Sol–gel-fluorination synthesis of amorphous magnesium fluoride

✍ Scribed by J. Krishna Murthy; Udo Groß; Stephan Rüdiger; Erhard Kemnitz; John M. Winfield

• Book ID: 104029451
• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 324 KB
• Volume: 179
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2005.11.033

✦ Synopsis

The sol-gel fluorination process is discussed for the reaction of magnesium alkoxides with HF in non-aqueous solvents to give X-ray amorphous nano-sized magnesium fluoride with high surface areas in the range of 150-350 m 2 /g (HS-MgF 2 ). The H2 type hysteresis of nitrogen adsorption-desorption BET-isotherms is indicative for mesoporous solids. A highly distorted structure causes quite high Lewis acidity, shown by NH 3 temperature-programmed desorption (NH 3 -TPD) and catalytic test reactions. XPS data of amorphous and conventionally crystalline MgF 2 are compared, both show octahedral coordination at the metal site. Thermal analysis, F-MAS NMRand IR-spectroscopy give information on composition and structure of the precursor intermediate as well as of the final metal fluoride. The preparation of complex fluorides, M + MgF 3 À , by the sol-gel route is reported. From the magnesium fluoride gel of the above process thin films for optical application are obtained by, e.g., spin coating.