Surface chemistry of group IIA and IIIB fluorides in air by diffuse reflectance spectroscopy

The compounds forming on the surface of MgF2, SrF2, BaF2, ScF3,YF3, and LaF 3 during storage in air were identified by Fourier-transform IR diffuse ref lectance spectroscopy. The adlayer on the surface of MgF2 was found to cont ain magnesium hydroxide; on the surface of BaF2, YF3, and LaF3, basic carbo nates were present. The mechanisms of the possible surface reactions are di scussed, and a procedure is proposed which allows one to replace hydroxide- carbonate surface groups by fluoride groups and to enhance the stability of the fluoride surface to atmospheric attack.