Mechanism of the Tc enhancement in Bi2Sr2CaCu2O8+y by sodium doping

✍ Scribed by Shi-Xue Dou; Wei-Min Wu; Hua-Kun Liu; Charles C. Sorrell

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 149 KB
• Volume: 185-189
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(91)91629-i

✦ Synopsis

Superconductivity in Na-doped BifirzCaCuzOs.y has been investigated and a T~ of 94 K and T, of 90 K have been achieved through the use of a melting process. A careful X-ray diffraction study on the Na-doped samples revealed that, with increasing Na content, the a and c axes increased, the b axis decreased, and the unit cell volume increased, indicating that Na was introduced into the lattice. This was further confirmed by EDS and chemical analyses. Substitution of Na for divalent atoms will reduce the oxygen content due to the requirement of charge balance, giving tL~ to an effect similar to that from quenching or during heat treatment under low oxygen partial pressures, either of which is necessary to achieve a T~ of 90 K in undoped samples.

Although a transition temperature of 90 K for BieSrzCaCu2Os÷y (2212) has been achieved through quenching samples from high temperatures or heat treating under low oxygen partial pressures (1), the T~ for 2212 is often found in the range 70 -85 K (2,3). Kawai and co-workers (4) have reported a T~ greater than 90 K for 2212 through doping with Li.