Investigation of electrical and magnetic properties of Bi-2212 superconducting materials prepared by hot press method

Bi2Sr2Ca1Cu1.75Na0.25Oy ceramics have been prepared by the classical solid state reaction method followed by hot-pressing process under several applied pressures and temperatures: 22 and 33 MPa at 750 °C, and 22 MPa at 800 °C. The superconducting properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), dc electrical resistivity (R-T) and magnetic hysteresis (M-H) measurements. In addition to the formation of secondary impurity phases such as Bi2CaO4 and Bi3Sr4CaCu3O4 in all samples, it is seen that the basic phase is Bi2Sr2Ca1Cu2Oy (Bi-2212) in X-ray diffraction measurements. The best grain orientation was obtained in the sample at 750 °C with a pressure of 33 MPa. The Tcoffset values of the samples were measured as 87.5, 85, 65 K for samples A, B, C, respectively, and the highest Tcoffset value was obtained in sample B. Due to the development of microstructural properties, the widest M-H curves were reached in sample B. In the scope of this study, the highest critical current density value was obtained in the sample prepared by applying 33 MPa at 750 °C (201.5 × 104 A/cm2 at 1.9 T and 15 K) at a much higher level than the values reported in the literature for samples with a similar composition prepared by the solid state method.