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비선형광학 단결정 KTP 의 상전이 및 완화특성에 관한 연구
최병춘 ( Byung Chun Choi ) 한국센서학회 1998 센서학회지 Vol.7 No.6
We have carried out the measurements of complex dielectric constants with impedance/gain-phase analyzer using capacitor method and the experiments of high temperature X-ray powder diffraction with X-ray diffractometer using θ -2θ scan method for the KTP single crystal which has the premium nonlinear optical properties. From the results of high temperature X-ray powder diffraction experiments, we have found that KTP does not undergo structural phase transition below 900℃. It is clear that KTP undergoes structural phase transition around 900℃ and belongs to orthorhombic above 900℃ still. However, we have applied phenomenological relation of dielectric relaxation to the results of complex dielectric measurement and have found that relaxation mechanism of KTP well satisfies the Cole-Cole relation over the temperature range from -78℃ to 200℃. And also the relaxation time well satisfies the Vogel-Fulcher relation. It is regarded that the hopping and thermally activated diffusion mechanism may control the conduction behavior of KTP above 200℃.
이혜연(Hea Yeon Lee),최병춘(Byung Chun Choi),정중현(Jung Hyun Jeong) 한국센서학회 1999 센서학회지 Vol.8 No.2
PbTe thin films of high quality were deposited on HF-treated Si(100) substrates at various substrate temperature by pulsed laser deposition technique. XRD patterns showed that PbTe layers were well-crystallized to a cubic phase with (h00) preferred orientation with tine substrate temperature up to 300℃. PbTe films could not form at substrate temperature above 400℃ because of reevaporation of the Pb. According to AFM image, the surface of films was composed of small granular crystals and flat matrix. According to the increase of substrate temperature, the grain size at film surface becomes larger. By Hall-effect measurement, the carrier concentration and Hall mobility of n-type PbTe films grown by T_(sub)=300 ℃ were 3.68 x l0^(18)cm^(-3) and 148 ㎠/Vs, respectively.
Dielectric Properties of Li_1-xNa_xNbO₃ Mixed Crystal
Kim, Jeong-Bae,Choi, Byung-Chun,Lee, kwang-Sei,Kim, Jae-Hyung 인제대학교 1991 仁濟論叢 Vol.7 No.1
Li1-xNaxNbO3(x=0.3)혼정의 온도에 따른 유전적 성질을 1kHz에서 10MHz 주파수 영역에 걸쳐 조사하였다. 25~1100℃ 온도 영역에서 측정된 유전상수 실수부의 비정상적 거동이 관측되었으며, 이것은 상전이와 연관된 것으로서, 483℃이상에서는 상유전상, 310℃ -483℃ 사이에서는 반강유전상, 310℃이하에서는 강유전상으로 판단된다. 유전상수의 하수부가 500℃이상에서 증가하는 것은 이온전도에 의한 효과로 설명된다.