Fabrication and photoluminescence of Eu-doped KNN-based transparent ceramics

Transparent lead-free luminescent ceramics K0.47Na0.47Li0.06Nb0.94Bi0.06O3-Eu (x) (KNNLB:Eu) have been fabricated via hot-press sintering technology. The formation of perovskite KNNLB:Eu ceramics with highly densified microstructure was verified through X-ray diffraction and scanning electron microscopy studies. The transmittance spectra, photoluminescence excitation and emission spectra, dependence of the photoluminescence intensity on Eu3+ doping content as well as the luminescence decay curves were investigated. The KNNLB:Eu ceramics present high transmittance both in the near-infrared and the middle-infrared regions, and can be efficiently excited by near-ultraviolet and blue light to realize strong reddish luminescence. The red emission at around 613 nm is particularly intense, which is attributed to the electric dipole transition D-5(0)-F-7(2) of Eu3+. The PL properties are also discussed. The emission peak splitting of D-5(0)-F-7(2) transition is observed as a response to the change in crystal environment around Eu3+ in the KNNLB:Eu ceramics. With the novel intrinsic ferroelectric properties of KNN, the KNNLB:Eu ceramics could be promising candidates for multifunctional optoelectronic devices.