Luminescence Spectroscopy of 3d 3 (Mn 4+ , Cr 3+ ) Ions in Multiple Octahedral-Site Phosphors

Investigating spectroscopic properties of luminescent ions in multiple sites of host materials is not only of scientific interest, but also technological importance. The present investigation focuses on this problem and reports the analysis results of the optical properties of 3 d 3 ions in the multiple octahedron sites. The phosphor materials considered are double-perovskite La 4 Ti 3 O 12 :Mn 4+ and Ca 3− x Lu x Hf 2 Al 2+ x Si 1− x O 12 :Cr 3+ ( x = 0−1.0) phosphors. An analysis method is demonstrated for obtaining reliable and site-dependent crystal-field ( Dq ) and Racah parameters ( B and C ) based on a ligand field theory with paying an attention to difficulty in the exact estimation of such important crystal-field-related parameters. For example, the difference in the crystal-field splitting energies between the slightly and highly-distorted octahedron sites determined are Δ Dq ∼ 1615 and 405 cm −1 ( x = 0) for the [MnO 6 ] 8− and [CrO 6 ] 9− octahedrons, respectively. All results are in satisfactory agreement with the Tanabe−Sugano energy-level diagram plots, promising good understanding of such 3 d 3 -ion-activated phosphors with multiple octahedron sites.