Srx La₁_x Fe₃_y계의 결정학적 구조와 비화학양론에 관한 연구

여철현,편무실,강삼룡 明知大學校 産業技術硏究所 1984 産業技術硏究所論文集 Vol.3 No.-

The solid solutions of the ?? systems with χ=1.00, 0.75 and 0.50 are prepared from stoichiometric mixtures of carbonate (SrCO₃), nitrate (Fe (NO₃)₃·9H₂O) and oxide (La₂O₃) by heating at 1300℃ for three days. Crystallographic structures of the solutions are all simple cubic systems and the lattice parameters of the cubic unit cells are enlarged with the introduction of lantanium according to their X-ray diffraction analysis. The mixed valence state of two kinds of Fe ion in the ferrite systems is analyzed by the Mohr salt titration method. It is possible to produce the nonstoichiometric compounds such as ?? by the appropriate heating treatment of the solutions under atmospheric air or oxygen pressure for a long time. The crystallographic structure and the nonstoichiometric compositions of the ?? systems are discussed with relation to their physical properties.

방사선에 의한 결정의 결함구조에 관한 연구

片茂實,呂鐵鉉 명지대학교 1983 明大論文集 Vol.14 No.-

Single crystal of pottassium, Hydrogen, sulfate(KHSO_4) have been grown from the saturated solution by the evaporation method at the optimum conditions. Radiation damages in the single crystal caused by r-irradiation of 11.25×10^6 Rentgen have given rise to several paramagnetic centers. Electron spin resonance (ESR) spectra of the crystals are obtained with the X-bond EPR spectrometer at room temperature. The ESR Reaks of the paramagnetic species are found to be anisotropic but an isatlopic peak of Gaussian shape at g=2.0036 is assigned to SO_3 -radical. The g-values of all the species at various angles between the other oxis besides the rotating axes and the magenetic field are obtained from the distances between anisotropic peaks of the species and the isotropic peak of SO_3 -radical. The principal g-values of the trapped radicals are calculated from the plots of g^2 vs θ. All the species are identibud with the corresponding principal g-values and the defect structure of the KHSO_4 crystal is also discussed in terms of the species.

Study of the Nonstoichiometry and Physical Properties of the$Nd_{1-x}Sr_xFeO_{3-y}$ System

Chul Hyun Yo,Hyung Rak Kim,Kwang Hyun Ryu,Kwon Sun Roh,Jin Ho Choy Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.8

The nonstoichiometric perovskite solid solutions of the $Nd_{1-x}Sr_xFeO_{3-y}$ system for the compositions of x=0.00, 0.25, 0.50, 0.75, and 1.00 have been prepared at $1150^{\circ}C$ in the air pressure. The compound of x=0.00, NdFe$O_{3.0}$, contains only $Fe^{3+}$ ion in octahedral site and the others involves the mixed valence state between $Fe^{3+}$ and $Fe^{4+}$ ions. The mole ratio of $Fe^{4+}$ ion or the ${\tau}$-value increases steadily with the x-value and then is maximized at the compositionof x= 1.00. The nonstoichiometric chemical formulas of the system are formulated from the x, ${\tau}$ and y values. From the Mossbauer spectroscopy, the isomer shift of $Fe^{3+}$ ion decreases with the increasing x-value, which is induced by the electron transfer between the$Fe^{3+}$ and $Fe^{4+}$ ions. The transfer is made possible by the indirect interaction between $Fe^{3+}$ and$Fe^{4+}$ ions via the oxygen ion. The eg electrons of the$Fe^{3+}$ ions are delocalized over all the Fe ions. Due to the electron transfer, the activation energy of electrical conductivity is decrease with the increasing amount of $Fe^{4+}$ ion.

