scholarly journals Self-Organized V - Mo Oxide Fibers by the Micro-Pulling Down Method

2009 ◽  
Vol 1223 ◽  
Author(s):  
Detlef Klimm ◽  
Krzysztof Orlinski ◽  
Dorota A. Pawlak
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Eutectic Composition ◽  
Intermediate Phase ◽  
X Ray Diffraction ◽  
Simple Modification ◽  
X Ray ◽  
On Demand ◽  
Self Organized ◽  
Experimental Parameters

ABSTRACTThe V2O5-MoO3 mixtures offer a whole range of materials where properties can be adjusted by simple modification of experimental parameters, which may be utilized for manufacturing metamaterials with on-demand properties. The V2O5-MoO3 system contains an intermediate phase V9Mo6O40, with a small fraction of V4+ instead of V5+. Consequently, this system should rather be considered as pseudobinary. The V4+ content depends on the oxygen partial pressure in the atmosphere. Thus, by changing the oxygen partial pressure one can tailor the electric properties of the system, and by changing the supercooling, the morphologic structure of crystallized bodies as well. For better understanding of this system differential thermal analysis and thermodynamic modeling was performed. Fibers of eutectic composition between V9Mo6O40 and MoO3 were grown by the micro-pulling-down technique. X-ray diffraction confirmed the existence of the V9Mo6O40 intermediate phase.

Effect of Oxygen Partial Pressure on Stability of High-Tc Phase in Sintered Bi-Pb-Sr-Ca-Cu-O Superconductos

1989 ◽  
Vol 169 ◽  
Author(s):  
H.K. Lee ◽  
K.W. Lee ◽  
D.H. Ha ◽  
J.C. Park
Keyword(s):  
Phase Transformation ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Superconducting Phase ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
High Tc Phase ◽  
Effect Of Oxygen

AbstractThe effect of oxygen partial pressure on stability of high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system has been investigated using x-ray diffraction, resistivity and a.c. susceptibility measurements. It was found that part of the high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system was transformed into the low-Tc phase (80 K) and insulating phases by heating in the temperature range 600 C to 880°C in O2 of one atmosphere. The original high-Tc phase was restored upon retreatment in a low oxygen partial pressure of 0.1 atmosphere. The reversible superconducting phase transformation is discussed in conjunction with the formation mechanism of the high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system.

High temperature X-ray diffraction studies of the decomposition mechanism of YBa2Cu3O7−δ at an oxygen partial pressure less than 10 Pa

1995 ◽  
Vol 10 (3) ◽  
pp. 165-169 ◽  
Author(s):  
W. Pitschke ◽  
W. Bieger ◽  
G. Krabbes ◽  
U. Wiesner
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Solid State Reaction ◽  
Peritectic Reaction ◽  
Decomposition Reaction ◽  
Primary Decomposition ◽  
X Ray Diffraction ◽  
X Ray

The crystallographic data of YBa2Cu3O7−δ, Y2BaCuO5, BaCu2O2, and YBa4Cu3O9 at high temperatures and p(O2)<10 Pa have been derived on the basis of HT-XRD measurements. Whereas Y2BaCuO5 expands nearly isotropically, YBa2Cu3O7−δ and BaCu2O2 show anisotropic expansions. Furthermore, the first decomposition step of the considered compounds at p(O2)<10 Pa was observed. BaCu2O2 melts congruently at T ≍ 1273 K and Y2BaCuO5 decomposes via a peritectic reaction into Y2O3, Y2BaO4 and melts at T ≍ 1323 K. A solid-state reaction into Y2BaCuO5 and BaCu2O2 was indicated for YBa2Cu3O7−δ at T ≍ 1123 K. Because YBa4Cu3O9 becomes unstable at T ≍ 1123 K, this compound cannot be formed by the primary decomposition reaction of YBa2Cu3O7−δ

In-situ analysis of chemical expansion and stability of SOFC cathodes

2014 ◽  
Vol 1655 ◽  
Author(s):  
Mirela Dragan ◽  
Scott Misture
Keyword(s):  
High Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Lattice Parameter ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Chemical Expansion ◽  
X Ray ◽  
Reducing Conditions ◽  
The Stability

