Incorporation of Zn²⁺ ions into Al₂O₃:Er³⁺/Yb³⁺ transparent ceramics: An effective way to enhance upconversion and near infrared emission

Al₂O₃: Er³⁺/Yb³⁺ transparent ceramics codoped with Zn²⁺ ions with intense upconversion and near infrared emission were prepared by conventional solid-state reaction and vacuum and hot isostatic pressing sintering. The effects of Zn²⁺ incorporation to the structure, transparent, upconversion and NIR luminescence were discussed in detail. The as prepared Al₂O₃ ceramics exhibited a total transmittance of ~ 75% in infrared regions (800–3300 nm) and ~ 50% in visible regions (500–800 nm). Under the excitation of a 980 nm laser diode, the as prepared Al₂O₃ ceramics displayed two tense upconversion emission peaks of a green one centered at 550 nm and a red one centered at 660 nm and a tense near infrared emission peak centered at 1.532 µm, characteristic of Er³⁺ emission. Compared with Er³⁺/Yb³⁺ doped only, Zn²⁺ codoped Al₂O₃:Er³⁺/Yb³⁺ transparent ceramics showed higher upconversion and near infrared emission of ~ 11 times and ~ 4 times, respectively. The enhancement mechanism due to incorporation of Zn²⁺ ions was also discussed in detail.