MgO, MnO₂첨가에 따른 Ba_(0.7)Sr_(0.3)TiO₃ceramics의 미세구조와 유전 특성 변화

임성민,홍석민,박흥진,김옥경 한양대학교 이학기술연구소 1999 이학기술연구지 Vol.1 No.-

(Ba,Sr)TiO₃ceramics에 MgO, MnO₂를 첨가하였을 때 나타나는 미세구조의 변화와 유전 특성변화를 관찰하였다. MgO 0.3 mol%부터 Mg 이온과 Ti이온의 치환이 일어나기 시작하여 0.7 mol%까지 계속 치환이 이루어지다가 그 이상에서는 더 이상의 치환이 이루어지지 않는 것을 XRD측정 결과 알 수 있었고, 치환에 으해 상전이 온도가 저온쪽으로 이동하였다. MgO는 (Ba,Sr)TiO₃의 grain 성장을 억제하는 inhibitor로 작용하고, MnO₂는 (Ba,Sr)TiO₃의 미세구조에는 거의 영향을 미치지 않는 것으로 나타났다. MgO를 첨가함에 따라 grain 의 이상성장이 억제되고 grain size의 uniformity가 증가하여 유전상수가 증가하는 경향을 나타내다가 MgO 0.7 mol% 이상에서는 grain의 성장이 너무 억제되어 유전상수가 감소하였다. MnO₂첨가에 따른 변하는, 0.03 mol%에서 유전상수가 크게 증가하고 그 이상에서는 융점이 낮은 MnO₂가 grain boundary 영역에 liquid phase로 존재하며 불순물의 역할을 하기 때문에 감소하는 경향을 나타내었다. The effects of MgO, MnO₂doping on the microstructures and dielectric properties of Ba_(0.7)Sr_(0.3)TiO₃ceramics were studied. From MgO 0.3 mol% to 0.7 mol% , replacement Ti ions by Mg ions happened, which confirmed by XRD. Decreasing of Curie temperature results from replacement of Ti ions by Mg ions. MgO acts as a inhibitor in (Ba,Sr)TiO₃and MnO₂does not affect on microstructures. We had maximum dielectric constant MgO 0.3 mol%, and dielectric constant decreased above MgO 0.70.3 mol% because grain growth reduced under 1 ㎛. MnO₂doped Ba_(0.7)Sr_(0.3)TiO₃exhibits maximum dielectric constand and minimum dielectric loss at MnO₂0.03 mol%, and dielectric loss at MnO₂0.03 mol% decreased as frequency increased.

Ba0.7Sr0.3TiO3 세라믹스의 소결온도, 성형압력에 따른 격자 뒤틀림과 유전 특성과의 관계

임성민,홍석민,박홍진,김옥경 한양대학교 이학기술연구소 2000 이학기술연구지 Vol.2 No.

소결온도와 성형압력을 각각 조절하여 Ba0.7Sr0.3TiO3 세라믹스의 결정립의 크기를 조절한 후 이에 따른 격자 뒤틀림의 변화와 유전특성과의 관계를 조사하였다. 소결온도와 성형압력이 증가함에 따라 결정립의 크기는 모두 증가하였지만 격자 뒤틀림은 소결온도가 증가함에 따라 감소하는 반면 성형압력의 증가에 대한 영향으로 증가하였지만 성형압력을 변화시킨 시편은 격자 뒤틀림의 변화와 마찬가지로 큰 변화를 나타내지 않았다. 유전변화율(dielectric tunability)은 성형압력을 변화시킨 시편이 소결온도를 변화시킨 경우보다 더 크게 나타났다. Ba0.7Sr0.3TiO3 ceramics with various grain sizes were prepared to investigate the lattice distortion dependence of dielectric properties by controlling sintering temperature and pressing. The grain sizes of the samples are increased with increasing sintering temperature and pressing pressure. The dielectric constant is increased by increasing sintering temperature due to the decrease in lattice distortion while it is not much affected by controlling pressing pressure. The sample made by controlling pressing pressure have greater dielectric tunability than those made by controlling sintering temperature.

