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Influence of CuO Addition on Dielectric Properties of (Ba,Sr)TiO_3 Thick Films
윤석우,고중혁 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.31
The structural and the dielectric properties of CuO doped (Ba,Sr)TiO_3 thick film interdigital capacitors on the alumina substrates have been investigated. Various contents of CuO dopants were added to the (Ba,Sr)TiO_3 thick films to lower the sintering temperature of the (Ba,Sr)TiO_3 thick films on alumina substrates. Thick films were screen printed on the alumina substrates; then, interdigital capacitors with five pairs of fingers with a finger gap of 50 μm, a width of 100 μm, and a length of 200 μm were fabricated with 1-μm-thick silver electrodes through an e-beam evaporation process. For the analysis of the structural and dielectric properties, X-ray diffraction and dielectric spectroscopy were employed, respectively. Scanning electron microscopy was used to determine the morphologies of the thick films. In this experiment, we found that the lattice parameters as well as the dielectric constant were decreased with increasing CuO dopants. The 3-wt% CuO-doped BST thick film have the lowest loss tangent of 0.21% at 1 MHz and the lowest leakage current density of 10 pA at 20 kV/cm.
Dielectric and Relaxation Behaviors of Screen-printed CuO-doped (Ba0.5, Sr0.5)TiO3 Thick Films
윤석우,박재영,고중혁 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41
The crystalline and the dielectric properties of screen-printed 3-wt% CuO doped (Ba0.5,Sr0.5)TiO3 thick film interdigital capacitors have been investigated. To lower the sintering temperature of the (Ba0.5, Sr0.5)TiO3 thick films on the alumina substrates, we added CuO. Twenty (20)-μm-thick films were screen printed on alumina substrates and then interdigital capacitors with five pairs of fingers with a 50-μm fingers gap were fabricated with silver electrodes through the e-beam evaporation process. From the X-ray diffraction analysis, we found that the CuO-doped (Ba0.5, Sr0.5)TiO3 thick films had a perovskite structure. Frequency dependent dielectric properties were measured in the microwave frequency range. Current versus voltage characteristics were analyzed in the elevated temperature range from 30 to 90 ℃. To understand the time-dependent current relaxation behavior, Ⅰ - T (current-time) characteristics were also measured under various applied electric fields.
윤석우 중국어문학연구회 2015 중국어문학논집 Vol.0 No.93
This article is about Du-Fu’s poetry ‘QiuYeWuShou’. This poetry is famous work Which is the description about the feeling of autumn. In other his work, Du fu often show his irrational thought, but in this work, he show relaxed and peaceful feeling in KuiZhou, He is content amid poverty and take. pleasure in acting in an honest way. In the autumn, he is Looking around in Field, feels the pleasure. and he sympathizes other people’s life. But he also yearn life office. His purposeis administrating the state to relieve the people´s suffering, and he express this motto in his work.
윤석우,이경수,남송민,고중혁,정순종,김민수 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.31
One-mol% Li<SUB>2</SUB>O excess 0.9(Na<SUB>0.52</SUB>K<SUB>0.48</SUB>)NbO<SUB>3</SUB>-0.1LiTaO<SUB>3</SUB> lead-free piezoelectric multilayer ceramic actuators were investigated to determine their aging properties. To reduce the thermal aging behavior, we applied a rectified unipolar electric field of 5 kV/mm to the specimen to accelerate the electric aging behavior. By employing a rectified unipolar electric field for the piezoelectric actuators, we could remove undesirable heating from the relaxation current in the motion of the ferroelectric domain. To accelerate the aging test, the applied electric fields had a frequency of 900 Hz. To have enough time for charging and discharging, we employed an accurate time constant to design the equivalent circuit model for the aging tester. To extract exact aging behavior, we measured the pseudo-piezoelectric coefficient before and after the aging process. We also measured the electro-mechanical coupling coefficient, the frequency-dependent dielectric permittivity, and the impedance to compare with fresh and aged specimen.
윤석우 중국어문학연구회 2015 중국어문학논집 Vol.0 No.90
秋興八首是杜甫晩年的代表名作, 以八首造成的組詩。杜甫周遊天下到夔州後, 感覺孤獨, 時節秋天, 天氣越來越凉, 憂鬱凄凉, 所以寫作秋天的感興。秋興八首的內容是如下: 在夔州的孤獨和不安感, 想長安生活, 擔心長安政治常況, 憂國衷情, 老衰的哀歡等等。强調這樣內容, 筆者選擇兩個主題。 主題是第一, 拘束感, 第二, 悲哀。拘束感是在夔州感到的憂鬱, 不安的感覺, 悲哀是杜甫感覺的感情, 杜甫的行爲是在這樣感覺下杜甫給讀者表現的行動樣態。主要心象是玉露, 江, 風, 雲, 菊花, 孤舟, 猿, 枕, 石, 藤蘿, 漁人, 燕子, 奕棋, 魚龍, 石鯨, 露冷蓮房, 漁翁等等。 結論, 杜甫抱悲哀感覺,遠望長安和長安時節的榮光, 體會長安榮光的消滅, 自己生命也消滅, 而只低頭。