Determination of the solid solubility of SrAl2o4 in CaAl2o4 through crystal field-dependent Eu2+ signatures

The solid solubility of the SrAl2O4–CaAl2O4 system was investigated. Both XRD patterns and cathodoluminescence from Eu2+ in the host lattices were utilized to investigate the solid solubility of SrAl2O4 in CaAl2O4. A single phase exists in the range x = 1 to x = 0.5 in Sr1−xCaxAl2O4 composition (i.e., the [CaAl2O4] phase exists as a single phase from CaAl2O4 to Sr0.5Ca0.5Al2O4). The luminescence band maximum of Eu2+ in [CaAl2O4] phase shifts from 433 nm (CaAl2O4:Eu2+) to 404 nm (Sr0.9Ca0.1Al2O4:Eu2+). The blue-shift behavior of Eu2+ emission can be explained in terms of Eu2+ experiencing the weakening of crystal field strength with the decreasing x value of Sr1−xCaxAl2O4:Eu2+ (0.01%). This phenomenon confirms that Blasse’s prediction regarding the Eu2+ crystal field-dependent 4f65d1 energy level is applicable in oxide hosts.