Phase and microstructure evolution in the process of the composite Bi-2212-(Sr, Ca)3Al2O6 glass-ceramics formation

Devitrification of glass with a cation ratio corresponding to the composition {Bi(2.1)Sr(2)CaCu(2)O(x) + 0.4Sr(1.7)Ca(1.3)Al(2)O(6)} was studied. At temperatures below 600 degrees C, the phases crystallized in the order Bi-2201, Cu(2)O, CaO, (Sr, Ca)(3)Bi(2)O(6), while Al ions concentrated in the remaining glass. Above 600 degrees C, Bi-2212 and (Sr, Ca)(3)Al(2)O(6) formed simultaneously, so that at 750 degrees C, the two-phase composite Bi-2212-(Sr, Ca)(3)Al(2)O(6) was obtained that contained grains of the aluminate phase 0.03-0.3 mu m in size. The Al-rich phase surplus increased the stability of the glass and accelerated Bi-2212 phase formation, while development of superconductivity in Bi-2212 was slowed down. It was shown that composite glass-ceramics with bulk superconductivity could be obtained at temperatures above 850 degrees C.