%0 Journal Article
%T XPS Study of Mechanically Activated YBa2Cu3O6+汛 and NdBa2Cu3O6+汛
%A A. V. Fetisov
%A G. A. Kozhina
%A S. Kh. Estemirova
%A V. B. Fetisov
%A V. Ya. Mitrofanov
%A S. A. Uporov
%A L. B. Vedmid'
%J Journal of Spectroscopy
%D 2013
%R 10.1155/2013/217268
%X Oxides RBa2Cu3O6+汛 (R=Y, Nd) subjected to mechanical activation in AGO-2 mill have been studied by X-ray photoelectron spectroscopy (XPS), thermal analysis, and magnetometry. It has been shown that mechanoactivation accelerates chemical degradation under the impact of H2O and CO2 in YBa2Cu3O6+汛 samples. Degradation occurs in the standard way. Investigation of mechanically activated NdBa2Cu3O6+汛 has revealed other results. It has been suggested that CO2 can diffuse into its structure more freely than in YBa2Cu3O6+汛; as a result, carbonization may proceed directly in the volume of NdBa2Cu3O6+汛 and independently of the hydrolysis process. In addition, the mechanism of interaction between the oxide and water is not active and not ※traditional§ for the homologous series REBa2Cu3O6+汛 (where RE = rare earth and Y)〞the characteristic ※color§ phase (Nd2BaCuO5) is not formed during hydrolysis. It is known that high-temperature treatment of NdBa2Cu3O6+汛 oxide results in partial substitution of cations Ba by Nd; which is accompanied by decrease in the superconducting transition temperature and formation of the impurity phase Ba2Cu3O5+y. According to our data, mechanical activation of the resulting solid solution Nd1+xBa2ˋxCu3O6+汛 unexpectedly has led to the reverse redistribution of cations, which has been manifested in the complete disappearance of the impurity phase and increase in . 1. Introduction Compounds RBa2Cu3O6+汛 (R=Y and Ln elements) are well known as high-temperature superconductors with the temperature of the transition to the superconducting state of 90每93ˋK [1]. The composition with R=Y is a standard material for superconducting electronics under development, cooled with liquid nitrogen [2, 3], the magnetic field sensor of 羽 SQUID type [2], high current cables [4], and other products. Besides, this compound has very significant oxygen diffusion parameters, and there is an intention to use it as oxygen-ion conductor [5]. It is also known that the replacement of yttrium by neodymium results in the emergence of so-called ※anomalous peak effect§ [6], which leads to significant improvement of the superconducting transport properties of the material. An additional advantage of the oxide NdBa2Cu3O6+汛 (Nd-123) is its higher chemical stability by comparison with YBa2Cu3O6+汛 (Y-123) [7, 8]. The disadvantage of Nd-123 is ease of substitution of neodymium by barium ions in their structural positions during high temperature annealing [8每10], with the result that the temperature of the transition to the superconducting state of the solid solution Nd1+xBa2ˋxCu3O6+汛
%U http://www.hindawi.com/journals/jspec/2013/217268/