Nonstoichiometry of the Terbium Oxide

Yo Chul Hyun,Ryu Kwang Sun,Lee, Eun Seok,Kim Keu Hong Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.1

The x values of nonstoichiometric chemical formula, $Tb_4O_{7-{\delta}}\;or\;TbO_{1.5+x}$, have been determined in temperature range from 600$^{\circ}$C to 1000$^{\circ}$C under oxygen partial pressure of 2 ${\times}$ 10$^{-1}$ to 1 ${\times}$ 10$^{-5}$ atm by using quartz microbalance. The x values varied from 0.0478 to 0.1964 in the above conditions. The enthalpy of formation for x' in TbO$_{1.5+(0.25-xo-x')}$, ${\delta}H_f$, was 4.93-3.40 kcal mol$^{-1}$ and the oxygen partial pressure dependence was -1/8.80∼-1/11.8 under these conditions. The electrical conductivity of the $TbO_{1.5+x}$ was measured under the same conditions and the values varied from about 10$^{-3}$ to 10$^{-6}\;{\Omega}^{-1}cm^{-1}$ within semiconductor range. The activation energies for the conduction increase with oxygen partial pressure from 0.83 to 0.89 eV under the above conditions. The l/n values obtained from the oxygen pressure dependence of the conductivity are 1/4.4-1/5.2. The conduction mechanism, defect structure, and other physical properties of the oxides are dicussed with the x values, the electrical conductivity values, and the thermodynamic data.

Structural Ordering Effect on Photoluminescence Properties of $Eu^{3+}$ Doped Perovskite Tungstate $A_2BWO_6$ System

Yo, Chul-Hyun Korean Society of Photoscience 1998 Journal of Photosciences Vol.5 No.4

The optical spectroscopic properties of the ordered perovskite structure A2BWO6 doped with Eu3+ have been studied. The experimental result about Eu3+ ordering in the system of A2BWO6 indicate the different structural conditions. Some influence of Eu3+ substitutioin on the different types of cation site have been investigated.

산화네오디뮴의 비화학량과 반도성에 관한 연구

呂鐵鉉,金旭成,鄭元陽,片茂實 연세대학교 자연과학연구소 1980 學術論文集 Vol.5 No.-

NdO_(1.5+x)로 표시되는 비화학양론적 조성식의 x값을 측정한 결과, 200℃~1200℃ 온도범위와 10^-6~0.2기압 산소압력 범위에서 7.49×10^-6~1.06×10^-2이었다. 같은 실험조건에서 산소과잉의 생성엔탈피, ΔH_f,는 2.72~20.32 Kcal/mole 범위에서 변하였다. Log x를 Log Po_2에 대하여 (또는 Log x=1/n Log Po_2) 도시하면 직선관계가 성립하며 그 직선의 기울기로 부터 1/n값을 계산하였다. Nd_2O_3의 전기전도도(σ)를 유사한 조건에서 측정한 결과, 3.98×10^-7~6.31×10^-4 ohm^-1cm^-1이었다. A형 Nd_2O_3의 전도성 활성화에너지는 0.61~0.99eV이고, C형 Nd_2O_3의 활성화에너지는 0.11~0.33eV이었다. 전기전도도의 산소압력의 존성에서 얻은 1/n값은 1/4.6~1/6.2이었다. x값, σ값과 열역학적인 데이타를 사용하여 Nd_2O_3의 전도성 메카니즘, 결함구조 및 기타 물성등을 고찰하였다. The x-values of the nonstoichiometric chemical formula, Nd_2O_(1.5+x) have been measured in a temperature range of 200 to 1200℃ under oxygen pressures of 0.2 to 10^-6atm and the values varied between 7.49×10^-6 and 1.06×10^-2. The enthalpies of formation of excess oxygen in neodymium sesquioxide, ΔH_f, are 2.72~20.32Kcal/mole under above experinental conditions. The plots of log x vs. log Po_2 (or, log x=1/n log Po_2)show linearity, and 1/n values are calculated from the slopes of the plots. The electrical conductivity of the neodymium sesquioxide, σ, have also been measured under similar conditions, and the σ values varied between 3.98×10^-7 and 6.31×10^-4ohm^-1cm^-1. The activation energies of A-form and C-form of the oxide are 0.61~0.99eV and 0.11~0.33eV, respectively. The 1/n values obtained from the oxygen pressure dependences of the conductivity are 1/4.6~1/6.2. The conduction mechanism, defect structure and other physical properties of the oxide are discussed with x-values, σ values and the above thermodynamic data.

