Catalytic effects of Ag2O additives on microstructure and recrystallization in borate glasses

A substitution of Ag2O for B2O3 in a 35BaO–25Fe2O3–(40−x)B2O3–xAg2O, x=0.0, 0.5, 1.0 and 3.0, glass series modifies the B2O3 network and changes infrared frequencies in the 1600–600 cm-1 region. Four bands at 1440, 1280, 1180 and 1120 cm-1 appear in glass containing no Ag2O additive. On adding the Ag2O, the 1120 cm-1 band (which belongs to the BO3→BO4 modified group in the B2O3 network) no longer appears, and the other three bands (belonging to the B–O stretching vibrations in the interconnected boroxol rings) shift 15–40 cm-1 to higher frequencies expected in the reduced structural defects of BO3→BO4 modified groups and non-bridging oxygens. This modified glass crystallizes (at 500–850°C) into acicular BaFe12O19 microcrystals of a higher coercivity of ∼5000 Oe, suitable for high energy-density magnets and other devices. This revised version was published online in November 2006 with corrections to the Cover Date.