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

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 CaTiO3:2Sm(3+), CaTiO3:2.5Eu(3+), and CaTiO3:2Sm(3+)/2.5Eu(3+) phosphors were found to be 0.27, 0.22, and 0.17 eV, respectively.

Automated summary

Sm3+-doped and Sm3+/Eu3+ co-doped CaTiO3 phosphor samples were synthesized and characterized. The synthesized phosphor samples exhibited orange-red and deep red emissions, which are useful for LED applications. The decrease in the lifetime of Sm3+ ions was attributed to energy transfer to Eu3+ ions.