Physico-chemical properties of ceramic high-temperature superconductors with an approximate average radius of rare earth ion(-s) obtained by a solid-state synthesis reaction

The REBa₂Cu₃O_7-δ (where RE - rare earth element, 0 < δ < 1) superconductor (also called "RE-BCO" or "1:2:3") is produced by calcination of a mixture of copper (II) oxide (CuO), barium carbonate (BaCO₃) and yttrium (III) oxide (Y₂O₃) powders. The aim of the research was to study similarities and differences in physico-chemical properties for ceramic samples of high-temperature superconductors slightly differing in the average crystal ionic radiuses of RE³⁺. For this purpose a reference sample YBa₂Cu₃O_7-δ was prepared, for which the average crystal radius of the ion Y³⁺ is 104.0 pm and two samples with approximate to that average crystal ionic radiuses RE³⁺: HoBa₂Cu₃O_7-δ and Er_0.5Dy0.5Ba₂Cu₃O_7-δ, where the average crystal ionic radiuses are 104.1 pm. The physicochemical properties of samples were studied and the microstructure of samples was characterized. The structural and phase homogeneity analysis was carried out using Raman spectroscopy, Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) technique. Raman measurements and XRD measurements revealed the presence of a superconducting phase in all studied samples. The granulation analysis of the mixture substrates powders after first and second calcination was performed with use of the Low-Angle Laser Light Scattering (LALLS) method. The magnetic properties of the obtained samples were measured with a SQUID magnetometer. The temperature dependences of AC susceptibility were used to determine the temperature of transition to the superconducting state and the hysteretic energy dissipation due to losses at inter-grain region.