Investigation of Some Ce3+-Activated Phosphors

Abstract

The fluorescence of a number of new Ce³⁺‐activated phosphors is described and discussed. Only host lattices with a sublattice consisting of trivalent lanthanide ions are used to avoid charge compensation of the Ce³⁺ ion. Usually the Ce³⁺ emission is in the near‐ultraviolet region. Y₃Al₅O₁₂–Ce and SrY₂O₄–Ce, however, show emission in the visible region with a maximum in the green. Conditions for visible Ce³⁺ emission are indicated, viz., large crystal‐field splittings (Y₃Al₅O₁₂–Ce) or a large Stokes shift (SrY₂O₄–Ce). In a number of cases we were able to observe all crystal‐field components of the excited 5d level of Ce³⁺. The cubic crystal‐field splitting of the 5d level varies strongly with host lattice from 7000 to 14 000 cm⁻¹. The position of the center of the 5d levels in oxides is about 30% lower than in the free ion. For some phosphors we observed more than one emission band at room temperature. This is due to fluorescence from higher excited levels. Efficient energy transfer from Ce³⁺ to Cr³⁺ was observed in Y₃Al₅O₁₂.