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Enhanced Refrigeration Capacity and Magnetic Entropy Change in La0.55Ce0.15Sr0.3MnO3 Manganite
구본흔,M. S. ANWAR 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4
ΔSM(T), and the field dependence of the refrigeration capacity, RC, have been investigated in La0.7-xCexSr0.30MnO3 (x = 0.0 and 0.15). An enhanced RC and ΔSM(T) were observed in La0.55Ce0.15Sr0.30MnO3. Under a magnetic field change of 2 T, the maximum improvement of 20% of ΔSM(T) and 40% of RC, in comparison with La0.7Sr0.30MnO3, was observed. Moreover, Curie temperature of the La0.7Sr0.30MnO3 can tuned by adjusting the Ce concentration and makes this attractive for magnetic refrigeration at desired temperature.
Ln<sub>0.7</sub>Ca<sub>0.3</sub>MnO<sub>3</sub> (Ln=Nd, Sm, La)의 소결 거동 및 특성
전검배,구본흔,이찬규,Chon, Gom-Bai,Koo, Bon-Heun,Lee, Chan-Gyu 한국재료학회 2006 한국재료학회지 Vol.16 No.1
Effects of doping rare earth element on Ln site of $Ln_{0.7}Ca_{0.3}MnO_3$ (Ln=Nd, Sm and La) were examined from sintering behavior, structure and magnetic properties. Sintering reactions proceeded rapidly in order of $La_{0.7}Ca_{0.3}MnO_3>Nd_{0.7}Ca_{0.3}MnO_3>Sm_{0.7}Ca_{0.3}MnO_3$. This result can be explained by diffusivity of metal cation. Size of a-axis increased as following order of La<Nd<Sm, whereas c-axis was not much changed. Curie temperatures of 123K for $Nd_{0.7}Ca_{0.3}MnO_3$, 93K for $Sm_{0.7}Ca_{0.3}MnO_3$ and 225K for $La_{0.7}Ca_{0.3}MnO_3$ were obtained. This result coincides with change of Mn-O bond length causing by a-axis lattice constant.
Al3+와 Y3+ 동시치환 SnO2 투명전극 박막의 전기적 특성
김근우,구본흔,서용준,성창훈,박근영,조호제,허시내 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.10
Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. SnO2 is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of 10-3 Ω·cm and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of SnO2 were investigated. The addition of Y in SnO2 was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of SnO2. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of SnO2single-doped with Al and Y. {(x/2)Al2O3+(x/2)Y2O3}-SnO2 was used for the source of Al and Y to prevent the evaporation of Al2O3 and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of SnO2 co-doped with Al and Y will be discussed. 투명전극박막은 디스플레이 소자, 태양전지 등 광범위하게 응용되고 있는 분야이다. 그 중 SnO2는 3.5eV이상의 높은 에너지 밴드갭을 가지며, 산소 결함 때문에 본질적으로 n-형 반도체이다. SnO2는 가시광선 영역에서 90%이상의 높은 투과율을 가지며 10-3Ω·cm의 낮은 비저항을 가지는 것으로 알려져 있다. 이번 연구에서는 SnO2에 Al과 Y의 동시 치환되었을 때 특성에 미치는 영향에 대해 알아보았다. Al2O3과 Y2O3 을 SnO2에 동시 치환하여 이온반경을 주격자 이온(Sn4+)과의 이온반경비를 유사하게 조절함으로써 Strain energy를 보다 감소시켜 고용영역을 확대하고자 하였다. 결론적으로 Al과 Y의 첨가량이 4 : 2일 때 평균이온 반경이 Sn4+과 가장 유사한 것으로 확인되었으며, 이에 가장 낮은 비저항값인 6.7×10-3Ω‧㎝를 가지는 n-형 투명전극이 형성되는 것이 확인되었다.
전기저항 측정에 의한 Au-10at%Co 합금의 시효석출 현상에 관한 연구
이동환,구본흔,이찬규 國立 昌原大學校 産業技術硏究所 1995 産技硏論文集 Vol.9 No.-
The precipitation of cobalt-rich particles in Au-10at%Co alloys has been studied by electrical resistivity measurements. The kinetics of precipitation could be well described by Johnson-Mehl-Avrami equation, f(t)=1-exp(-kt??) and the values of n were found to be in the range 0.42∼0.88, 1.22∼2.38 and 0.48~0.65. The activation energy of aging Au-10at%Co alloys was determined by cross-cut method: the value varies between 51.7 and 68.4kJ/mol and is similar to the energy of motion of either a vacancy or vacuncy-solute complex through the lattice.