Effects of Nano-Al Doping on Superconductivity and Microstructure of MgB₂ Bulk Superconductors

Abstract

Nano-size Al powders were dispersed by ultrasonic vibrations to avoid reuniting and could be doped into the MgB2 bulk materials uniformly. The effects and mechanism of doping were studied. The phase analysis and microstructure analysis show that, Al atoms can enter into the lattice of MgB 2 and substitute the site of Mg atoms. The crystal parameters a and c of the MgB 2 phase decrease gradually with increase of Al addition, and the value of c is depressed more. The critical temperature T c drops with the increase of Al addition. The value of T c is 35.5K for the superconductor with 8mol% addition, while 38.5K for the pure MgB 2 bulk superconductor. The properties of critical current density J c (B) can be improved at low level doping such as 1mol%,2mol% addition. The results demonstrate that the superconductivity of MgB 2 with nano-Al doping is improved at the conditions of low temperature, high magnetic field and low level addition.

Measuring AC Losses and Critical Current of High Pressure Synthesized MgB₂ Bulk Rings by the Transformer Method

“…These values were estimated using the magnetization technique and Bean critical state model. The properties of bulk MgB 2 samples are crucially influenced by the preparation technology [3][4][5]. Therefore, measuring of electric characteristics (transport current and AC losses) of obtained samples is particularly important for both practical and scientific points of view.…”