방사선에 의한 결정의 결함구조에 관한 연구

呂鐵鉉,鄭元陽,片茂實,崔在時 연세대학교 자연과학연구소 1979 學術論文集 Vol.3 No.-

황산수소칼슘(KHSO_4) 포화용액으로부터 증발법으로 KHSO_4 단결정을 최적조건에서 생성시킨다. 11.25×10^6 렌트겐의 방사선(r-선)조사로 생긴 단결정의 방사선손상은 몇개의 상자성 중심을 형성한다. 그 결정들의 전자스핀공명 스펙트라를 상온에서 X-띠 전자스핀공명 분석기로 얻는다. 상자성종들의 전자스핀공명(ESR) 피-크들은 무등방성을 보이지만 g=2.003인 Gauss형 등방성 피-크가 생기는 것은 SO_3^-기 때문이다. 회전축 이외 제삼의 축과 자장간에 이루는 여러 각도에서 모든 상자성종들의 g-값들은 그종들의 무등방성 피-크들과 SO_3^-기의 등방성 피-크간의 거리로부터 구할 수 있다. 결정내에 성성된 기들의 주 g-값은 g^2을 Θ에 대하여 도시한 곡선으로부터 계산하였다. 모든 상자성종들은 대응되는 특성 주-값들로부터 확인되고 결정의 결함구조는 또한 이들 종으로 고찰된다. Single crystals of Potassium Hydrogen Sulfate(KHSO_4) have been grown from the saturated solution by the evaporation method at the optimum conditions. Radiation damages in the single crystal caused by r-irradiation of 11.25×10^6 Rentgen have given rise to several paramagnetic centers. Electron spin resonance(ESR) spectra of the crystals are obtained with the X-band EPR spectrometer at room temperature. The ESR peaks of the paramagnetic species are found to be anisotropic but an isotropic peak of Gaussian shape at g=2.0036 is assigned to SO_3 radical. The g-values of all the species at various angles between the other axis besides the rotating axes and the magnetic field are obtained from the distances between anisotropic peaks of the species and the isotropic peak of SO_3^- radical. The principal g-values of the trapped radicals are calculated from the plots of g^2 vs.Θ. All the species are identified with the corresponding principal g-values and the defect structure of the KHSO_4 crystal is also discussed in terms of the species.

산화이트륨 및 산화홀뮴의 비화학양론

장순호,여철현,최재시,편무실,Chang, Soon-Ho,Yo, Chul-Hyun,Choi, Jae-Shi,Pyun, Mu-Sil 대한화학회 1984 대한화학회지 Vol.28 No.4

$YO_{1.5+x}$와 $HoO_{1.5+x}$로 표시되는 산화이트륨과 산화홀뮴의 비화학양론적 조성식의 x-값을 700$^{\circ}$C에서 1000$^{\circ}$C까지의 온도영역과 대기압에서 $1{\times}10^{-6}$기압 산소압력까지의 구간에서 중량 분석법에 의하여 측정하였다. 측정된 x-값은 온도가 상승하면 증가하고 산소압력이 증가하면 또한 증가하였다. 비화학양론적 조성의 생성엔탈피 $({\Delta}H_f)$는 산소압력이 감소하면 감소하였고 그 값이 양의 값을 갖는 것으로 과잉산소의 형성 과정이 흡열과정임을 알 수 있다. 산소압력 의존성 1/n-값은 온도가 상승하면 상승하고 양의 값을 갖는 것으로 높은 온도일수록 산소압력 의존성이 커짐을 보여 주었다. 그리고 x-값과 열역학적 자료로 부터 비화학양론적 결합과 전도성메카니즘을 규명하였다. The x-values in the nonstoichiometric chemical formulas $YO_{1.5+x}\;and\;HoO_{1.5+x}$, have been measured in the temperature range from 700$^{\circ}$C to 1000$^{\circ}$C under oxygen pressures from $2{\times}l0^{-1}\;to\;1{\times}10^{-6}$ atm by gravimetric method. The observed x-values increase with increasing temperature and oxygen pressure. The enthalpies of formation of excess oxygen in yttrium oxide and holmium oxide decrease with decreasing oxygen pressure and are all positive values representing an endothermic process. The 1/n values calculated from the slopes of the plots of log x vs. log $P_{O2}$ increase with temperature and are positive values which means the higher oxygen pressure dependence at higher temperature. We have examined the nonstoichiometric defect and conduction mechanism from x-values and thermodynamic data.

