Étude du système U-Sr-O par diffraction X à haute température

1999 ◽  
Vol 77 (8) ◽  
pp. 1384-1393 ◽  
Author(s):  
André Pialoux ◽  
Bernard Touzelin
Keyword(s):  
High Temperature ◽  
Lattice Parameter ◽  
Reduced Form ◽  
X Ray Diffraction ◽  
Constant Composition ◽  
X Ray ◽  
Lattice Constants ◽  
Metallic Oxides ◽  
Composition Variation ◽  
Fluorite Type

High-temperature X-ray diffraction (293 [Formula: see text] T(K) [Formula: see text] 1773) is used to investigate the reaction between strontium monoxide and uranium dioxide under controlled atmosphere (105 [Formula: see text] [Formula: see text] (Pa) [Formula: see text] 10-24), with lattice parameter measurements and composition estimates of the different uranates obtained. Thus, with a Sr/U = 1 sample, we successively observe the phases: (a) orthorhombic α-"SrUO4", whose reduction (3.67 [Formula: see text] O/U [Formula: see text] 3.62) is shown by a constant volume of the cell (V = 0.367 nm3) between 1173 et 1373 K; (b) rhombohedral β-"SrUO4", which shows a large composition variation between the metastable oxidized form (β-SrUO3.60) below 1108 K and the stable conjugate reduced form (β'-SrUO3.11) at whatever temperature; (c) "SrUO3" of constant composition (O/U [Formula: see text] 3) between 293 and 1533 K, then variable (O/U < 3) above 1533 K, with a probable second-order transformation (α-Pnma, β-Imma) for this distorted perovskite near 1073 K; (d) fluorite type U1-δSrδO2-δ solid solution for which a maximal account in SrO (δ [Formula: see text] 0.25) induces a 0.5 % thermal expansion parameter in comparison with UO2.00. A pseudo-binary "SrUO3"-"SrUO4" phase diagram is propounded. With a sample compound of Sr/U = 3, the monoclinic "Sr3UO6" perovskite is stable under [Formula: see text] [Formula: see text] 105 Pa up to 1373 K. On the other hand, in reducing atmosphere ([Formula: see text] [Formula: see text] 10-19 Pa), it becomes orthorhombic "Sr3UO5" with much greater lattice constants at every temperature.Key words: high-temperature X-ray diffraction, reactivity in metallic oxides, U-Sr-O system, nuclear fuels.

In-situ High Temperature X-ray Diffraction Study of the Am-O System

MRS Advances ◽  
2016 ◽  
Vol 1 (62) ◽  
pp. 4133-4137 ◽  
Author(s):  
E. Epifano ◽  
R. C. Belin ◽  
J-C Richaud ◽  
R. Vauchy ◽  
M. Strach ◽  
...  
Keyword(s):  
High Temperature ◽  
Lattice Parameter ◽  
Minor Actinide ◽  
Controlled Atmosphere ◽  
X Ray Diffraction ◽  
X Ray ◽  
Binary Phase Diagrams ◽  
First Time ◽  
O Phase

ABSTRACTIn the frame of minor actinide recycling, (U,Am)O2 are promising transmutation targets. To assess the thermodynamic properties of the U-Am-O system, it is essential to have a thorough knowledge of the binary phase diagrams, which is difficult due to the lack of thermodynamic data on the Am-O system. Nevertheless, an Am-O phase diagram modelling has been recently proposed by Gotcu. Here, we show a recent investigation of the Am-O system using in-situ High Temperature X-ray Diffraction under controlled atmosphere. By coupling our experimental results with the thermodynamic calculations based on the Gotcu model, we propose for the first time a relation between the lattice parameter and the departure from stoichiometry.

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.

Densification Behaviour of Nano-Size CeO2

2007 ◽  
Vol 555 ◽  
pp. 189-194 ◽  
Author(s):  
D. Djurović ◽  
Matvei Zinkevich ◽  
Snezana Bošković ◽  
V. Srot ◽  
Fritz Aldinger
Keyword(s):  
High Temperature ◽  
Redox Reaction ◽  
Lattice Parameter ◽  
Oxygen Atmosphere ◽  
X Ray Diffraction ◽  
X Ray ◽  
Densification Behaviour ◽  
Air Atmosphere ◽  
Diffraction Patterns ◽  
Lower Temperature

