Improved glass formation and unique structure of Bi based superconducting precursor glasses with some additives

ISSN： 0031-9090

Source： Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B, Vol.41, Iss.3, 2000-06, pp. : 158-163

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Abstract

Bi based superconducting precursor glasses with the compositions M_xBi₂Sr₂Ca₂Cu₃O_y, i.e. Bi-2223, (M=Al³⁺, Cr³⁺, Fe³⁺, Ga³⁺) are prepared to improve the glass forming ability and to get information on glass structure. The main idea for these M³⁺ ion additions comes from the presence of delafossite type compounds having the formula CuMO₂ in which two oxygen coordinated Cu+ has the role of combining octahedral MO₆ units. Additions of Al₂O₃, Cr₂O₃ and Fe₂O₃ enhance the glass formation and particularly their addition of just around x=0·8 is the most effective. The behaviour of Ga₂O₃ on glass formation in Bi-2223 is largely different from the other additives because the Ga₂O₃ addition of up to x=2·0 is effective in the glass formation. The ⁵⁷Fe Mössbauer spectra demonstrate that Fe ions in Bi-2223 glass are present as Fe³⁺ with tetrahedral coordination of oxygens. The network structure model in Bi based superconducting precursor glasses such as [BiO₆]–Cu–[CrO₆] or [BiO₆]–Cu–[FeO₄] has been proposed.