Control of Y₁Ba₂Cu₃Ox microstructures by polymer‐metal‐complex precursor synthesis

Single phase Y 1 Ba 2 Cu 3 O x material (1,2,3‐compound) have been synthesized from polymer‐metal‐complex (PMC) precursor between 860 and 950°C using a reaction time as short as 0.5 h. The morphology of the films and of fibers prepared by this process have been investigated. At low calcination temperatures the material is comprised of submicron grains, which are extensively interconnected forming a natural percolation network. Nodules with outgrowths are formed at intermediate temperatures; oblong shaped discs are obtained at high temperatures. The size and shape of grains are remarkably uniform in a given preparation; the former increases monotonically with the increase of calcination temperature. The 1,2,3‐compounds produced are pure according to x‐ray; they possess good superconducting properties ( T c (midpoint) = 90.6 K; Δ T c (90%‐10% resistivity) < 1 K) as prepared. Similar control of grain size and microstructure has been achieved for fibers of the 1,2,3‐compound, the mechanical strength of which is inversely related to grain size. Pure Y 2 Ba 1 Cu 2 O 5 has also been prepared by the precursor method. X‐ray diffraction gave unit cell dimension of a = 12.18 Å, b = 5.66 Å and c = 7.13 Å belong to P nma or P space group.