A nano-sized CeO2 powder was synthesized by a modified glycine nitrate process (MGNP). The synthesized powder was characterized by X-ray diffraction (XRD), the Brunauer Emmett Teller (BET) method, and transmission electron microscopy (TEM). The lattice parameter and crystallite size were determined by the Rietveld refinement of X-ray diffraction patterns. The shrinkage kinetics of the green body was continuously monitored in air and in oxygen atmospheres using a high temperature dilatometer up to 1500°C. During the high temperature sintering in air a redox reaction occurred (Ce4+ was partially reduced to Ce3+, and oxygen gas was released). The redox reaction influenced the sintering behaviour of CeO2, resulting in a decrease in density. On the basis of shrinkage kinetics data in oxygen atmosphere a master sintering curve for CeO2 was constructed. Using the concept of the master sintering curve, the densification behaviour in oxygen atmosphere was successfully predicted from early to final stages of sintering. During sintering of CeO2 at lower temperature in air atmosphere a significant contribution of the surface diffusion was observed.

Variation of cation distribution with temperature and its consequences on thermal expansion for Ca3Eu2(BO3)4

2020 ◽  
Vol 76 (4) ◽  
pp. 554-562
Author(s):  
Katarzyna M. Kosyl ◽  
Wojciech Paszkowicz ◽  
Alexey N. Shekhovtsov ◽  
Miron B. Kosmyna ◽  
Jerzy Antonowicz ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
High Resolution ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
Thermal Expansion Anisotropy ◽  
Structural Details

The structure of calcium europium orthoborate, Ca3Eu2(BO3)4, was determined using high-resolution powder X-ray diffraction data collected at the ID22 beamline (ESRF) under ambient conditions, as well as at high temperature. Rietveld refinement allowed determination of the lattice constants and structural details, including the Ca/Eu ratios at the three cationic sites and their evolution with temperature. Clear thermal expansion anisotropy was found, and slope changes of lattice-constant dependencies on temperature were observed at 923 K. Above this temperature the changes in occupation of the Ca/Eu sites occur, exhibiting a tendency towards a more uniform Eu distribution over the three Ca/Eu sites. Possible structural origins of the observed thermal expansion anisotropy are discussed.

Determination of Thermal Expansion by High-Temperature X-Ray Diffraction

1961 ◽  
Vol 5 ◽  
pp. 238-243 ◽  
Author(s):  
Dale A. Vaughan ◽  
Charles M. Schwartz
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Ceramic Materials ◽  
Lattice Parameter ◽  
Specimen Preparation ◽  
X Ray Diffraction ◽  
X Ray ◽  
And Control ◽  
Measurement And Control

AbstractTwo high-temperature X-ray diffraction cameras are described which have been employed at Battelle to determine thermal expansion of metals and ceramic materials. Specimen preparation and temperature measurement and control are described. Lattice-parameter data vs. temperature are presented for uranium, uranium dioxide, and magnesium oxide.

Investigation of tetragonal distortion in the PbTiO3–BiFeO3 system by high-temperature x-ray diffraction

1995 ◽  
Vol 10 (5) ◽  
pp. 1301-1306 ◽  
Author(s):  
V.V.S.S. Sai Sunder ◽  
A. Halliyal ◽  
A.M. Umarji
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Room Temperature ◽  
Tetragonal Distortion ◽  
X Ray Diffraction ◽  
Solution System ◽  
X Ray ◽  
Lattice Constants ◽  
Solid Solution System ◽  
Different Temperatures

Compositions in the (Pb1−xBix (Ti1−xFex)O3 solid solution system for x ⋚ 0.7 show unusually large tetragonal distortion. High-temperature x-ray diffraction was used to study the tetragonal distortion as a function of temperature (25–700 °C) for compositions (x = 0–0.7) using powders prepared by solid-state reaction in the above system. Large changes in the lattice parameters were observed over a narrow temperature range near Curie temperature (TC) for compositions near the morphotropic phase boundary (MPB) (x ≃ 0.7). Compositions near MPB showed a c/a ratio of 1.18 at room temperature. Polar plots of lattice constants at different temperatures indicated strong anisotropic thermal expansion with zero thermal expansion along the [201] direction.

