Growth of high Tc phase and structure of Ag-doped bpscco (2223) system

The effect of sintering time on the DC resistance and critical current density (J/sub c/) has been studied for Bi/sub 1.68/Pb/sub 0.32/Ag/sub x/ Sr/sub 1.73/Ca/sub 1.85/Cu/sub 2.85/O/sub 6/(x=0.0,0.6,0.8, 1.0...). The structure has been investigated by XRD and SEM. The XRD patterns revealed the intensity of the low angle peak 20=4.5 p which corresponds to the high Tc phase, increases gradually with sintering time and reaches maximum for nearly 200-240 hrs. it was also found that the percentage of the high Tc phase is around 94% and that of the low Tc is approximately 6%. The effect of silver on the structure and superconducting properties of Bi-Pb-Sr-Ca-Cu-O system has been investigated systematically. The DC resistivity measurements show that Tc(=0) varied between 100-109 K for various composition of Ag. J/sub c/ measured at LNT from I-V data shows an increase with silver addition. X-ray diffraction results showed that the dominant phase in BPSCCO is 2223. the Differential Thermal Analysis indicated the glass transition temperature, crystallization temperature and the liquid temperature of the glass are 442 deg. C, 489 deg. C and 860 deg. C respectively. The scanning electron micrographs indicated that the grain size increases with sintering time and the silver is precipitated along the grain boundaries. The silver addition enhanced the critical current density. (author)