ABSTRACTIn this work high-temperature X-ray diffraction has been used to investigate thermal and chemical expansion as well as overall phase stability for various cathode materials: Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF), La0.3Sr0.7CoO3 (LSC37), La0.6Sr0.4CoO3 (LSC64) and La0.6Sr0.4Fe0.8Co0.2O3 (LSCF), as a function of temperature in reducing conditions. When perovskites materials are under a low oxygen partial-pressure condition, the lattice parameter and overall dimension increase. Their chemical expansion has comparable values. From the viewpoint of the stability of these phases, the high-temperature X-ray diffraction results indicate no phase decomposition can be one of the reasons for material failure at the current experimental oxygen partial pressure. LSF is most stable, while LSC and LSCF form oxygen vacancy-ordered phases and then decompose when heated to 1000°C under atmospheres with pO2 as low as 10-5 atm.

Structure refinements of seven natural olivine crystals and the influence of the oxygen partial pressure on the cation distribution

1981 ◽  
Vol 155 (1-2) ◽  
Author(s):  
G. Nover ◽  
G. Will
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Extinction Coefficient ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Volcanic Origin ◽  
X Ray ◽  
Anisotropic Temperature ◽  
Natural Olivine ◽  
Temperature Factors

AbstractMg/Fe order in olivine has been determined by X-ray diffraction data, for example by Wenk and Raymond (1973). We have now studied the dependence of the Mg/Fe order vs. oxygen partial pressure. Two natural olivine samples of volcanic origin containing respectively 10 and 12 % fayalite were selected. The atomic positions, anisotropic temperature factors, extinction coefficient and site occupancies have been refined toThese experiments seem to indicate that the prevailing oxygen partial pressure determines the different Mg/Fe order found in natural olivine crystals.

scholarly journals Effect of Oxygen Partial Pressure on the Phase Stability of Copper–Iron Delafossites at Elevated Temperatures

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1888 ◽  
Author(s):  
Thomas Stöcker ◽  
Ralf Moos
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
High Temperatures ◽  
Phase Stability ◽  
Elevated Temperatures ◽  
Process Window ◽  
Thermoelectric Generators ◽  
X Ray Diffraction ◽  
Characterization Methods ◽  
X Ray

Oxide-based materials are promising candidates for use in high temperature thermoelectric generators. While their thermoelectric performance is inferior to commonly used thermoelectrics, oxides are environmentally friendly and cost-effective. In this study, Cu-based delafossites (CuFeO2), a material class with promising thermoelectric properties at high temperatures, were investigated. This work focuses on the phase stability of CuFeO2 with respect to the temperature and the oxygen partial pressure. For this reason, classical material characterization methods, such as scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, were combined in order to elucidate the phase composition of delafossites at 900 °C at various oxygen partial pressures. The experimentally obtained results are supported by the theoretical calculation of the Ellingham diagram of the copper–oxygen system. In addition, hot-stage X-ray diffraction and long-term annealing tests of CuFeO2 were performed in order to obtain a holistic review of the phase stability of delafossites at high temperatures and varying oxygen partial pressure. The results support the thermoelectric measurements in previous publications and provide a process window for the use of CuFeO2 in thermoelectric generators.

Growth and Characterization of PbTiO3 and Pb(Zr,Ti)O3 Thin Films by MOCVD

1994 ◽  
Vol 361 ◽  
Author(s):  
Y. Gao ◽  
W. Dong ◽  
B.A. Turtle
Keyword(s):  
Thin Films ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Depth Profiling ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Pzt Films ◽  
Uniform Composition

ABSTRACTFerroelectric PbTiO3 and Pb(Zr,Ti)O3 thin films with a perovskite structure were grown on MgO and Pt/Ti/SiO2/Si by MOCV.D. The microstructure and composition of the films were characterized by x-ray diffraction, SEM, and AES. Preferred orientation of either (111) or (100)/(001) was obtained on the Pt/Ti/SiO2/Si substrates at temperatures from 600 °C to 650 °C The preferred (111) orientation was attributed to the formation of the Pt3Ti phase in the Pt layer of the substrates, whereas the (100)/(001) orientations were inferred as the growth rate effect. AES depth profiling indicated a uniform composition through the thickness of the PZT films. However, SEM showed different topography and microstructure of the PZT films deposited in different oxygen partial pressure. Electrical properties of the PZT films appear varied as a function of the oxygen partial pressure in the reactor.

