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)TiO3 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 Pr3+ ions increase in the order of Pr-doped cubic SrTiO3, tetragonal BaTiO3, and orthorhombic CaTiO3. The small red luminescence for Pr-doped SrTiO3 is increased by substituting Sr by Ca and Ba even if the substituted samples have the same cubic structure as SrTiO3 and the lattice parameters are close to that of SrTiO3. The red luminescence intensity is intense for orthorhombic samples of which the excitation spectra show a peak corresponding to valenceto-conduction band edge and a shoulder referred to as B band. The photoluminescence properties are discussed in relation to the crystal structure.