산소 혼합비에 따른 Ba_(0.7)Sr_(0.3)TiO₃박막의 유전체 특성

홍석민,임성민,김호건,김옥경 한양대학교 이학기술연구소 1999 이학기술연구지 Vol.1 No.-

Ba과 Sr의 화학당량비를 조절하여 Ba_(0.7)Sr_(0.3)TiO₃분말 시료를 제조하여 각각 1,200℃와 1,300℃에서 calcining과 sintering을 실시한 후 3 inch 성형틀로 Ba_(0.7)Sr_(0.3)TiO₃인 sputtering target를 제작하였다. MIM구조의 capacitor를 위하여 하부전극을 Pt(1500Å)/TiN(2000Å)/SiO₂/Si로 하고, 제작한 target를 이용하여 RF sputtering방법으로 BST박막을 증착하였다. 제작한 박막의 결정구조를 X-선 회절계(XRD)로 분석한 후 Al을 상부전극으로 증착하여 축전기구조로 C-V와 I-V의 전기적 특성을 얻었다. 제작된 박막의 결정구조를 XRD 측정으로 확인한 결과 550℃ 이상의 기판온도에서 결정성장이 양호함을 보였다. 유전상수와 유전손실이 기판온도와 sputtering 가스의 산소 혼합비에 영향을 받는 것으로 확인되고 I-V를 통한 전기적 특성에서 전도기구가 Schottky 장벽에 의한 것과 높은 인가전압에서 space charge limited (SCL) 전도 특성을 보였고, 누설전류의 값은 표면구조의 영향으로 산소가스의 증가에 따라 감소하였다. Ba_(0.7)Sr_(0.3)TiO₃powders were prepared by changing stoichiometry of Pb and Ba. After they were calcined and sintered at 1200℃ and 1300℃ respectively, BST sputtering targets were made in 3 inch mould. For MIM structure capacitors, Pt(1500Å)/TiN(2000Å)/SiO₂/Si were used for bottom electrodes and the BST thin films were sputtered on bottom electrodes. After we analysed their structures by XRD, Al was evaporated on the BST films for MIM capacitor and we investiaged the electrical properties by measuring of C-V and I-V. We found that the structures of the films showed good crystalllinity above 550℃ from the results of XRD measurements. We supposed that the dielectric constant and dielectric loss of films were affected with substrate temperature and oxygen ratio of sputtering gas. In I-V behavior, we supposed that the conduction mechanism was Schottky conduction and space charge limited(SCL) conduction in high voltage range.

Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3) 단결정의 압전 특성 평가 및 응용

정호,임성민,김옥경 한양대학교 이학기술연구소 2002 이학기술연구지 Vol.4 No.-

The dielectric, piezoelectric, and elastic properties of 0.67pb(Mg_(1/3)Nb_(2/3))O_(3) - 0.33PbTiO_(3) (PMN-PT) single crystals grown by a Bridgman method was investigated. Two multiple phase transitions at ~78°C and ~145°C, from rhombohedral to tetragonal and then to cubic phase, have been observed. Even though PbMg_(1/3)Nb_(2/3))O_(3) (PMN) is relaxor materials, the phase transition of PMN-OT seems like to that of normal ferroelectric materials. The electromechanical, piezoelectric, and elastic properties of PMN-PT at rhombohedral phase are better than those of PMN-PT at teteagonal phase. The electromechanical coupling factors k_(33), k_(33)', k(_t) and piezoelectric constant d_(33) at room temperature is larger than those of commercial PZT polycry stalline ceramics. Bridgman 방법으로 성장시킨 0.67Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.33PbTiO_(3) 단결정의 유전, 압전, 탄성 특성 등을 조사하였다. 약 78°C와 145°C에서 능면체상에서 정방정상으로 다시 정방정상에서 입방정상으로 상전이가 두 번 일어나는 것이 관찰되었다. PMN은 완화형 강유전체지만 PMN-PT 단결정은 일반적인 장유전체의 상전이 특성을 나타내었다. PMN-PT 단결정은 정방정상에서 보다 능면체상에서 더 우수한 압전 특성을 나타내었다. <001> 면으로 가공된 PMN-PT 단결정의 압전 특성을 평가한 결과 전기 기계 결합 계수 k_(33),k_(33)',k_(t)등과 압전 전하 계수 d_(33)이 상온에서 상용화된 PZT 보다 더 우수한 특성을 나타내었다.

자궁경부에 발생한 악성 림프종 1 예

임채춘(Chae Chun Rhim),노성래(Sung Rae Roh),김동주(Dong Joo Kim),송민경(Min Kyung Song),이재성(Jae Sung Lee),주하경(Ha Kyong Joo),박윤희(Youn Hee Park),유기성(Ki Sung Ryu),한구택(Gu Taek Han),이종건(Jong Kun Lee),이준모(Joon Mo Lee) 대한산부인과학회 2001 Obstetrics & Gynecology Science Vol.44 No.8

The malignant lymphomas are neoplastic transformation of cells that reside predominantly in lymphoid tissues. The two major variants of malignant lymphoma are non-Hodgkin's lymphoma and Hodgkin's disease. Although both of these tumors infiltrate reticuloendothelial organs, their biologic and clinical behaviors suggest that they are probably not related. More than 90% of all cases of non-Hodgkin's lymphomas are of B-cell derivation. This observation is based upon the expression of B-lineage-restricted antigens as well as clonal rearrangements of immunoglobulin heavy and light chain genes. The malignant lymphoma localized in uterine cervix is rare and characteristically symptom-free expressed. We experienced a case of malignant lymphoma originated from uterine cervix, so we report with a brief of literature.

