Structural transformations of nanometer sized crystals in CoO-doped beta-eucryptite-based glass-ceramics

Structural transformations of nanometer sized crystals in CoO-doped beta-eu cryptite-based glass-ceramics were studied by optical spectra and X-ray dif fraction analysis. Four types of Co(II) absorption spectra were revealed. I n the course of amorphous phase separation Co(II) ions enter into the alumi notitanate amorphous phase. Nanometer sized crystals of CoAl2O4, TiO2 and C oTiO3 precipitate at elevated temperature. The temperature reversible order -disorder phenomenon was revealed in spinel crystals. Nanometer sized disor dered crystals of beta-eucryptite solid solution precipitate after beat tre atment at 720 degrees C. At a crystallization temperature higher than 900 d egrees C, an ordering of these crystals takes place which is confirmed by t he absorption spectra and the temperature dependence of lattice parameters of the unit cell. (C) 1999 Published by Elsevier Science B.V.. All rights r eserved.