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김연중 한국진공학회 2015 Applied Science and Convergence Technology Vol.24 No.6
Ferroelectric Pb2(Sc,Nb)O6 were prepared under two different sintering conditions using the oxide mixing method and the electrical properties were measured. The sintering conditions were 1350oC for 25 minutes and 1400oC for 20 minutes. EDX spectroscopy and XRD were used to determine the crystalline characteristic of the Pb2(Sc,Nb)O6 compositions Pyrochlore phase showed about 2% in all Pb2(Sc,Nb)O6 specimens. It expands the growth of crystals in samples sintered at 1400oC than 1350oC, but all samples were the optimal crystallization. The temperature and frequency dependence of the complex dielectric constant and admittance were measured to analyze the electrical properties. The high dielectric constant of the specimens reflects the good stoichiometry and crystallization. The maximum value of the dielectric constant in the two specimens treated with sintering at 1350oC and 1400oC were more than 27,000, and the dielectric loss at room temperature is smaller than 0.05. The maximum dielectric constant decreased with increasing frequency, the transition temperature also increased in Pb2(Sc,Nb)O6 compositions. The admittance and susceptance values reach a peak at all temperatures, and the magnitude of the peak increases with increasing measuring temperature. Strong frequency dependent of maximum admittance, susceptance, dielectric constant and dielectric loss were observed.
원발성 후복막강 기형종과 교차성 융합 이소신을 동반한 터너씨 증후군 1예
김연중 대한영상의학회 1988 대한영상의학회지 Vol.24 No.1
In 1938, Turner described a clinical entity in phenotype females characterized by sexual infantilism con-genital webbed neck and cubitus valgus. After then the occurrence of renal anomalies in patients with Turner's syndrome has been recognized. Associated crosses fuses renal ectopia is very rare. Primary retroperitoneal teratoma is also rare and usually during childhood. The authors report a case of primary retroperitoneal teratoma and crossed fused renal ectopia with Tumer's syndrome(mosaic type). The clinical pathological and radiographical findings are reviewed.
Changes in Physical Properties of Ta5+-doped BaTiO3 Solid Solution
김연중 한국진공학회 2018 Applied Science and Convergence Technology Vol.27 No.6
Structural properties for the substitution of Ta5 + ions in the BaTiO3 crystal lattice were observed by SEM/EDS. The formation of perovskite phase and the change of (111), (200) and (002) planes of BaTiO3 solid solution containing a small amount of Ta5+ were studied. As a result, the relationship between the dielectric properties and the polycrystalline structure of Ta5+-doped BaTiO3 was confirmed. It was found that the maximum dielectric constant of the Ta5+-doped BaTiO3 solid solution was more than about 8000, and the transition temperature shifted slightly toward the lower temperature as compared with the pure BaTiO3. The dielectric constants of all the samples measured in the temperature region above the transition temperature showed some diffusivity and satisfied the modified Curie-Weiss law.
Characterization and Physical Properties of Ba0.9Sb0.1TiO3 Solid Solution
김연중 한국진공학회 2019 Applied Science and Convergence Technology Vol.28 No.2
BaTiO3 is known to be an environmentally friendly electronic material with a phase transition temperature that can be controlled through the substitution of an appropriate additive. Physical changes of grain growth in Ba0.9Sb0.1TiO3 were analyzed by adding a small amount of antimony to pure BaTiO3. The Ba0.9Sb0.1TiO3 solid solution with antimony substitution was prepared under various calcination and sintering conditions. The optimal conditions for sintering were confirmed and the grain growth process was clearly understood. As a result, the relationship between the dielectric properties and the polycrystalline structure of Ba0.9Sb0.1TiO3 substituted with antimony was confirmed. The maximum dielectric constant of the Ba0.9Sb0.1TiO3 solid solution was found to exceed about 5500 and the dielectric constant at room temperature reached nearly 4000. The transition temperature of Ba0.9Sb0.1TiO3 was shifted closer to room temperature than that of pure BaTiO3. Unlike the phase transition behavior of pure BaTiO3, the dielectric constant curve, which is a function of temperature for all samples, showed a very gradual change.