Discovery of the Persistent Luminescence Mechanism of CdSiO₃:Tb³⁺

Abstract

The persistent luminescence of CdSiO 3:Tb 3+ was investigated with photoluminescence, thermoluminescence (TL), synchrotron radiation X-ray absorption (XANES and EXAFS) and UV-VUV spectroscopies. Only the typical intraconfigurational 4f 8 –4f 8 transitions of the Tb 3+ ion were observed with no traces of band emission in either the conventional UV excited or persistent luminescence spectra. The trap structure from TL with three traps from 0.65 to 0.85 eV is ideal for room-temperature persistent luminescence similar to, e.g., Sr 2 MgSi 2 O 7:Eu 2+,R 3+ . Despite the rather low band gap energy, 5.28 eV, the persistent luminescence from Tb 3+ is produced only under UV irradiation due to the inauspicious position of the 7 F 6 ground level deep in the band gap of CdSiO 3 . This confirms the role of electrons as the charge carriers in the mechanism of Tb 3+ persistent luminescence. The XANES spectra indicated the presence of only the trivalent Tb 3+ species, thus excluding the direct Tb 3+ → Tb IV oxidation during the charging process of persistent luminescence. Eventually, a unique persistent luminescence mechanism for Tb 3+ in CdSiO 3 was constructed based on the comprehensive experimental data.