Effect of V, Nb, and Ta Doping on the 2223 Phase Formation and the Crystal Structure in the BiSrCaCuO System

✍ Scribed by Yanrong Li; Bangchao Yang; Xingzhao Liu; Youmo Li

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 213 KB
• Volume: 113
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1357

✦ Synopsis

X-ray diffraction and electrical and diamagnetic analyses revealed that the 2223 phase was significantly enhanced by highvalence cation (\left(\mathrm{V}^{5+}, \mathrm{Nb}^{5+}, \mathrm{Ta}^{5+}\right.), etc.) doping in (\mathrm{BiSrCaCuO}) samples. The optimum nominal composition was (\mathrm{Bi}{1.6} M{0.4} \mathrm{Sr}{2} \mathrm{Ca}{2} \mathrm{Cu}{3}) (\mathrm{O}{y}(M=) high-valence cations) for all three elements. A quasi-highvalence peak of (\mathrm{Cu}{2 p{3 n}}(\sim 534.5 \mathrm{eV})) has been observed. A reversible reaction, (\mathrm{Bi}^{3+} \underset{\text { anneteled }}{\text { quenched }} \mathrm{Bi}^{5+}+\mathrm{Bi}^{+}), was also encountered in the sample doped with (\mathrm{Nb}^{3+}). The effects of doping high-valence cations on the high- (T_{c}) phase formation and the crystal structure are twofold: (1) The high-valence cation substitution for the fourfoldcoordinated (\mathrm{Cu}) site in the (\mathrm{CuO}{2}) sheet strengthens the coupling among the (\mathrm{Ca}-\mathrm{CuO}{2}-\mathrm{Ca}) layers of the (110 \mathrm{~K}) phase, and (2) the cations incorporated into the Bi-O layers increase the oxygen bonding, which is beneficial for the formation of the Aurivilliustype structures and stabilizes the structure of the 2223 phase. We argue that the beneficial effect for promoting the formation of the 2223 phase might be a general property of doping with high-valence cations. 1994 Academic Press, Inc.