A Highly Enhanced Photoluminescence of Eu 3+ -Activated CaTiO 3 Phosphors via Selective A-Site and B-Site Cation Substitutions (Sr 2+ and Sn 4+ )

Sr 2+ and Sn 4+ doped CaTiO 3 :Eu 3+ phosphors were prepared by a high temperature solid-state method. X-ray diffraction characterization shows that the sample calcined at 1200°C is pure and has an orthorhombic crystal lattice. Photoluminescence (PL) measurement shows that CaTiO 3 :Eu 3+ has five excitation peaks at 363 nm, 381 nm, 398 nm, 418 nm, and 466 nm, respectively corresponding to the transitions 7 F 0 → 5 D 4 , 7 F 0 → 5 L 7 , 7 F 0 → 5 L 6 , 7 F 0 → 5 D 3 and 7 F 0 → 5 D 2 of Eu 3+ . The main emission peaks of CaTiO 3 :Eu 3+ at 592 nm and 613 nm are ascribed to the 5 D 0 → 7 F J ( J = 1, 2) transitions of Eu 3+ . In addition, PL emissions at 592 nm and 613 nm of CaTiO 3 :Eu 3+ phosphors are enhanced remarkably through A-site substitution of Ca 2+ with Sr 2+ or B-site substitution of Ti 4+ with Sn 4+ . Noticeably, the emission intensity of Ca(Ti,Sn)O 3 :Eu 3+ is nearly three times higher than that of CaTiO 3 :Eu 3+ . The reason is that substitution of Ti 4+ with Sn 4+ induces a large lattice distortion, which promotes the 5 D 0 → 7 F 2 transition probability and thus enhances the emissions at 613 nm. It is also found that Sr 2+ substitution narrows the optical bandgaps of CaTiO 3 :Eu 3+ , while Sn 4+ substitution widens them. In addition, chromatic purity of the phosphors shows a remarkable dependence on the asymmetric ratio.