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.

ZnO 의 비화학양론에 관한 연구

呂鐵鉉,崔在時 연세대학교 대학원 1975 延世論叢 Vol.12 No.2

The x-values of the nonstoichiometric chemical formula, Zn_(1+x)O, have been measured by a specially made quartz microbalance in a temperature range from 400 to 1200℃ under oxygen pressures from 1 to 1×10^-5 atom. The r-values varied between 0.00824~0.05028 and the enthalpies of formation of the nonstoichiometric compositions were 2.20 to 7.40 Kcal/mole under above conditions. The plots of log x vs. log Po₂ or log x=1/n log Po₂ show linerity and 1/n values calculated from the slopes of the plots are -1/14.0∼-1/11,1 in the temperature range of 400 to 900℃. Most of the physical properties of the zinc oxide, such as electrical conductivity, diffusion, defects and catalytic effects, can be explained through r-valves and the mechanism forming the nonstoichiometric compositions of the oxide.

혼합원자가 훼라이트 Ca_(1+x) La_(1-x) FeO_(4-y)계의 비화학양론적 조성과 그 물성에 관한 연구

여철현,편웅범,이은석,이성주 연세대학교 대학원 1989 延世論叢 Vol.25 No.1

Perovskite-related oxides of the Ca1+xLa1-xFe4-y system (0.0≤x≤0.5), possessing the K2NiF4 structure, have been prepared and studied by X-ray diffraction, Mohr salt analysis, Mo¨ssbauer effect and electrical conductivity. X-ray diffractions show that the solid solutions of this system have tetragonal or distorted tetragonal K2NiF4 structures and that the lattice volume almost constant with changing the e value. By Mohr salt analysis reveals the value of nonstoichiometric ratio y are found to be in the- wide range of 0.00~0.15. Using Mo¨ssbauer effect, the oxidation state and the magnetic hyperfine field of the iron nuclei in the samples have been studied. The value of the isomer shift is equal to that expected for trivalent and tetravalent iron ion. Electrical conductivity measurements show an decreasing the activation energy when the amount of tetravalent iron ion is increased

CdO의 NONSTOICHIOMETRIC COMPOSITIONS 에 관한 연구

여철현,최재시,김대욱 연세대학교 대학원 1975 延世論叢 Vol.12 No.2

The x-values of the nonstoichiometric chemical formula, Cd1+xO have been measured by a quartz microbalance in the temperature range of 100 to 600℃ under oxygen pressures from 1 to 10-5atm. The x-values varied 0.00051 to 0.02410 in the above conditions. The enthalpies of formation of excess cadmium in cadmium oxide, ΔHf, are 1.65 to 3.11Kcal/mole, and the positive values of ΔHf indicate that the reactions are the endothermic process. The plots of log x vs. log Po2 (or log x = 1/n log Po2) show linearity and 1/n values calculated from the slopes of the plots are -1/3.92 to - l/6.90 in the above conditions. The 1/n values are responsible for singly ionized excess cadmium at 100℃ and doubly ioni3ed excess cadmium im the temperature range of 500 to 600℃. It is considered the x-values are useful for the interpretation of the physical properties of the cadmium oxide.

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.

프라세오디뮴 산화물의 비화학량과 반도성에 관한 연구

呂鐵鉉,金旭成,洪種仁,片茂實 연세대학교 자연과학연구소 1981 學術論文集 Vol.7 No.-

The χ-values of the nonstoichiometric chemical formula, PrO_x, have been measured in a temperature range of 300 to 1200℃ under oxygen pressures of 0.2 to 10^-6 atm, and those values varied between 1.7956 and 1.5000. The enthalpies of formation of χ' in PrO_1.8003+χ', ΔH_f, are 4.00~8.36 Kcal/mole under above conditions. The plots of log χ' vs. log Po_2(or log χ'=1/n log Po_2) show linearity and 1/n values are calculated from the slopes of the plots. The electrical conductivity of the PrO_χ,σ, was also measured under similar conditions, and the σ values varied from about 10^-1 to 10^-6 ohm^-1 cm^-1 within semiconductor range. The activation energies for conduction are 0.43~0.50eV at the lower temperature region than the transition point and 0.65~0.68eV at the higher region than that under various oxygen pressures. 1/n values calculated from the plots of log σ vs. log Po_2 are -1/4.9~-1/3.4. The nonstoichiometric conduction mechanism of the oxide is discussed with χ-values, σ values and the above thermodynamic data. The χ-values of the nonstoichiometric chemical formula, PrO_x, have been measured in a temperature range of 300 to 1200℃ under oxygen pressures of 0.2 to 10^-6 atm, and those values varied between 1.7956 and 1.5000. The enthalpies of formation of χ' in PrO_1.8003+χ', ??H_f, are 4.00~8.36 Kcal/mole under above conditions. The plots of log χ' vs. log Po_2(or log χ'=1/n log Po_2) show linearity and 1/n values are calculated from the slopes of the plots. The electrical conductivity of the PrO_χ,σ, was also measured under similar conditions, and the σ values varied from about 10^-1 to 10^-6 ohm^-1 cm^-1 within semiconductor range. The activation energies for conduction are 0.43~0.50eV at the lower temperature region than the transition point and 0.65~0.68eV at the higher region than that under various oxygen pressures. 1/n values calculated from the plots of log σ vs. log Po_2 are -1/4.9~-1/3.4. The nonstoichiometric conduction mechanism of the oxide is discussed with χ-values, σ values and the above thermodynamic data.