Non-matrix matched quantification of doped and pure magnesium diboride by UV nano- and femtosecond LA-ICP-MS

Complete text of publication follows. The critical temperature for superconductivity in magnesium diboride (MgB2), discovered in 2001 by Nagamatsu et al (J. Nagamatsu et al., Nature, 410 (2001) 63-64), is the highest among the so-called conventional superconductors. Therefore, this material has experienced a huge interest over the last few years. Different efforts have been made to raise the critical temperature by doping the MgB2 crystals with different elements, e.g. Li, Al, C or Zr (J. Karpinski et al., Physica C, 456 (2007) 3-13). In this study, the analysis of such crystals by UV nano- and femtosecond laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was performed and the results were compared with X-ray diffraction measurements. Due to the lack of a suitable matrix matched standards, a non-matrix matched one, NIST SRM 610, had to be used for the LA-ICP-MS measurements like shown before (V. Mozna et al., J. Anal. At. Spectrom., 21 (2006) 1194-1201). Nanosecond LA-ICP-MS suggested a change in stoichiometry from MgB2 to MgB whereas femtosecond LA-ICP-MS resulted in the expected composition, i.e. MgB2, which was, in addition, confirmed by X-ray diffraction. Furthermore, lithium and aluminum doped MgB2 crystals were analyzed to measure the doping percentage. In some lithium doped crystals an enrichment of both lithium and magnesium on the surface was observed. This study demonstrates the advantage femtosecond LA-ICP-MS offers for the analysis of conducting samples over nanosecond LA-ICP-MS.