Bubble distribution in fused quartz crucibles studied by micro X-Ray computational tomography. Comparing 2D and 3D analysis

Abstract

Micro X-Ray computational tomography (µ-CT), has been applied to study the bubble distribution across the wall of fused quartz crucibles used for Czochralski pulling of monocrystalline silicon ingots for solar cells. Two crucibles from different suppliers has been used in the study. One set of samples was stored in water for 3 days (“wet” samples) and one set of samples was stored at 200 °C in air for 3 days (“dry” samples) prior to the first bubble analysis. Then the same samples were heated 24 h at 1400 °C and reanalysed. The µ-CT data were processed in 2D and 3D mode. The results showed that the total bubble volume was the same in 2D and 3D, while the number of bubbles was 6–9 times higher in 2D compared to 3D. The explanation was that in 2D each bubble was counted several times, while in 3D, each bubble was counted only one time. After heating the total bubble volume had increased to the double, while the number of bubbles was almost the same as in the un-heated samples. There was no significant difference in bubble size or distribution between wet and dry treated samples.