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.

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.

CoO의 Nonstoichiometry에 관한 연구

여철현,최재시,최승락 연세대학교 대학원 1973 延世論叢 Vol.10 No.1

The Y values of the nonstoichiometric chemical formula, CoO1+Y, have been measured by a specially made quartz micro-balance in a temperature range from 0℃ to 1200℃ under oxygen pressures from 152 mmHg to 10-3 mmHg. The y values varied between 0.01850 and 0.00148 and the activation energies are usually less than 5 Kcal/mole in the above condition. The plots of log y vs log P02(or log Y= 1/n log P02) show linearity and 1/n values calculated from the slopes of the plot are 1/4.8∼1/2.7 in the temperature range of 1000℃-1200℃ under 10-3~10-1 mmHg O2 pressures. The most of physical properties of the cobaltous oxide, such as the electrical conductivity, oxidation, diffusion and catalytic effect along with the mechanism, could be explained through y values and the nonstoichiometric mechanism of the oxide.

혼합원자가 Sr_(1+x)La_(2-x)Fe_2O_(7-y) 훼라이트의 비화학양론 : 그 구조와 물리적 성질 Structure and Physical Properties

여철현,이성주,Grenier, Jean Claude 연세대학교 자연과학연구소 1985 學術論文集 Vol.14 No.-

Sr_(1+x)La_(2-x)Fe_2O_(7-y)계의 분말시료는 SrCO_3, La_2O_3및 Fe(NO_3)_3·9H_2O의 정량적 혼합물을 1350℃에서 24시간 가열하여 제조하였다. 이 분말시료를 펠�꼭�만들어 1450℃에서 24시간 동안 소결시켰다. 이 고용체의 결정구조는 x=0.0, 1.5, 1.7과 2.0인 경우는 정방정계였고, x=0.2, 0.5, 0.7, 1.0및 1.2인 경우는 사방정계였다. 각 계에 있어서 값이 증가할수록 격자체적이 감소함을 X-선 회절분석을 통하여 확인하였다. Mo¨ssbauer 스펙트라는 298K에서 측정하여 Fe^4+이온(δ=-0.24mm/sec)과 Fe^3+이온(δ=-0.23mm/sec)의 혼합원자가 상태를 확인하였다. 이 계의 Fe^4+이온과 Fe^3+이온의 혼합원자가 상태는 Mohr염 분석을 통하여 정량적으로 분석하였다. 비화학양론적 조성 y는 0.00에서 0.66사이의 값을 나타내었다. 시료의 전기전도도는 -100~140℃온도 범위에서 10^-9~1ohm^-1cm^-1의 반도체 영역에서 변하였다. 전기전도도의 활성화에너지는 0.47~0.14eV사이의 값을 나타내었다. 자기측정은 80K에서 1273K사이의 온도범위에서 실시하여 Ne´el온도는 Sr_3Fe_2O_6.90의 경우 130K 이었고, 그 값은 X값이 감소함에 따라 증가하였다. The powder samples of the Sr_(1+x)La_(2-x)Fe_2O_(7-y) system are prepared from stoichiometric mixtures of SrCO_3, La_2O_3, and Fe(NO_3)_3·9H_2O by heating at 1350℃ for 24 hours. The pellet samples are sintered at 1450℃ for 24 hours. The crystallographic structures of the solid solutions of x=0.0, 1.5, 1.7 and 2.0 are tetragonal systems and those of x=0.2, 0.5, 0.7, 1.0 and 1.2 are orthorhombic systems. In each systems, X-ray diffraction analysis reveals that the unit cell volume decreases when the x value is increased. Mo¨ssbauer spectra measured at 298K indicates that isomer shift of iron (Ⅳ) in x=2.0 is-0.24mm/sec and that of iron (Ⅲ) is 0.23 mm/sec. The mixed valency state at two kinds of Fe ion in the solid solutions is quantitatively analyzed by the Mohr salt titration method. The value of nonstoichiometric ratio y is varied from 0.00 to 0.66. Electrical conductivities of this systems are measured in a temperature range of -100 to 140℃. The conductivity values are vared from about 10^-9 to 1 ohm^-1 cm^-1 within semiconductivity range. Activation energies of electrical conductivity are varied from 0.47 to 0.14 eV. Magnetic mesurement indicates that Ne´el temerature is 130K in Sr_3Fe_2O_6.90 and increases when the x value is decreases.

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.