산화유로퓸의 비화학양론적 조성과 전기전도성에 관한 연구

呂鐵鉉,高錫勤,元輝俊,片茂實 연세대학교 자연과학연구소 1982 學術論文集 Vol.9 No.-

EuOx로 표시되는 비화학양론적 조성식의 χ값은 대기압하에서 측정한 결과 100∼1200℃ 온도범위에서 1.0618∼1.6938이었다. 한편 EuO_1.5000+χ´의 생성엔탈피, ??H_f는 4.39㎉/mole이었다. EuOx의 전기전도도(σ)는 650∼1,100℃ 온도범위와 2×10^-1∼1-^-6atm 산소압력 범위에서 약 10^-1∼10^(-4)ohm^(-1)㎝^(-1)으로 반도성을 나타내었다. 그러나 650℃ 이하의 온도범위에서는 전기전도도 값은 불규칙성을 나타내었다. 전기전도도의 활성화에너지는 위의 실험조건에서 약 1.16∼1.22eV 범위에서 산소압력이 증가됨에 따라 커진다. 한편 전기전도도의 산소압력 의존성을 나타내는 1/n 값도 logσ를 logPo_2에 대하여 도시한 기울기에서 계산한 결과 1/5.4∼1/5.0로 700℃에서 1,100℃로 온도가 상승함에 따라 증가함을 알 수 있다. 이상의 χ값과 σ값 및 열역학적인 데이타를 사용하여 EuOx의 비화학양론적 전도성 메카니즘을 고찰하였다. The χ values of the nonstoichiometric chemical formula, EuOx, have been measured in a temperature range of 100 to 1200℃ under atmospheric pressure. The χ valuestvaried between 1.0618 and 1.6938. The enthalpy of formation of χ´ in EuO_1.5000+χ´ or ??H_f is 4.39㎉/mole under above conditions. The electical conductivities of EuO_χ(or σ) have been measured in a temperature range of 650 to 1,100℃ under oxygen pressures of 1^-6 to 2×10^-1 atm, and the σ values varied from about 10^-7 to 10^-4ohm^-1㎝^-1 within semiconductor range. However, the conductivities of the oxide below 600℃ show irregularity. The activation energies for the conduction increase with oxygen pressure from 1.16 to 1.22eV under the above conditions. The oxygen pressure dependence of the conductivity (1/n values calculated from the slopes of plots log σ vs log Po_2) increase from 1/5.4 at 700℃ to 1/5.0 at 1100℃. The nonstoichiometric conduction mechanism of the oxide is discussed with χ values, σ values and the thermodynamic data.

Cobalt Thin Film의 Oxidation에 관한 연구

여철현,최재시,유희영,최찬유 연세대학교 대학원 1974 延世論叢 Vol.11 No.1

The kinetics of oxidation of the thin cobalt films have been studied using quartz micro-balance from 600 to 900 ℃ under various oxygen pressures. The oxidation followed the parabolic rate law in all cases and the parabolic rate constants, varied approximately from 1.64×10-12 to 1.11×10-11((g/cm2) 2 sec-1). The activation energies calculated from the plot of log kp vs. 1000/T varied between 0.08ev and 0.3ev in the above conditions. The 1/n values abtained from the plots of log kp vs. log Po2 (or log kp = 1/n log Po2)are about 1/5 to □ The mechanism for the oxidation of the cobalt film is discussed in accordance with other mechanisms such as nonstoichiometric mechanism, diffusion mechanism and conduction mechanism etc.