[en] A method of producing a high temperature ceramic superconductor is described comprising the steps of: providing core pellets of pressed particles of metal oxides selected from the group consisting of Bi.Sr.Ca.Cu.O and Bi.Pb.Sr.Ca.Cu.O, placing the pellets within a metallic sheath, thereby forming a sheath-pellet structure, reducing the cross-section of the sheath-pellet structure, thereby providing a composite comprising said metallic sheath and a ceramic oxide core, and heat treating the composite, sealing the composite in a container assembly, having a high temperature resistant compression/separation medium containing 40% to 95% of a porous material selected from the group consisting of particulate material and fibrous material, and a thin metal outer portion surrounding the metallic sheath, under vacuum conditions, thereby placing the core under vacuum to ease compression thereof, and then hot isostatically pressing the composite through the compression/separation medium at from 352 kg/cm² to 3,172 kg/cm², and at a temperature over 600 C. thereby initiating melting of the ceramic oxide core but not of the metallic sheath while causing plastic flow of said metallic sheath, and thereby causing from 1% to 20% reduction in the cross-section of the composite and intimate contact between the core and the sheath at their interface while compressing said core to near its theoretical density and thus eliminating voids therein, and then, composite and compression/separation medium, and then annealing the composite in a source of oxygen, at a temperature from 770 C to 870 C for 40 hours to 200 hours, thereby maximizing current density of the core