Photoluminescence Properties of Pr-Doped (Ca,Sr,Ba)TiO₃

Photoluminescence properties of Pr-doped alkaline-earth titanates Pr 0.002 (Ca,Sr,Ba) 0.997 TiO 3 are investigated by emission, excitation, and diffuse reflectance spectra at room temperature. The intensities of red luminescence and absorption due to f − f transition of Pr 3+ ions increase in the order of Pr-doped cubic SrTiO 3, tetragonal BaTiO 3, and orthorhombic CaTiO 3 . The small red luminescence for Pr-doped SrTiO 3 is increased by substituting Sr by Ca and Ba even if the substituted samples have the same cubic structure as SrTiO 3 and the lattice parameters are close to that of SrTiO 3 . The red luminescence intensity is intense for orthorhombic samples of which the excitation spectra show a peak corresponding to valence-to-conduction band edge and a shoulder referred to as B band. The photoluminescence properties are discussed in relation to the crystal structure.