Time-resolved spectroscopy of exciton states in single crystals and single crystalline films of YAlO₃ and YAlO₃ : Ce

Abstract

Luminescence characteristics of single crystals (SC), single crystalline films (SCF), powders and ceramics of YAlO 3 and YAlO 3 :Ce have been studied at 4.2-300 K under photoexcitation in the 4-20 eV energy range and X-ray excitation. The origin and structure of defects responsible for various exciton-related emission and excitation bands have been identified. The ~5.6 eV emission of YAlO 3 SCF is ascribed to the self-trapped excitons. In YAlO 3 SC, the dominating 5.63 eV and 4.12 eV emissions are ascribed to the excitons localized at the isolated antisite defect Y 3+ Al and at the Y 3+ Al defect associated with the nearest-neighbouring oxygen vacancy, respectively. Thermally stimulated release of electrons, trapped at these defects, takes place at 200 K and 280 K, respectively. The formation energies of various Y 3+ Al-related defects are calculated. The presence of Y Al antisite-related defects is confirmed by NMR measurements. The influence of various intrinsic and impurity defects on the luminescence characteristics of Ce 3+ centers is clarified. The assumption about effective formation of the {Y 3+ Al-V O }-type defects in YAP SC is supported also by the comparison of the Y 3+ Al and {Y 3+ Al-V O } defects formation energies. 3.3. Calculation of the Y 3+ Al , {Y 3+ Al-V O }, and {Y 3+ Al-Ce 3+ } defects formation energies Ab-initio computations allow determination the total energies as a function of ionic coordinates and types of ions, and thus provide independent information about the microscopic structure of a defect and clarify some models of defects. The density functional theory (DFT) calculations were performed by us within the local spin-density approximation (LSDA). We have used the all-electron full-potential local-orbital

Electron spin resonance of paramagnetic defects and related charge carrier traps in complex oxide scintillators

“…Two strong lines correspond to resonances from regular Y ions, while two other weak lines correspond to Y in antisite positions. (b) 27 Al static (inset) and MAS NMR spectra measured in ground YAP SC and commercial powder 31: (a) ground SC, spinning rate (SR) 10 kHz; (b) ground SC, SR 14 kHz; (c) powder, SR 14 kHz. The strong line at 10 ppm corresponds to resonance from regular Al ions in the AlO 6 octahedral coordination, while weak resonance at 50 ppm corresponds to Al in fivefold coordination.…”

Effect of Lutetium Co-Doping on the Main Dosimetric Peak of YAP:Mn2+ Thermoluminescent Detectors

“…Al electron centers are thermally destroyed at temperatures below room temperature [10]. However, in accordance with [11,12], the EPR signal associated with Y 2+…”

Band Gap Engineering and Trap Depths of Intrinsic Point Defects in RAlO3 (R = Y, La, Gd, Yb, Lu) Perovskites

“…Note that the above-mentioned results demonstrate how the BGE approach can be applied on purpose to move from the long-time storage phosphor, like YAlO 3 :Mn, 5,49,50,67 to the efficient persistent luminescence phosphor, like (La−Gd)-AlO 3 :Mn (known from Du et al). 55 At the same time, it is obvious that the following questions should be answered in order to clarify the origin of the tendency observed in TSL.…”