Controlled electron and hole trapping inYPO4:Ce3+,Ln3+

Abstract

A detailed and systematic electron trapping study was conducted in the scientifically important wide bandgap materials LuPO 4 and YPO 4 doubly doped with Ce 3+ and Ln 3+ ͑Ln= Sm, Dy, Ho, Er, Tm͒. By using vacuum-ultraviolet luminescence spectroscopy and detailed thermoluminescence spectroscopy it was possible to establish by two independent methods that the observed electron traps can be assigned to the Ln 3+ codoping ions. It is shown that the associated electron trap depths are determined by the energy separation between the Ln 2+ ground states and the bottom of the conduction band. Both methods reveal a systematic behavior of electron trap depths as a function of the type of Ln 3+ codoping ion that can be explained by recently developed empirical models. Small differences in trap depths obtained by the two methods are discussed in the context of charge-transfer induced relaxation processes and uncertainties in glow peak analysis. Our experiments provide valuable information on 4f n ↔ 4f n , 4f n → 4f n−1 5d, O 2− → Ln 3+ charge transfer and the lowest-energy PO 4 3− group transitions as well as electron trap depths. These transition energies allowed us to construct a complete energy-level diagram for LuPO 4 :Ln 3+/2+ and YPO 4 :Ln 3+/2+ .

Observation of intermediate bands in Eu3+ doped YPO4 host: Li+ ion effect and blue to pink light emitter

“…Band gap of YPO 4 (8.6 eV = 145 nm) is more than Eu-O charge transfer band (4.8-5.1 eV = 240-260 nm) and their band edges are crossing each other. 18 Because of defect on surface or capping ligands on particles, there is possibility to have intermediate bands, which is also supported by UV-Visible absorption measurement (Fig. 12).…”

“…16,17 Among the oxide phosphors, YPO 4 has a large indirect band gap (∼8.6 eV), high dielectric constant (∼7-10), optically isotropic with a refractive index (∼1.72), high melting point (∼1600 • C) and small phonon energy (∼1080 cm -1 ). [18][19][20][21][22] Such small vibration energy is a good choice of the host materials and will allow for effective radiative transitions between electronic energy levels of the rare earth ions in YPO 4 host. YPO 4 has tetragonal structure with space group I4 1/amd (D 19 4h , zircon type, Z = 4) and the Y 3+ ion occupies D 2d site symmetry.…”

Luminescence and x-ray absorption measurements of persistent SrAl2O4:Eu,Dy powders: Evidence for valence state changes

“…The combined radioluminescence and x-ray absorption observations are an important starting point for the construction of appropriate energy level schemes and structural models explaining the mechanism of persistent luminescence, preferably in a generic way for all Eu 2+ -based phosphors 30,31 . The model by Clabau et al 12 , where the electron is trapped at a nearby defect (presumably an oxygen vacancy) is compatible with the XANES and RL results.…”

Thermoluminescence investigation of donor (Ce3+, Pr3+, TbYou1, Bos2, Shi3 et al. 2012Phys. Rev. BSelf Cite662130View full textAdd to dashboardCite

“…11 It is also possible to activate an inorganic compound with two different lanthanide ions, which can work together as donor-acceptor pairs. [12][13][14][15] One lanthanide then acts as a donor (D) that upon photon stimulation donates an electron to the conduction band, and the other acts as an acceptor (A).…”