Effect of Y:Zn ratio on microstructure and emission of Er3+/Yb3+ codoped Y2O3–ZnO ceramic phosphors

In this study, Er 3+ /Yb 3+ codoped Y 2 O 3 –ZnO ceramic phosphors were prepared by sol–gel method. The samples had two emission bands, namely, green (535 nm) and red (660 nm), which are attributed to Er 3+ : 2 H 11/2 ( 4 S 3/2 ) → 4 I 15/2 and Er 3+ : 4 F 9/2  →  4 I 15/2 radiative transitions , respectively. The samples exhibited green- and red-emission intensity enhancement by 1.728 and 2.286 times that of the pure Y 2 O 3 host, respectively and by 514.468 and 214.341 times that of the pure ZnO host. The emission intensities are first enhanced by lattice expansion. With the change of Y:Zn ratio, the high surface energy is converted into low crystal surface resulting in the change of asymmetry crystal field for matrix. When the intensity of the asymmetric crystal field reaches maximum, both emissions are further boosted. When the high surface energy transforms into crystal surface energy, the microstructure changes into a compact mesoporous structure. Consequently, the chemical stability of the samples improves significantly, and the final emission band of the three samples with mesoporous structures is continuously red.