Analysis of impurity effects on the coloration of corundum by laser-induced breakdown spectroscopy (LIBS)

Corundum was analyzed using laser-induced breakdown spectroscopy (LIBS) for impurity effects in their multiple colorings. Qualitative measurements were attained for impurities of chromium, magnesium, iron, and titanium in red, yellow, and blue samples. Moreover, treatment with a beryllium diffusion, which can modify corundum to obtain an attractive color, was tested in the yellow sample. In this work, most of the measurements were acquired using a laser pulse energy of 5 mJ and impurity emissions were appreciable. The signal-to-noise ratios were 11, 6.5, 10, and 4 for the Cr 425.44 nm, Fe 404.58 nm, Be 313.04 nm, and Mg 285.21 nm lines, respectively, for five laser shots. The amount of damage to the corundum samples was also monitored by measuring the craters after laser analysis. It was found that the crater size was about 30 μm after 10 laser shots. As such, the damage to corundum sample is almost imperceptible after the LIBS analysis.