Blue emission of ZrO2:Tm nanocrystals with different crystal structure under UV excitation

In this paper, thulium doped ZrO2 nanocrystals with different phases were prepared by Pechini sol–gel complex method. The effects of host structure, phases and concentration on luminescence properties of Tm3+ ions were investigated. With the increase of the concentration of Tm3+ ions, the phosphors phase transformed from monoclinic to tetragonal structure and all the phosphors emitted blue light. However, because the environment symmetry around Tm3+ in m-ZrO2 (C2h) is worse than that of t-ZrO2 (D4h), there were still obvious differences in the emission and excitation. The reason was investigated with the help of energy level diagram. In addition, the quenching concentration of Tm3+ in ZrO2 host is 1 m/m%.