Investigation on Relationship between Charge Transfer Position and Dielectric Definition of Average Energy Gap in Eu³⁺-Doped Compounds

The dielectric definition of average energy gap E g of the chemical bond has been calculated quantitatively in Eu 3+ -doped 30 lanthanide compounds based on the dielectric theory of chemical bond for complex structure crystals. The relationship between the experimental charge transfer (CT) energy of Eu 3+ and the corresponding average energy gap E g has been studied. The results show that the CT energy increases linearly with increasing of the average energy gap E g . The linear model is obtained. It allows us to predict the CT position of Eu 3+ -doped lanthanide compounds with knowledge of the crystal structure and index of refraction. Applied to the Ca 4 GdO(BO 3 ) 3:Eu and Li 2 Lu 5 O 4 (BO 3 ) 3:Eu crystals, the predicted results of CT energies are in good agreement with the experimental values, and it can be concluded that the lowest CT energy in Li 2 Lu 5 O 4 (BO 3 ) 3:Eu originates from the site of Lu1.