الملخص
In this study, the effect of yttrium substitution by cadmium in the YBa2Cu4O8 superconductor was investigated. A series of superconducting oxide ceramics of (Y1- xCdx)Ba2Cu4O8 with different Cd content (x = 0.00-0.18 mol) were prepared by aqueous sol–gel method using aqueous mixtures of the metal acetates. Homogeneous precursor gels were obtained by complexing copper ions with tartaric acid. The obtained gel powders and end products were characterized by X-ray powder diffraction analysis, infrared spectroscopy, thermogravimetric, differential thermal analysis, scanning electron microscopy, energy of dispersive X-ray analysis, DC-electrical resistivity, and magnetic susceptibility measurements. The gel synthesized was amorphous and highly homogeneous. Single-phase bulk samples were obtained after annealing at 1108 K for 100 h, in an atmospher of flowing O2 gas. XRD measurements indicated that the crystal structure remains orthorhombic (up to x = 0.12 mol). With further increase of the cadmium substitutional level, peaks of Y-124 phase disappeared. Doping the YBa2Cu4O8 phase with cadmium showed a strong effect on the superconducting properties increasing the critical temperature (Tc) from 80 K (for non-substituted sample) to 92 K (for the (Y0.88Cd0.12)Ba2Cu4O8), and Tc decreases with further increase of cadmium substitutional level. Also prepared a series of (Y1-xCdxBa2Cu4O8) samples with (0.0 ≤ x ≤ 0.08 mol), via ceramic method and annealing at 1123 K for 132 h in an atmospher of flowing O2 gas. The characterization of the final products was conducted by X-ray diffraction, scanning electron microscopy, and energy dispersive...
