The effect of the treatment time in diluted water on the superconducting properties of MgB₂

MgB₂ powders were treated for different amount of time in diluted water (water-ethanol mixture) with two different water-to-ethanol ratios of 12 : 18 and 6 : 24 to investigate the effect of diluted water-treatment on the superconducting properties of MgB₂. The diluted water-treatment did not affect the phase composition of the powder. The magnetic moment measurement of both untreated and treated MgB₂ powders showed the degradation of irreversible magnetic moment of the powders as the treatment time increases. The change of irreversible magnetic moment was explained by the dissolution of Mg and B into the diluted water during the treatment. The amount of dissolved substances after the treatment measured by chemical analyses (ICP MS) showed that the concentration of B dissolved in the diluted water is much larger than that of Mg, as the treatment time increases. The contact of MgB₂ with the water or moisture has to be considered in the design of the superconducting devices based on the MgB₂ to prevent the degradation of the superconducting properties of the devices.