LI DOPING TO THE 2212-PHASE IN THE BI-SR-CA-CU-O SYSTEM

The effects of Li doping on the formation process of the 2212 phase in the Bi-Sr-Ca-Cu-O system, and its structural and superconducting feat ures were studied. Samples with nominal compositions of Bi:Sr:Ca:Cu:Li = 2: 1,5: 1.5:2: x where 0 less than or equal to x less than or equal to 0.6 were heated in air at temperatures ranging between 560 degrees C and 850 degrees C, Li doping greatly promoted the formation of the 2212 phase; the monophasic samples were rapidly obtained for x less th an or equal to 0.4 by firing even at 730 degrees C, which is about 100 degrees C lower than that of the non-doped 2212 phase. A newly found oxide phase containing Li, which was formed below 710 degrees C, is co nsidered to play an important role as a precursor to accelerate the fo rmation of the 2212 phase. The Li content in the monophasic samples de termined by ICP analysis decreased to about a half of the nominal comp osition due to partial Li escape during heating, Monophasic compositio n range of the Li-doped 2212 phase was 0 less than or equal to y less than or equal to 0.19 as Bi2Sr1.5Ca1.5Cu2LiyOz. Increase in both latti ce parameter c and oxygen content z with increasing Li content y in th e 2212 phase was accompanied with a rise of T-c up to 90 K.