Sulphur precipitation in annealed sulphur-doped nickel studied by fluorescent X-ray emission

The results of measurements of S L-2,L-3 ultra-soft X-ray emission spectra excited by synchrotron radiation at h upsilon=163-165 eV for samples with 240 ppm S in Ni after annealing at 400-700 degrees C are presented. It is found that S L2,3 X- ray emission spectra of S-impurity atoms in Ni show fine structure which can be simulated by a superposition of spectra of nickel sulphide and pure sulphur providing evidence that sulphur atoms are present after annealing both in solid solution and in clusters where they form S-S bonds. The variation of temperature and time of annealing (at T= 400 degrees C for 1 h and at T=700 degrees C for 2 h) leads to some redistribution of intensity of S L-2.3 X-ray emission valence spectra which can be attributed to changes in the number of S-Ni and S-S bonds in accordance with the limit of sulphur solubility at these temperatures.