Solid-phase reactive inter-diffusion of Mg/B multilayers

摘要

A better understanding of the reaction of Mg and B in the solid-phase regime is needed for the low-temperature synthesis of MgB2 films. Here, we study the kinetics of reactive inter-diffusion of Mg and B multilayers on glassy carbon substrates in the temperature range of 400-650 degrees C. Results show that, at these temperatures, inter-diffusion is characterized by a single activation energy of similar to 0.45 eV. The formation of the superconducting MgB2 phase with critical temperatures of 25-31 K occurs at reaction temperatures of 450 degrees C and above, with the rate of inter-diffusion obeying a power law with a kinetic exponent of similar to 0.3. This suggests that rate-limiting processes are the nucleation and growth of MgB2 grains rather than diffusion and interfacial reactions. Implications of these results to the low-temperature synthesis of MgB2 films are discussed. Published under license by AIP Publishing.