Blue Persistent Phosphor of YSiO2N:Ce3+ Developed by Codoping Sm3+ or Tm3+ Ions and Thermoluminescence Analysis of Their Trap Distributions

By estimating the trap depth from the relative position of the zigzag curve of divalent lanthanoid ions and conduction band bottom, the YSiO2N:Ce3+-based blue persistent phosphors are developed, and their persistent luminescence and thermoluminescence properties are characterized to identify the electron trap distributions. Taking the nephelauxetic effect caused by covalent nitrogen into account for the vacuum referred binding energy diagram, it is predicted that Tm3+ and Sm3+ ions with the trap depth of 0.726 and 1.04 eV are an optimal codopant to obtain Ce3+ persistent luminescence. The prepared YSiO2N:Ce3+-Ln(3+) (Ln = Sm or Tm) samples enhance the Ce3+: 5d -> 4f blue persistent luminescence intensity. In the thermoluminescence glow curves, the Ce3+ singly doped sample shows two glow peaks related to intrinsic defects; on the other hand, the Ln(3+) codoped samples show an additional glow peak related to the Ln(3+) traps. The thermoluminescence glow curve analyses through the initial rise method combined with the thermal cleaning and trap density methods reveal that the electron traps of Ln(3+)-related defects have a distribution with approximate to 0.25 eV width and depths of 0.802 eV (Tm3+) and 1.10 eV (Sm3+).

Automated summary

In this study, blue persistent phosphors based on YSiO2N:Ce3+ were developed by estimating the trap depth and analyzing the trap distributions. The results demonstrate that Tm3+ and Sm3+ ions are optimal codopants to enhance the luminescence of Ce3+ in persistent phosphors.