Mechanical Grinding and Reforming Process of the BI-2201 Phase (II) —Comparing the Various BI-2201 Solid Solutions—

Mechanical grinding and the reformation from ground powder of the “2201” phase doped Pb, Ca and Ba were examined by XRD and DTA. The “2201” solid solutions changes easily into fine powder by mechanical grinding. The Ca-or Ba-substitution for Sr tends to suppress the formation of SrCO₃ from the ground powder on mechanical grinding in air. The formation of Bi₂CuO₄ at 400°C and the reformation of the original “2201” phase at 800°C seem to be common for the “2201” solid solutions. The ground powder consists of not amorphous powder but ultra-fine crystals. Each crystal has a diameter of 30 to 100 Å and a thickness of one unit cell or a half unit cell length and thermally unstable.