Studies on the oxygen stoichiometry in superconducting cuprates by thermoanalytical methods

Abstract

Thermoanalytical methods provide important means for studying oxygen stoichiometries in high T c superconducting cuprates. The optimum annealing temperature for a desired oxygen content in the superconducting product or in related materials can be established by thermogravimetric measurements. By performing the final annealing in a thermobalance the amount of the incorporated or released oxygen can be conveniently both controlled and determined. Furthermore, the absolute oxygen content in the end product can be analyzed by the thermogravimetric reduction method. Finally, the stability of the oxygen content under various atmospheres can be checked utilizing either thermogravimetric or differential thermal analysis techniques. The potential and applications of thermal analysis within the above themes of cuprate superconductor research are reviewed and discussed using illustrative examples from the authors' own experimental works as well as from the literature.

Toward the rational design of non-precious transition metal oxides for oxygen electrocatalysis

“…The selection of A-site ions thus imposes constraints on B-site valence and oxygen non-stoichiometry by charge neutrality. Experimentally, the oxidation state of the transition metal ions in perovskites can be determined by X-ray absorption near-edge spectroscopy (XANES), 139, 140 X-ray photoelectron spectroscopy (XPS), 141,142 electron energy loss spectroscopy (EELS), 143 and Mössbauer spectroscopy 144 in addition to thermogravimetric analysis 145,146 and titration methods that employ redox-coupled back-titrant indicators.…”

Oxygen absorption/desorption characteristics of Pb2CuSr2RCu2O8+δ

“…The phase was discovered by Cava et al [12] in 1988 and intensively investigated in the late 1980s and early 1990s for its high-temperature superconductivity achieved through hole-doping by means of aliovalent Ca II -for-R III substitution. It was also revealed that the Pb 2 CuSr 2 (R,Ca) Cu 2 O 8 + δ system is prone to oxygen absorption up to δ ≈ 1.8 [13,14,[16][17][18][19]22]. The excess oxygen is harmful for the superconductivity, which is apparently the reason why the Pb 2 CuSr 2 (R,Ca)Cu 2 O 8 + δ system has been less thoroughly investigated for its oxygen nonstoichiometry compared to the case of e.g.…”

“…The excess oxygen is harmful for the superconductivity, which is apparently the reason why the Pb 2 CuSr 2 (R,Ca)Cu 2 O 8 + δ system has been less thoroughly investigated for its oxygen nonstoichiometry compared to the case of e.g. the protype high-T c superconductor system, CuBa 2 (R,Ca)Cu 2 O 6 + δ [22,23].…”

The YBaCo4O7+δ‐Based Functional Oxide Material Family: A Review

“…[99] By annealing under ambient-pressure oxygen it is possible to load the phase with excess oxygen up to δ ≈ 1.3, [40] but to reach the maximal oxygen content of δ = 1.5, oxygenation heat treatment under an elevated oxygen partial pressure or in a solid-medium ultra-high-pressure apparatus in the presence of an external oxygen-releasing material (KClO 3 ) is required. [100] Figure 5a shows a representative dynamic TG curve for YBaCo 4 O 7+δ recorded upon heating an oxygen-depleted (δ ≈ 0) powder in an O 2 gas flow to 500°C at a heating rate of 1°C/min and then cooling the sample back to room temperature at the same rate. Even an oxygen content of δ = 1.17, [8] which can be obtained just by heating the material in an oxygen flow at normal pressure, corresponds to an OSC value of 2000 μmol O/g, which is significantly higher than that of the commercial oxygen storage material CeO 2 -ZrO 2 (OSC = 1500 μmol O/g).…”