Ceramics-Silikáty 45 (1) 9-14 (2001)

STUDY OF CRYSTALLISATION OF Al₂O₃-Fe₂O₃ GELS BY MÖSSBAUER SPECTROSCOPY

 ź. Bača, J. Lipka, I. Tóth, L. Pach 

Boehmite derived alumina gels seeded (5 wt.%) with a-Al₂O₃, a-Fe₂O₃ and Fe(NO₃)₃ were examined by Mössbauer spectroscopy. Feric oxide orginated from Fe(NO₃)₃ was identified in defect alumina phases in two high disperse form as solid solution g-(Al, Fe)₂O₃ and substituted hematite particles (a-(Fe, Al)₂O₃ ~ 6 nm). Dispersed Fe³⁺ ions reduce temperature of the crystallisation of a-Al₂O₃ (solution (Al, Fe₂O₃)) much more significantly than particulate seeds. Enhanced transformation has been attributed to solution effect of dispersed Fe³⁺ ions resulting in transparent ceramics sintered below 1300°C.