Search for New Semiconductors for High Temperature Applications:The BaPb1-x BixO3 System

1998 ◽  
Vol 512 ◽  
Author(s):  
V. Ponnambalam ◽  
U. V. Varadaraju
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Single Phase ◽  
Random Distribution ◽  
Lattice Parameter ◽  
Cubic Phase ◽  
Linear Variation ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Power Factor

ABSTRACTBaPbl-xBixO3 phases with 0.6⋚ x⋚ 1.0 were synthesized by high temperature solid state reaction. Powder X-ray diffraction measurements show that all compositions are in single phase. Linear variation of lattice parameter is observed in BaPb1-xBixO3 with change in x indicating the random distribution of Pb in Bi sites. The activation energies for conduction of phases with x=0.8−0.6 obtained from ρ −T plots are same suggesting that the band gap does not change for compositions with x-0.8−0.6. The low activation energy obtained for BaBiO3 can be attributed to the structure of the compound. S versus (1000/T) data of x=1.0−0.8 exhibit a two-slope behavior. The orthorhombic to cubic phase transition could be the possible reason for the high power factor values of BaBiO3.

Analysis of the Effect of the Oxide Ion Vacancy on the Crystal Structure of La1-xCaxCrO3-δ by High-Temperature X-Ray Diffraction under Various Oxygen Partial Pressures

2005 ◽  
Vol 242-244 ◽  
pp. 9-16 ◽  
Author(s):  
Norifumi Ohba ◽  
Eri Oikawa ◽  
Takuya Hashimoto
Keyword(s):  
High Temperature ◽  
Solution Model ◽  
Ideal Solution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
Expansion Behavior ◽  
Partial Pressures ◽  
Increasing Temperature ◽  
Oxide Ion

In order to evaluate potential of La1-xCaxCrO3-δ as a material for interconnector of solid oxide fuel cells, reduction expansion was measured by using high temperature X-ray diffraction under various P(O2). Obtained reduction expansion increased with increasing temperature and Ca content. With combination of obtained lattice constants and oxygen nonstoichiometry data, the effect of oxide ion vacancy on crystal lattice and their thermodynamic behavior have been deduced. It was proposed that expansion behavior by δ of La0.9Ca0.1CrO3-δ can be explained assuming ideal solution model on oxide ion vacancies, however, deviation from ideal solution model was observed in reduction expansion behavior of La0.8Ca0.2CrO3-δ and La0.7Ca0.3CrO3-δ with δ region larger than 0.03 and 0.05, respectively. It was revealed that the crystal system approached to cubic with increase of δ in the region where the deviation from ideal solution model was observed.

A new phase of coesite SiO2

1979 ◽  
Vol 149 (3-4) ◽  
Author(s):  
A. Kirfe ◽  
G. Will ◽  
J. Arndt
Keyword(s):  
Aqueous Solution ◽  
High Pressure ◽  
High Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
Temperature Conditions ◽  
High Pressure High Temperature ◽  
New Phase

AbstractA coesite crystal synthesized from aqueous solution (Arndt and Rombach, 1976) under static high-pressure high-temperature conditions of 44 – 49 kb and 610°C was investigated by X-ray diffraction. From the lattice constants

High-temperature x-ray diffraction studies of a precursor mixture for Pb-substituted Bi-2223 superconducting wires

1998 ◽  
Vol 13 (3) ◽  
pp. 574-582 ◽  
Author(s):  
A. R. Drews ◽  
J. P. Cline ◽  
T. A. Vanderah ◽  
K. V. Salazar
Keyword(s):  
High Temperature ◽  
Rapid Heating ◽  
Phase Evolution ◽  
Lattice Parameter ◽  
Superconducting Tapes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Superconducting Wires ◽  
Silver Substrate ◽  
Xrd Patterns

High-temperature x-ray diffraction measurements of a (Bi, Pb)-2223 precursor mixture used to produce high-Jc superconducting tapes were conducted on silver and ZrO2 substrates. The precursor mixture consisted primarily of 2212, Ca2PbO4, and CuO. Phase evolution was markedly sensitive to oxygen partial pressure: In 10% O2 growth of the 2223 phase on silver was rapid, proceeded at the expense of the 2212 phase, and was preceded by the disappearance of the Ca2PbO4 phase. When slowly heated on a silver substrate in 7.5% O2 the 2212 phase melted near 800 °C and subsequently recrystallized near 820 °C in a highly textured form, but with no detectable 2223 formation. Under similar conditions on a ZrO2 substrate, the mixture exhibited no marked changes in the XRD patterns up to 850 °C. The dramatic reactivity on silver was also highly dependent on heating rate; rapid heating in 7.5% O2 to 825 °C did not result in melting of the 2212 phase or appearance of the 2223 phase. In experiments leading to formation of 2223, the c-lattice parameter of the 2212 phase contracted just prior to the onset of formation of 2223. This result is consistent with the formation of an intermediate Pb-doped phase of 2212. A transient amorphous phase appeared briefly at the onset of formation of 2223. No evidence for intergrowth conversion of 2212 to 2223 was observed.

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