On the Quasichemical Model of Oxygen Absorption and Ordering in a High Temperature Superconductor YBa₂Cu₃O_6+x

Abstract

In the framework of the quasichemical Williams-Bragg model an equation is obtained for the isotherm of gas absorption by the interstitials of the solvent lattice with the effect of ordering recognized; the equation is applied to analysis and interpretation of experimental data on oxygen absorption and ordering in superconducting YBa,Cu,O, + x ceramics. The oxygen absorption in both, tetragonal and orthorhombic structures is described by an absorption isotherm which fits the Langmuir equation. Extreme concentrations of the "absorption centers" are found as the oxygen absorption energy and entropy in the tetragonal (T) and orthorhomic (0) phases. The ordering of absorbed oxygen is shown to be unrelated with the "oxygen-oxygen'' pairwise interaction and is attributable to the "T --t 0" transition. The experimental isotherms of oxygen absorption by the ceramics lead to elements of the "temperature-concentration (X)" phase diagram which characterize the boundary between the T-and 0-phase regions. Im Rahmen des quasichemischen Williams-Bragg-Modells wird eine Gleichung fur die Isothermen der Gasabsorption durch Leerstellen des Losungsgitters unter Berucksichtigung des Ordnungseffekts erhalten; die Gleichung wird auf die Analyse und Interpretation von experimentellen Werten der Sauerstoffabsorption und Ordnung in supraleitenden YBa,Cu,O,+x-Keramiken angewendet. Die Sauerstoffabsorption sowohl in tetragonalen als auch rhombischen Strukturen werden durch Absorptionsisothermen beschrieben, die sich an die Langmuir-Gleichung anpassen. Extreme Konzentrationen der ,,Absorptionszentren", wie fur die Sauerstoffabsorptionsenergie und -entropie in den tetragonalen (T)und rhombischen (0)-Phasen werden gefunden. Es wird gezeigt, da13 der OrdnungsprozeR des absorbierten Sauerstoffs nicht mit der paarweisen ,,Sauerstoff-Sauerstoff '-Wechselwirkung korreliert ist und dem ,,T + 0"-Ubergang zuordnungsbar ist. Die experimentellen Isothermcn der Sauerstoffabsorption durch die Keramiken fiihren zu Elementen des ,,Temperatur-Konzentrations(X)"-Phasendiagramms, die die Grenze zwischen den T-und 0-Phasenbereichen charakterisieren.

Methodological, applied and thermodynamic aspects of hydrogen sorption by graphite and related carbon nanostructures

“…where DH = 719AE2 kJ mol 71 is the standard enthalpy of dissolution of 0.5 mol of gaseous deuterium in graphite (the mean value for the above temperature range); P D 2 and P D 2 are equilibrium and standard pressures of gaseous molecular deuterium at a specific temperature (expressed in Pa), respectively; P D 2 = 1 Pa. Making use of the results obtained elsewhere 177,179,180 we can show that the expression (1) corresponds to the approximations of the ideal gas phase (hydrogen, deuterium) and the ideal solid solution, for which the infinitely dilute solution (x 8? 0) can be taken as the standard state.…”

“…Note that in this case, it is the concentrated solution (x8/x max = 0.5) that can be chosen as the standard state for the solid phase, then DH (7)III and DS (7)III in the expression (10) are constants. 177,179 Assuming that dissolution of deuterium atoms in the graphite lattice without involvement of chemisorption centres in stage (5) does not modify the enthalpy of the system [i.e., DH (5)III & 0], the value of enthalpy determined from Eqns (4) ± ( 7) is DH (6)III & 7243 kJ mol 71 .…”

The distribution of carbon in steels

“…£ ÔÎÖÚÂÇ ÒÓÇÐÇÃÓÇÉËÏÑ ÏÂÎÑÅÑ ÄÊÂËÏÑAEÇÌÔÕÄËâ ÏÇÉAEÖ ÂÃÔÑÓÃËÓÑÄÂÐÐÞÏË ÍÂÓÃÑÂÖÔÕÇÐËÕÐÞÏË ÏÑÎÇÍÖ-ÎÂÏË g-Fe 6 C(°® g ) 6 ËØ ÕÇÓÏÑAEËÐÂÏËÚÇÔÍÖá ÂÍÕËÄÐÑÔÕß (a Cg ) Ä ÂÖÔÕÇÐËÕÇ ÏÑÉÐÑ ÑÒËÔÂÕß Ä ÓÂÏÍÂØ ÒÓËÃÎËÉÇÐËâ ËÊÑÕÇÓÏÞ ÔÑÓÃÙËË ÇÐÅÏáÓÂ ë ®ÂÍ-ËР(ÓÂÔÒÓÇAEÇÎÇ-ÐËÇ ÕËÒ ¶ÇÓÏË [19]) ÔÎÇAEÖáÜËÏ ÑÃÓÂÊÑÏ: [19].…”

