Self-organized nano-crystallisation of BaF2 from Na2O/K2O/BaF2/Al2O3/SiO2 glasses

✍ Scribed by Christian Bocker; Christian Rüssel

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 398 KB
• Volume: 29
• Category: Article
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2008.08.005

✦ Synopsis

In glasses with the compositions (100x)(2Na 2 O•16K 2 O•8Al 2 O 3 •74SiO 2 )xBaF 2 (with x = 0 to 6), the glass transition temperature decreases with increasing BaF 2 -concentration. Samples with x = 6 were thermally treated at temperatures in the range from 500 to 600 • C for 5-160 h. This leads to the crystallisation of BaF 2 . The quantity of crystalline BaF 2 increases with increasing time of thermal treatment, while the mean crystallite size remains constant within the limits of error. The glass transformation temperature of partially crystallised samples increases with increasing crystallisation time and approaches a value equal to the temperature, at which the samples were treated. This is explained by the formation of a highly viscous layer enriched in SiO 2 which is formed during crystallisation. This layer acts as a diffusion barrier and hinders further crystal growth.