Copper ⇌ Alkali Ion Exchange of Alkali Aluminosilicate Glasses in Copper‐Containing Molten Salt: II, Divalent Copper Salts, CuCl 2 and CuSO 4

The ion‐exchange mechanism between copper and alkali ions, when 20R 2 O · 10Al 2 O 3 · 70SiO 2 (R = Li, Na, and K) glasses are immersed in divalent copper‐containing molten salts in air and nitrogen at 550°C, has been investigated. In molten CuCl 2 , the ion‐exchange behavior in both air and nitrogen was very close to that in molten CuCl in air reported previously. This is explained by assuming that CuCl 2 decomposes into CuCl and Cl 2 at 550°C and the Cu + ions thus formed mainly diffuse in glasses to replace alkali ions, where Cl 2 acts as an oxidizing agent just like oxygen. In the case of molten CuSO 4 ─ 2 SO 4 , a small amount of Cu + which is present in the molten state plays a primary role in the Cu ⇌ R + ion exchange process, although the contribution of direct Cu 2+ ⇌ 2R + ion exchange cannot be ignored.