DETERMINATION OF THE SOLID SOLUBILITY OF SrAI_2O_4 IN CaAl_2O_4 THROUGH CRYSTAL FIELD-DEPENDENT Eu~2+ SIGNATURES

摘要

The solid solubility of the SrAl_2O_4-CaAl_2O_4 system was investigated. Both XRD patterns and cathodoluminescence from Eu~2+ in the host lattices were utilized to investigate the solid solubility of SrAl_2O_4 in CaAl_2O_4. A single phase exists in the range x = l to x = 0.5 in Sr_1-x Cax-Al_2O_4 composition (i.e., the [CaAl_2O_4] phase exists as a single phase from CaAl_2O_4 to Sr_0.5Ca_0.5Al_2O_4). The luminescence band maximum of Eu~2+ in [CaAl_2O_4] phase shifts from 433 nm (CaAl_2O_4:fEu~2+) to 404 nm (Sr_0.9Cao_0.1Al_2O_4:Eu~2+). The blue-shift behavior of Eu~2+ emission can be explained in terms of Eu~2+ experiencing the weakening of crystal field strength with the decreasing x value of Sr_1-xCaxAl_2O_4fEu~2+ (0.0l/100). This phenomenon confirms that Blasse's prediction regarding the Eu~2+ crystal field-dependent 4f5d energy level is applicable in oxide hosts.