Upconversion emission properties of erbium- and ytterbium-doped potassium lithium tantalate niobate ceramics

We investigate the luminescence properties of erbium-doped and erbium-ytterbium-codoped potassium lithium tantalate niobate ceramics prepared by the solid phase syntheses method. The crystalline structure and surface morphology of these ceramics are tested by x-ray diffraction and scanning electron microscopy. The green, red, and near-infrared upconversion photoluminescence properties are analyzed by the steady-state spectra under 975 nm and 800 nm excitations. These ceramics are well sintered and tetragonal tungsten type crystalline structure with the 4mm point group and the P4bm space group. The Er³⁺ upconversion emission integrated intensities increase with the increase in Er³⁺ ion concentration, while the green emission decreases with the increase in Yb³⁺ ion concentration under the 800 nm excitation. An effective energy back transfer process from the Er^{3+ 4}S_3/2 state to Yb³⁺ ground state plays an important role in enhancing the red emission and weakening the green emission.