Efficient sensitization of Sm2+ emission by Eu2+ under UV excitation in Al2O3 host formed by plasma electrolytic oxidation

Al2O3 coatings doped with Sm2+ and Eu2+ ions are synthesized using plasma electrolytic oxidation (PEO) process. Photoluminescence (PL) spectra of formed coatings excited by 260 nm are composed of broad PL bands associated with Eu2+ ions in Al2O3 host with a maximum at around 405 nm and sharp bands in red region corresponding to 5D0 → 7FJ (J = 0, 1, 2) transitions of Sm2+ ions. Comparison of the emission PL spectra of Sm2+, Eu2+ and Sm2+/Eu2+ doped Al2O3 shows that the emission PL intensity of Sm2+ ions in Al2O3 host is about one order of magnitude lower than that of Sm2+/Eu2+ doped Al2O3 indicating that Eu2+ is a very efficient sensitizer for Sm2+ PL enhancement. It is also evident that an addition of Sm2+ to Eu2+ doped Al2O3 coatings causes a decrease of the Eu2+ emission, indicating that non-radiative energy transfer takes place from Eu2+ ions to Sm2+ ions.