Structure, photoluminescence properties, and energy transfer phenomenon in Sm3+/Eu3+ co-doped CaTiO3 phosphors

Abstract

Sm³⁺-doped and Sm³⁺/Eu³⁺ co-doped CaTiO₃ phosphor samples were synthesized by solid-state reaction method and characterized using XRD, FE-SEM, FTIR, XPS, UV visible absorption, and photoluminescence techniques. All the compounds showed a crystalline structure with an orthorhombic phase and Pnma(62) space group. The diffuse reflectance spectra showed an absorption band due to the host along with peaks for Sm³⁺ and Eu³⁺ ions. The photoluminescence emission spectra of Sm³⁺-doped CaTiO₃ phosphor showed orange-red and deep red emissions on excitation with 407 nm in which the peak at 599 nm was of maximum intensity. Similarly, Eu³⁺ ions showed a maximum intensity peak at 613 nm on excitation with 398 nm wavelength. The Sm³⁺/Eu³⁺ co-doped CaTiO₃ phosphor showed an energy transfer from Sm³⁺ to Eu³⁺ ions on excitation with 407 nm and the nature of interaction between them was found to be dipole–dipole type. The CIE color coordinates and the correlated color temperature (CCT) calculations of the phosphors were performed, which showed an orange-red color emission useful for LED applications. The lifetime of Sm³⁺ ions decreases in the presence of Eu³⁺ ions and this was due to energy transfer from Sm³⁺ to Eu³⁺ ions. The temperature-dependent PL spectra of the phosphors showed thermal quenching behaviour. The activation energy of CaTiO₃:2Sm³⁺, CaTiO₃:2.5Eu³⁺, and CaTiO₃:2Sm³⁺/2.5Eu³⁺ phosphors were found to be 0.27, 0.22, and 0.17 eV, respectively.