A Low-Voltage PLL With a Supply-Noise Compensated Feedforward Ring VCO

Sung-Geun Kim,Jinsoo Rhim,Dae-Hyun Kwon,Min-Hyeong Kim,Woo-Young Choi IEEE 2016 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 2 E Vol.63 No.6

<P>A low-voltage phase-locked-loop (PLL) circuit with a supply-noise-compensated feedforward ring voltage-controlled oscillator (FRVCO) is demonstrated. The oscillation frequency fluctuation due to supply noise is compensated by adjusting the ratio of driving strength in feedforward and direct paths in FRVCO. A prototype 400-MHz PLL circuit operating at 0.65 V is fabricated with 180-nm standard CMOS process. Measurement results show that supply-noise compensation is successfully achieved. Our PLL consumes only 242.1 mu W.</P>

Grain Size가 (Ba, Sr)TiO₃Ceramics에 미치는 영향

임성민,김옥경 漢陽大學校 自然科學硏究所 1998 自然科學論文集 Vol.17 No.-

(Ba, Sr)TiO₃ceramics의 유전적 성질은 grain size, 성분비, 그리고 제작공정에 의해 결정되는 미세구조와 깊은 연관을 갖고 있다. (Ba, Sr)TiO₃multilayer capacitors에서 capacitance를 증가시키기 위해서는 미세구조를 조절하여 유전상수를 증가시켜야 한다. 결론적으로 grain size의 적절한 조절은 (Ba, Sr)TiO₃ceramics의 유전적 성질을 향상시키는 결과를 가져온다. 그리고 향상된 유전적 성질은 multilayer capacitor에서의 크기의 축소를 가져올 수 있다. The dielectric properties of (Ba, Sr)TiO₃ceramics are associated with its microstructure, which depends on the grain size, stoichiometric ratio and ceramic processing. In order to increase the capacitance in (Ba, Sr)TiO₃multilayer capacitors, increasing the dielectric constant by careful and homogeneous developed of the microstructure is necessary. As a consequence, good control of grain size is obtained which enhances the dielectric properties of the (Ba, Sr)TiO₃ceramics. The enhanced dielectric constant allows the reduction of the layer width in multilayer capacitar.

우리나라의 Knit wear의 생산현황

민성의,박은주,신성애,안숙영,임은주,조정미,황혜숙 연세대학교 생활과학대학 1982 婦學 Vol.15 No.-

실험적 뇌지주막하출혈에 있어서 뇌기저 동맥의 미세구조의 변화에 관한 연구

민병국,김영백,황성남,석종식,최덕영,임광세 대한신경외과학회 1988 Journal of Korean neurosurgical society Vol.17 No.4

Experimental subarachnoid hemorrhage(SAH) was produced in adult cats by injection of autologous blood(6㎖) into prepontine cistern by tranclival approach and cisterna magna. The animals were sacrficed 1,3,5,7 or 14days later and basilar artery segments were prepared for electron microscopy. The following observations were made : 1) 1 to 7 days after SAH, electron micrograph showed round-shaped endothelial cells in tunica intima and disappearance of zonular occludens. Endothelial detachment from internal elastic membrane and intracytoplasmic vacuolation of endothelial cells as well as destruction of mitochondrial cirstae in tunica media. 2) 14days after SAH, electron micrograph showed the normal findings in tunica intima and tunica media of the vessel walls. On the basis of the above findings, I found that the ultrastructural changes in the basilar arterial wall, which had presumably developed as a consequence of experimental SAH were reversible.

뇌파 등전위 분포도법의 임상적 응용 : Computed Mapping of EEG

민병국,황성남,석종식,최덕영,임광세 대한신경외과학회 1987 Journal of Korean neurosurgical society Vol.16 No.1

Topographic electroencephalographic study (CME) is a newly developed method using a microcomputer system that displays the scalp topograph as the square roots of the average power spectra over each EEG frequency band on a color television screen. CME were applied to thirty patients. Fifteen patients out of them with focal neurologic deficit were analysed about CT scan and conventional EEG. The results of the study were as follows: 1) Comparing the results of CME and conventional EEG reading, CME revealed to be slightly more sensitive in detecting asymmetrical depression of background activity than the conventional reading of the EEG. 2) Topograph EEG study was more accurate than conventional EEG in lateralization of the lesion. 3) CME is very useful in topographic and objective diagnosis of functional lesion, although the source of the data is the same as that from the conventional EEG.