Effect of Na2O Addition on the Optical Properties and Chemical Durability of Li2O–CaO–Al2O3–GeO2 Glass

Abstract

By progressive weight percent substitution of Na2O for Li2O, at a constant ratio of concentration of CaO, Al2O3, and GeO2, the Li2O(–Na2O)–CaO–Al2O3–GeO2 system is prepared for infrared transmitting germanate glasses. The optical and chemical durability properties of these glasses have been studied. The infrared cutoff for these germanate glasses is about 7.2 µm longer than that of 5 µm for silicate glasses. The ultraviolet absorption edge for these glasses is near 306 nm, except for the glass which contained 6.44 wt% Na2O at 295 nm. The refractive indexes of these germanate glasses increase as Na2O content is increased. The Abbe number for all glass samples is about 62.03±4.07. The absorption coefficients for these germanate glasses at 2.5 µm and 500–700 nm are 0.023 mm-1 and 0.019 mm-1, respectively. The leaching results indicate that the glass with 3.22 wt% Na2O ( C3 glass) has the minimum weight loss in the chemical durability test.