Synthesis of YBa2Cu3O7−δ with clean grain boundaries by a modified aerosol decomposition process

Abstract

A modified aerosol decomposition method was developed for producing sintered YBa2Cu3O7−δ (1-2-3) pellets having sharp superconducting transition Tc's at ∼90 K, fine grain sizes, and clean grain boundaries. This method used “precursor” powders, which were produced with an aerosol flow reactor at 550 °C, instead of in situ produced 1-2-3 powders commonly processed at 880–1000 °C. As determined by x-ray absorption and powder diffraction studies, the 1-2-3 powders produced by the modified route contain less cation disorders than the in situ produced powders. The disorder is speculated to be the cause of Tc-suppression and broadening. It cannot be removed unless high sintering temperatures were used (>950 °C), which resulted in large grains and impurities and cracks at grain boundaries.