Crystallization of Mullite from Kaolin According to Optical Spectroscopy of Impurity Ions

摘要

The luminescence spectra of Cr3+ and Eu3+ ions embedded in mullite ceramic samples are studied. The samples were annealed at temperatures from 600 to 1200 degrees C. Beginning at a temperature of 890 degrees C, the spectra demonstrated the presence of a newly formed crystal phase. At temperatures from 920 to 1200 degrees C, the crystalline form manifested itself as a stable mullite phase. A temperature of 920 degrees C. corresponded to a sharp change in the symmetry of the crystal field around Eu3+ ( phase transition). The parameters of the spectral lines of ions were used to estimate the mullite crystal-lattice disorder and the residual deformations in ceramic samples. The spread of the mullite crystal-lattice parameter is determined as |Delta a/a| approximate to 0.028 and is independent of the annealing temperature.