Highly enhanced green emission of Mn²⁺ in Al<inf>2</inf>O<inf>3</inf> coatings formed by plasma electrolytic oxidation via efficient Eu²⁺ → Mn²⁺ and Ce³⁺ → Mn²⁺ energy transfer

Abstract

Mn2+ single doped as well as Mn2+/Eu2+ and Mn2+/Ce3+ co-doped Al2O3 coatings were synthesized by plasma electrolytic oxidation process of aluminum and their structural, morphological, and above all, photoluminescence (PL) properties were investigated in deep. Al2O3:Mn2+ coatings exhibit a weak green PL emission centered at about 525 nm attributed to 4T1 → 6A1 forbidden transition of Mn2+. Under middle UV excitation, Eu2+ or Ce3+ single doped Al2O3 coatings show strong and broad PL emission mostly in range from 300 to 550 nm. Due to the overlap between the PL emission of Eu2+ or Ce3+ and the PL excitation of Mn2+ in Al2O3, efficient Eu2+ → Mn2+ and Ce3+ → Mn2+ energy transfer upon middle UV excitation was observed in Al2O3:Mn2+/Eu2+ and Al2O3:Mn2+/Ce3+, respectively. PL emission intensities of Mn2+ in Al2O3:Mn2+/Eu2+ and Al2O3:Mn2+/Ce3+ is two to three orders of magnitude larger than in Al2O3:Mn2+.