In this paper we examine the effect of starting composition on the formation of the two crystallographic phases characterized by c≈31 Å and c≈37 Å in the Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O systems. The superconducting properties have been studied by field-modulated microwave non-resonant absorption. The c≈37 Å phase was completely isolated in the Pb-containing system and shows a quite sharp superconductive transition at 105 K, well evidenced by the microwave absorption profile as a function of temperature. For the c≈31 Å phase, obtained in a wide range of composition, the ESR analysis points out a more complex behaviour, with a superconductive transition taking place in the 75-110 K temperature range. Strong contribution to the 110 K transition has been observed in samples showing no evidence in the X-ray spectra of the typical c≈37 Å reflections, nor of peak broadening due to stacking faults. A possible correlation of this phenomenon with the partial substitution of Bi in the Bi2O2 double layers by lighter Ca, Sr or Cu ions is discussed.

Composition Effects on the Formation and Superconducting Character of c=31 Å and c=37 Å Phases in the Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O Systems. X-Ray and ESR Analysis / Calestani, Gianluca; Rizzoli, Corrado; Andreetti, Giovanni Dario; Buluggiu, Enrico; D. C., Giori; Valenti, Alberto; A., Vera; Amoretti, Giuseppe. - In: PHYSICA. C, SUPERCONDUCTIVITY. - ISSN 0921-4534. - 158:(1989), pp. 217-224. [10.1016/0921-4534(89)90320-1]

Composition Effects on the Formation and Superconducting Character of c=31 Å and c=37 Å Phases in the Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O Systems. X-Ray and ESR Analysis

CALESTANI, Gianluca;RIZZOLI, Corrado;ANDREETTI, Giovanni Dario;BULUGGIU, Enrico;VALENTI, ALBERTO;AMORETTI, Giuseppe
1989

Abstract

In this paper we examine the effect of starting composition on the formation of the two crystallographic phases characterized by c≈31 Å and c≈37 Å in the Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O systems. The superconducting properties have been studied by field-modulated microwave non-resonant absorption. The c≈37 Å phase was completely isolated in the Pb-containing system and shows a quite sharp superconductive transition at 105 K, well evidenced by the microwave absorption profile as a function of temperature. For the c≈31 Å phase, obtained in a wide range of composition, the ESR analysis points out a more complex behaviour, with a superconductive transition taking place in the 75-110 K temperature range. Strong contribution to the 110 K transition has been observed in samples showing no evidence in the X-ray spectra of the typical c≈37 Å reflections, nor of peak broadening due to stacking faults. A possible correlation of this phenomenon with the partial substitution of Bi in the Bi2O2 double layers by lighter Ca, Sr or Cu ions is discussed.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11381/2313371
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