“…±ÓÇAEÔÕÂÄÎâÇÕÔâ ÙÇÎÇÔÑÑÃÓÂÊÐÞÏ ÒÓËÐâÕß ÄÑ ÄÐËÏÂ-ÐËÇ ÏÈÔÔÃÂÖàÓÑÄÔÍËÇ Ë AEÓÖÅËÇ AEÂÐÐÞÇ [27,28] Ñ ÍÎÂÔÕÇÓË-ÊÂÙËË (ÓÂÔÔÎÑÇÐËË) ÂÕÑÏÑÄ ÖÅÎÇÓÑAEÂ Ä g-Fe (ÒÓË ÑÒÓÇAEÇ-ÎÈÐÐÞØ ÖÔÎÑÄËâØ), ÑÚÇÄËAEÐÑ, ÑÕÄÇÚÂáÜÇÌ ÔÖÜÇÔÕÄÇÐÐÑÌ ÑÕÓËÙÂÕÇÎßÐÑÌ àÐÇÓÅËË ËØ ÄÊÂËÏÑAEÇÌÔÕÄËâ [19], Õ.Ç. ÒÓËÕâÉÇÐËá ÏÇÉAEÖ ÍÂÓÃÑÂÖÔÕÇÐËÕÐÞÏË ÏÑÎÇÍÖÎÂÏË gFe 6 C(°® g ) 6 .…”

“…¥Îâ ÖÚÈÕ ÕÂÍÑÅÑ (ÔÓÂÄÐËÕÇÎßÐÑ ÔÎÂÃÑÅÑ) ÄÊÂË-ÏÑAEÇÌÔÕÄËâ ÏÇÉAEÖ ÂÃÔÑÓÃËÓÑÄÂÐÐÞÏË ÏÑÎÇÍÖÎÂÏË g-Fe 6 C(°® g ) 6 ÏÑÉÐÑ ËÔÒÑÎßÊÑÄÂÕß (ÍÂÍ ÒÓËÃÎËÉÇ-ÐËÇ, ËÎË ÏÑAEÇÎß) ËÊÑÕÇÓÏÖ ÔÑÓÃÙËË ¶ÂÖÎÇÓÂ ë ¤ÖÅ-ÅÇÐÅÇÌÏ [19], ÚÕÑ ÒÓËÄÑAEËÕ Í ÔÎÇAEÖáÜÇÏÖ ÄÞÓÂÉÇ-ÐËá AEÎâ ÕÇÓÏÑAEËÐÂÏËÚÇÔÍÑÌ ÂÍÕËÄÐÑÔÕË ÖÅÎÇÓÑAE (a Cg ) Ä ÂÖÔÕÇÐËÕÇ (ÒÓË n à Cg 5): £ ÔÄÇÕÇ ÄÞÛÇËÊÎÑÉÇÐÐÑÅÑ ÏÑÉÐÑ ÒÓÇAEÔÕÂÄËÕß ÖÓÂÄ-ÐÇÐËâ (ÍÓËÔÕÂÎÎÑØËÏËÚÇÔÍËÇ ×ÑÓÏÖÎÞ) ÓÇÂÍÙËÌ ÓÂÔÕÄÑ-ÓÇÐËâ CH 4 gas D C g-Fe 2H 2 gas Ë AEË××ÖÊËË C Ä g-Fe Ä ÄËAEÇ ±ÓÑÄÇAEÈÐÐÑÇ ÓÂÔÔÏÑÕÓÇÐËÇ ÒÑÍÂÊÞÄÂÇÕ, ÚÕÑ ÎÑÍÂÎßÐÑÇ ÔÑÔÕÑâÐËÇ Ë ÓÂÊÏÇÜÇÐËÇ C Ä ÂÖÔÕÇÐËÕÇ ÏÑÉÐÑ ÒÓÇAEÔÕÂÄËÕß ÍÂÍ "ËÐÕÇÓÍÂÎËÓÑÄÂÐÐÞÇ" (ÂÃÔÑÓÃËÓÑÄÂÐÐÞÇ) ÏÑÎÇÍÖÎÞ ÕËÒ g-Fe 6 C(°® g ) 6 , ÑÃÎÂAEÂáÜËÇ ÛÂÓÑÄÑÌ ÔËÏÏÇÕÓËÇÌ Ë ÔÎÂÃÑ ÄÊÂËÏÑAEÇÌÔÕÄÖáÜËÇ AEÓÖÅ Ô AEÓÖÅÑÏ (ÒÓËÕâÉÇÐËÇ, ÒÓËÄÑAEâÜÇÇ ÒÓË ÑÒÓÇAEÇÎÈÐÐÞØ ÖÔÎÑÄËâØ Í ÍÎÂÔ-ÕÇÓËÊÂÙËË). ±ÓË àÕÑÏ ÑAEËÐ ÂÕÑÏ C "ÊÂÐËÏÂÇÕ" ÛÇÔÕß ÔÕÓÖÍÕÖÓÐÑ àÍÄËÄÂÎÇÐÕÐÞØ ÑÍÕÂàAEÓËÚÇÔÍËØ ÏÇÉAEÑÖÊÎËÌ (°® g ), ÑÕÄÇÚÂáÜËØ ÑAEÐÑÏÖ "ÙÇÐÕÓÖ ÂÃÔÑÓÃÙËË" ÂÕÑÏ ÒÓËÏÇÔË (C) Ä ¤¸¬-ÓÇÛÈÕÍÇ g-Fe (ÔÏ.…”