Interdiffusion of Calcium in Soda‐Lime‐Silica Glass at 880° to 1308°C

The interdiffusion of calcium in soda‐lime‐silica glass under the action of a concentration gradient was studied. Pairs of glass blocks differing by 2.9 mole % in CaO content were fused together to form diffusion couples and were held at 880° to 1308°C. The couples were allowed to cool to room temperature and the diffusion which had taken place was measured by optical interferometry and by an electron microprobe. The diffusion coefficients varied from 4.4 × 10 −10 cm 2 /sec at 880°C to 8.0 × 10 −8 cm 2 /sec at 1308°C. The activation energy was 42,000 cal/mole. It is concluded that oxygen diffuses simultaneously with the calcium, maintaining the electrical neutrality of the glass.