Oxygen non-stoichiometry in Y2BaCuO5

• Published in: Journal of materials science letters Vol. 10; no. 15; pp. 872 - 874
• Main Authors: JANSA, L, HRNCIR, K, SKACEL, V, JANDA, M, HORAK, J
• Format: Journal Article
• Language: English
• Published: Dordrecht Kluwer Academic Publishers 1991
• Subjects: Applied sciences; Exact sciences and technology; Metal powders; Metals. Metallurgy; Powder metallurgy. Composite materials; Production techniques; Superconducting materials; Heat treatment; Electrical conductivity; Metal powder; Oxygen pressure; Yttrium Barium Copper Alloys; Non stoichiometric composition; Oxide ceramics
• ISSN: 0261-8028; 1573-4811
• DOI: 10.1007/BF00724766

The oxygen non-stoichiometry of the orthorhombic compound Y2BaCuO5 was investigated by measuring the dependence of the electrical conductivity on the oxygen partial pressures and qualitatively interpreting the results. A plot of log conductivity (sigma) versus 1/T showed a plateau in the range 460-570 K, which is probably related to the desorption of O2 molecules from the surface of the sample. This desorption is accompanied by a decrease in hole concentration. The log sigma-log pO2 dependence showed a minimum at 793 K and oxygen pressure of about 0.066 atm. This minimum was interpreted in terms of the existence of two types of point defects. For pO2 greater than 0.066 atm., incorporation of O2 atoms into the sites of O2 vacancies increases the holes concentration. In the region of electron conduction, i.e. for pO2 less than 0.066 atm., the slope of the dependence approaches the value -1/6. The increase in conductivity in the region of electron conduction is probably due to the formation of O2 vacancies at lower pressures and higher temperatures. The results show that Y2BaCuO5 ceramic may be suitable as a substrate for YBa2Cu3O7-x films. 5 refs.