Photoluminescence Spectroscopy and Crystal-Field Parameters of Cr³⁺ Ion in Red and Deep Red-Emitting Phosphors

The Cr 3+ -activated phosphor properties are discussed in detail from an aspect of spectroscopic point of view. The phosphor materials considered here are fluoride and oxide hosts. Such Cr 3+ -activated fluoride and oxide phosphors are classified from a different kind of spectroscopic properties of photoluminescence (PL) and PL excitation spectra. A method is proposed for obtaining reliable crystal-field ( Dq ) and Racah parameters ( B and C ) using a ligand field theory with paying an attention to difficulty in the exact estimation of such important crystal-field-related phosphor parameters. The intra- d -shell Cr 3+ states, such as 2 E g , 4 T 2 g , and 4 T 1 g , in some fluoride and oxide hosts are obtained and plotted against Dq in the Tanabe−Sugano energy-level diagram. The results are found to be in good agreement with each other.