Tunable long lasting phosphorescence due to the selective energy transfer from defects to luminescent centres via tunnelling in Mn2+ and Tm3+ co-doped zinc pyrophosphate
Abstract
A series of new phosphors Zn2(0.97−x)P2O7:0.06Tm3+,2xMn2+ (0 ≤ x ≤ 0.05) were synthesized and their luminescence properties were investigated. The results showed that the defects in all the phosphors were related to Tm3+, and Mn2+ merely served as the emission centres. Tm3+ also acted as an emission centre and yielded blue phosphorescence corresponding to its characteristic f–f emissions in the phosphors where the Mn2+ concentration was low (x ≤ 0.001), while in the phosphors with high concentrations of Mn2+ it mainly served as a defect by forming Tm˙Zn. The electrons thermally released from defects selectively transferred to Mn2+ centres mainly through thermally-assisted tunnelling and this resulted in their red to near-infrared phosphorescence. By adjusting the ratio of Mn2+ to Tm3+ to control the spectral distribution, tunable long lasting phosphorescence from blue to near-infrared was achieved.