Formation of Superconducting La2−xSrxCaCu2O6−δ Ceramic with Application of O2-HIP Technique

1991 ◽  
Vol 251 ◽  
Author(s):  
Kiyoshi Oshima ◽  
Yuichi Watanabe ◽  
Masasuke Takata ◽  
Kozo Ishizaki
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Strong Correlation ◽  
Hot Isostatic Pressing ◽  
Lattice Parameters ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Isostatic Pressing ◽  
Diffraction Patterns

ABSTRACTSuperconducting La2−xSrxCaCu2O6−δ ceramics (x=0−0.6) were prepared with application of the oxygen-hot-isostatic pressing (O2-HIP) technique. The Tc of various samples was found to depend on both the Sr content and the applied oxygen partial pressure in the HIP treatment. The maximum Tc onset of 50K was observed for samples of the composition x=0.3 and 0.4 HIPped at 1050°C under 60atm oxygen partial pressure, and x=0.1 and 0.2 HIPped at 1050°C under 400atm oxygen partial pressure, respectively. From the analysis of x-ray diffraction patterns for superconducting substances, it was found that there existed a strong correlation between superconducting properties and the lattice parameters.

scholarly journals Prereduction of Nchwaning Ore in CO/CO2/H2 Gas Mixtures

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1097
Author(s):  
Trygve Schanche ◽  
Merete Tangstad
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Iron Oxides ◽  
Reduction Rate ◽  
Gas Mixtures ◽  
X Ray Diffraction ◽  
Co2 Gas ◽  
X Ray ◽  
Reduction Of Iron ◽  
Partial Pressures

Prereduction of Nchwaning manganese ore was investigated by isothermal reduction between 600 and 800 °C to optimize the conditions for industrial pretreatment of manganese ores. Experiments were conducted in CO/CO2 gas mixtures with and without hydrogen at two different oxygen partial pressures. Ore in the size fraction 9.52–15 mm was reduced in a thermogravimetric furnace, and the O/Mn ratio from the chemical analysis was used to determine the extent of prereduction. The samples were investigated by X-ray diffraction to investigate the evolution of phases under the course of reduction. The X-ray diffraction revealed that bixbyite and braunite (I and II) were reduced to manganosite with no or limited formation of hausmannite. Reduction of iron oxides subsided with wüstite, which is stabilized by manganese in the monoxide phase, and hydrogen was seen to improve the reduction of iron oxides. Modeling revealed that the reduction rate increased 2.8-fold upon increasing the CO content from 30% to 70% in a CO/CO2 gas mixture. The addition of hydrogen improved the reduction rate with factors of 1.3 and 2.6 for the low and the high oxygen partial pressures, respectively. Hence, the optimal conditions for pretreatment can be achieved by keeping the oxygen partial pressure as low as possible while adding hydrogen to the reducing gas and ensuring a high reduction temperature. Successful pretreatment limits the extent of the Boudouard reaction in the submerged arc furnace, reducing the amount of CO produced and, thus, reducing the CO available for pretreatment. Hydrogen is a useful addition to the pretreatment unit since it lowers the oxygen partial pressure and improves the kinetics of prereduction.

Effect of Oxygen Partial Pressure on Properties of ZnO Films Deposited on Freestanding Diamond Films

2013 ◽  
Vol 544 ◽  
pp. 230-233
Author(s):  
Ke Tang ◽  
Lin Jun Wang ◽  
Jian Huang ◽  
Bing Ren ◽  
Jie Zhou ◽  
...  
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Diamond Films ◽  
Flux Ratio ◽  
Zno Films ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
X Ray ◽  
Effect Of Oxygen ◽  
Ar Gas

Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of freestanding diamond (FSD) films by the direct current (DC) magnetron sputtering method in an oxygen (O2) + argon (Ar) gas mixture. The effect of oxygen partial pressure on properties of ZnO films was investigated by X-ray diffraction (XRD). The results showed that when flux ratio of argon to oxygen was 1, the ZnO films had a better crystalline quality.

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