Luminescence Properties of Terbium‐Activated Rare‐Earth Oxyhalides

The luminescence properties of Tb 3+ activated rare‐earth oxyhalides (REOX, RE = Y, La, Gd, and Lu; X = F, Cl, Br, and I) are studied mainly by UV excitation. The intensities of 5 D 3,4 → 7 F J transitions and thus the emission colour are observed to depend strongly on the matrix. In addition, the energies of 5 D 3,4 → 7 F 4–6 transitions increase with increasing ionic radius of the host cation within the isomorphous REOBr series. The fine structure of the Tb 3+ spectrum is used as a structural probe on the RE oxyiodides. The energies of strong 4f → 5d absorption bands generally increase with the electronegativity of the host anion. According to the excitation spectra, efficient energy transfer occurs from the Gd 3+ ion to the Tb 3+ ion in GdOX matrices.