Soda-lime glass with gradient of refraction index (GRIN)

In a soda-lime glass provided by Companhia Vidraria Santa Marina, subsidiar y of French Saint-Gobain, we induced a gradient of refraction of index (GRI N) by exchange of Na+ in glass by Li+ at 550 degreesC for 12, 24, 36 and 48 hours and varying bath temperature at 525 degreesC, 550 degreesC, 575 degr eesC and 600 degreesC for fixed time of 48 hours. Deltan = 0.0107 +/- 0.000 5 and GRIN depth of about 2.4mm were obtained for the ion exchange at 550 d egreesC for 48 hours. The GRIN profile was fitted with erfc(x) function and then obtained the diffusion coefficient D = (1.6 +/- 0.3) . 10(-6) mm(2)/s .