Green and red upconversion luminescence of Er3+-doped K0.5Na0.5NbO3 ceramics

Abstract Er 3+ doped K 0.5 Na 0.5 NbO 3 (KNN) lead-free piezoelectric ceramics were synthesized by the solid-state reaction method. The upconversion emission properties of Er 3+ doped KNN ceramics were investigated as a function of Er 3+ concentration and incident pumping power intensity. Bright green (~555 nm) and red (670 nm) upconversion emission bands were obtained under 980 nm excitation at room temperature, which are attributed to ( 2 H 11/2 , 4 S 3/2 )→ 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions, respectively. The upconversion emission intensity can be adjusted by changing Er 3+ concentration, and the mechanism of upconversion processes involve not only a two-photon absorption but also a three-photon absorption. In addition to the admirable intrinsic piezoelectric properties of KNN, this kind of material may have potential application as a multifunctional device by integrating its upconversion and piezoelectric property.