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Relaxation Characteristic of the Disordered Lead Scandium Niobate
김연중 한국진공학회 2015 Applied Science and Convergence Technology Vol.24 No.3
The correlation between admittance and dielectric spectroscopy of dielectric relaxation in lead scandium noibate, have been investigated. Lead scandium niobate, with composition PbSc0.5Nb0.5O3, was prepared by conventional solid state synthesis. Conductance Y’(G), susceptance Y”(B) and capacitance C of lead scandium niobate as a function of frequency and temperature were measured. From the temperature-dependence of RLC circuit, insight into physical significance of the dielectric properties of lead scandium niobate is obtained. The relative strong frequency dependent of dielectric properties in lead scandium niobate is observed, and the phase transition occurred at a broad temperature region. Also, the value of critical exponent γ=1.6 showed on heating process. The long relaxation times part enlarged diffuse by conductivity effects with increasing temperature, and the ordering between Sc3+ and Nb5+ in PSN influences complex admittance and dielectric properties. Confirmed the typical characteristic of lead-type relaxor in the Raman spectra of lead scandium niobate and major ranges are between 400 and 900 cm-1.
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.