A ceramic superconductor is produced by close control of oxygen partial pressure during sintering of the material. The resulting microstructure of YBa2Cu3Ox indicates that sintering kinetics are enhanced at reduced p(O2). The density of specimens sintered at 910 DEG C. increased from 79 to 94% theoretical when p(O2) was decreased from 0.1 to 0.0001 MPa. The increase in density with decrease in p(O2) derives from enhanced sintering kinetics, due to increased defect concentration and decreased activation energy of the rate-controlling species undergoing diffusion. Sintering at 910 DEG C. resulted in a fine-grain microstructure, with an average grain size of approximately 4 mu m. Such a microstructure results in reduced microcracking, strengths as high as 191 MPa and high critical current density capacity.