0.27Zr0.63]O3 including Pb(Sn1/2Sb1/2)O3 with good pyroelectric effect, and the latter PVA(Poly Vinyl Alcohol) with good plasticity. Then, they were fabricated to be flat by using 0-3 connectivity which is rather easily fabricated and capable of making thin film, extending surface area among the connectivities. Such were applied to the sample as variation of intensity of poling field, poling temperature, volume fraction between ceramic and polymer. Then dielectric constant, pyroelectric current, pyroelectric coefficient and the figure of merit were measured. And then their effects on pyroelectric characteristics were observed.

• 한국세라믹학회지
• /
• 제36권9호
• /
• pp.923-929
• /
• 1999

The cause of optical nonlinearity induced in thermally poled silica glass is believed to be the space charge polarization. Since the second order optical nonlinearity (electro-optic effect) can be used in optical switches the optical nonlinearity in silica glass has drawn a large attention. Space charge polarization occurs when an ionic conducting material is subjected to dc electric field by the blocking electrode. Thermal poling performed to induce the optical nonlinearity in silica glass is basically identical to the process generating space charge polarization. As a first step to understand the mechanism of space charge polarization in silica glass hence the induced optical nonlinearity the absorption currents as functions of time were measured for various types of silica glasses and analyzed by the theory of space charge polarization. It was found that the electrical relaxation exhibited a step by the space charge polarization in the relatively long time range and dielectric loss peak showed a maximum at a specific temperature which is depending on type of silica glass. It was turned out that this relaxation might be a cause of nonlinearity in electrical conductivity of silica glass.

• Journal of the Optical Society of Korea
• /
• 제12권3호
• /
• pp.205-209
• /
• 2008

We demonstrated a simple way of evaluating the duty cycle error in periodically polled lithium niobate(PPLN) based on the method of binary phase diffraction grating. To demonstrate this method, -Z face etched PPLN of desired periods were fabricated by the standard electric field poling technique. The etched PPLN was considered as a surface-relief binary phase grating. The diffraction patterns were recorded for different spatial locations along the length of the sample. The experimentally observed efficiencies of the diffracted orders were compared with the theoretically calculated values to estimate the duty cycle error.

• 한국결정성장학회지
• /
• 제16권2호
• /
• pp.53-58
• /
• 2006

조화용융조성 $LiNbO_3$ 결정에 외부 전계를 인가하였을 때 초기 도메인 생성 및 이동에 관하여 연구하였다. 0.5mm 두께의 $LiNbO_3$ 결정에 23.5, 22.0, 21.0kV/mm의 전계를 인가하였을 때 도메인 벽은 각각 28.70, 16.02, $5.75{\mu}m/sec$의 속도를 나타내었다. 분극 반전 시스템에 전류 제어를 위한 외부저항으로 $1 M{\Omega}$을 사용하였을 시 너무 빠른 도메인 성장으로 인하여 원활한 분극 반전 제어가 이루어지지 않으므로 $10 M{\Omega}$ 외부저항을 사용하여 전하량을 제어하여 50% duty cycle을 가진 주기적 분극 반전 $LiNbO_3$ 결정을 제작하였다.

• 한국재료학회지
• /
• 제12권1호
• /
• pp.75-81
• /
• 2002

The ferroelectric properties of Pb(Zr,Ti)O$_3$[PZT] films degrade when the films with Pt top electrodes are annealed in hydrogen containing environment. This is due to the reduction activity of atomic hydrogen that is generated by the catalytic activity of the Pt top electrode. At the initial stage of hydrogen annealing, oxygen vacancies are formed by the reduction activity of hydrogen mainly at the vicinity of top Pt/PZT interface, resulting in a shift of P-E (polarization-electric field) hysteresis curve toward the negative electric field direction. As the hydrogen annealing time increases, oxygen vacancies are formed inside the PZT film by the inward diffusion of hydrogen ions, as a result, the polarization degrades significantly and the degree of P-E curve shift decreases gradually. The direction and the magnitude of the remnant polarization in the PZT film affect the motion of hydrogen ions which determines the degradation of polarization characteristics and the shift in the P-E hysteresis curve of the PZT capacitor during hydrogen annealing. When the remnant polarization is formed in the PZT film by applying a pre-poling voltage prior to hydrogen annealing, the direction of the P-E curve shift induced by hydrogen annealing is opposite to the polarity of the pre-poling voltage. The hydrogen-induced degradation behavior of the PZT capacitor is also affected by the internal field that has been generated in the PZT film by the charges located at the top interface prior to hydrogen annealing.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.820-823
• /
• 2002

The asymptotic problem of a semi-infinite conducting crack parallel to the poling direction in ferroelectric ceramics subjected to electric fields is analyzed. The main mechanism for the conducting crack growth behavior is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. The shape and size of the switching zone is shown to depend strongly on the relative magnitude on the ratio of the coercive electric field to the yield electric field. It is shown that the crack growth can be either enhanced or retarded depending on the ratio of the coercive electric field to yield electric field.

• 한국광학회지
• /
• 제9권4호
• /
• pp.215-220
• /
• 1998

전기광학 폴리머(electro-optic polymer)의 다양한 전기광학 특성을 동시에 측정하기 위한 실험장치와 기법을 제안하였다. 제안된 실험장치를 이용하여 폴링(poling)전 측쇄(side-chain)결합형 전기광학 폴리머 필름에 강한 de 및 ac 전기장을 인가시 발생하는 전기광학 효과와 복굴절을 관측하였다. 다양한 폴링조건에 따른 전기광학 계수의 의존성을 실시간으로 측정하였다. 폴링후의 폴리머 필름의 열적 안정성을 평가하기 위하여 전기광학 효과의 이완현상을 측정하여 잘 알려진 전기광학 폴리머와 특성을 비교하였다. 이 실험장치는 실험과정과 시간을 줄일 수 있다.

• 한국운동역학회지
• /
• 제29권1호
• /
• pp.1-8
• /
• 2019

Objective: The purpose of this study was to confirm that the cross-country ski sprint course in PyeongChang, where the 2018 Winter Olympics course was to utilize wearable devices equipped with inertial measurement unit (IMU), global positioning system (GPS) and heart rates sensor. Method: For the data collection, two national level cross-country (XC) skiers performed classic technique on the entire sprint course. We analyzed cycle characteristics, range of motion on double poling (DP) technique, average velocity, and displacement of 3 points according to the terrain. Results: The absolute cycle time gradually decreased during starting, middle and finish sections. While the length of the DP increased and the heart rates tended to increase for men skier. In addition, the results indicated that range of motion of knee joint during starting and finish section decreased more than middle section. The errors of latitude and longitude data collected through GPS were within 3 m from 3 points. Conclusion: Through the first case study in Korea, which analyzed the location and condition of XC skiers in the entire sprint course in real time, confirmed that feedback was available in the field using various wearable sensors.