Review—Photoluminescence Properties of Cr3+-Activated Oxide Phosphors

The Cr 3+ -activated phosphor properties are discussed in detail from an aspect of spectroscopic point of view. The host materials considered here are a various kind of oxide compounds. The photoluminescence (PL) and PL excitation spectra of the Cr 3+ -activated oxide phosphors are analyzed based on Franck−Condon analysis within the configurational-coordinate model. A new method is proposed for obtaining reliable crystal-field ( Dq ) and Racah parameters ( B and C ) based on a general ligand field theory with paying an attention to difficulty in the exact estimation of such important ligand field parameters. The intra- d -shell Cr 3+ states, such as 2 E g ( 2 G ), 4 T 2 g ( 4 F ), and 4 T 1 g ( 4 F ), in various oxide hosts are determined and plotted against Dq in the Tanabe−Sugano energy-level diagram. The results obtained are summarized in graphical and tabular forms. A comparative discussion of Cr 3+ ion as an efficient activator in oxide and fluoride hosts is also given. The present analysis method can be used to predict an energy of Cr 3+ emission and/or to check a validity of the Racah parameter values for a variety of Cr 3+ -activated phosphors and related optical and optoelectronic device applications.