Effect of Li doping on the O vacancies in Lu2SiO5:Ce phosphors

Jia, Lingchun; Zhu, Jiajie; Teng, Yunxue; Gu, Ming

doi:10.1016/j.matlet.2018.06.051

Cited by 13 publications

(7 citation statements)

References 15 publications

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“…Then, it is inferred that the formation of the Yb 2+ ions at the original Yb 3+ site promotes the generation of a defect with positive charges, i.e., V O ·· , to imbalance the negative charge inside the lattice, leading to the dramatic enhancement in the TL intensity. Similar analyses have been extensively reported in the YAG host ,, and other hosts. ,− Contrary to Yb 3+ , Ce 2+ with the electron configuration [Xe]4f 1 5d 1 is less stable because neither the 4f subshell nor the 5d subshell is half-filled or completely filled, hence making it difficult to reduce Ce 3+ into Ce 2+ . Without Yb as a stabilizer, charge neutrality inhibits mass generation of positive defects including the V O during the reducing heating, resulting in the insignificant increase in TL intensity of the reduced singly doped sample.…”

Section: Resultssupporting

confidence: 75%

Effect of Oxygen Vacancies on the Persistent Luminescence of Y₃Al₂Ga₃O₁₂:Ce³⁺,Yb³⁺ Phosphors

et al. 2021

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The effect of oxygen vacancies (V O ) and the atmosphere influence on persistent luminescence (PersL) in Y 3 Al 2 Ga 3 O 12 (YAGG):Ce 3+ ,Yb 3+ are investigated by heating it in CO 2 , air, and 10% H 2 /90% Ar atmospheres. The V O -rich YAGG phosphors with outstanding PersL are successfully obtained by the common contribution of the reducing atmosphere and the incorporated Yb 3+ ions, and the concentration of oxygen vacancies in the phosphors is characterized by X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements. Compared to the best sample prepared in neutral CO 2 , the reduced sample shows an increase of 30% in initial intensity and 100% in duration time, while the oxidized sample decreases drastically and shows a faint and undetectable PersL. The enhancement is mainly caused by the abundant formation of V O , which is achieved by the pairing of V O with Yb 2+ ions. The newly created V O by the reducing calcination is inferred to be adjacent to the Yb site and forms a compensation-type defect cluster due to the charge compensation effect. These findings reveal that understanding the effect and formation of V O is of great significance to design a high-performance phosphor.

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Section: Resultssupporting

confidence: 75%

Effect of Oxygen Vacancies on the Persistent Luminescence of Y₃Al₂Ga₃O₁₂:Ce³⁺,Yb³⁺ Phosphors

et al. 2021

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“…Ca 2+ with a larger ionic radius is supposed to occupy the seven-coordinated Lu 3+ site and induce the stable Ce 4+ ions . In contrast, Li + ions are prone to occupy not only seven-coordinated Lu 3+ substitution sites but also the six-coordinated interstitial spaces. , The electrical neutrality of the system can be achieved by self-compensation between Li i and Li Lu and the variation in type and concentration of V O , rather than by the conversion of Ce valence states . Thus, it is reasonable to believe that Cu 2+ ions also tend to occupy the Lu 3+ substitutional site and the interstitial space.…”

Section: Results and Discussionmentioning

confidence: 99%

Czochralski Growth, Optical, Scintillation, and Defect Properties of Cu²⁺ Codoped Lu₂SiO₅:Ce³⁺ Single Crystals

Koschan

Foster

2019

Crystal Growth & Design

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Divalent cation codoping, such as with Ca 2+ and Mg 2+ , is beneficial for the scintillation performance enhancement of Czochralski-grown Lu 2 SiO 5 :Ce (LSO:Ce) single crystals for nuclear medical imaging applications, but with that benefit comes a tendency toward acentric growth due to the reduced surface tension of the melt. Here, we present a divalent Cu codoping strategy to achieve a simultaneous improvement of light yield, energy resolution, scintillation decay, and afterglow in LSO:Ce single crystals without destabilizing the solid−liquid interface or promoting acentric growth. High-quality 32-mm-diameter and 110mm-long LSO:Ce single crystals codoped with 0.1 and 0.3 atom % Cu 2+ ions in the melt were successfully grown using the Czochralski method. While the surface tension of the LSO melt does decrease with Cu 2+ codoping, analogous to the effect of Ca 2+ codoping, it is not reduced enough to affect the crystal growth stability or diameter control. With 0.1 atom % Cu 2+ codoping, the scintillation light yield of LSO:Ce can be significantly enhanced from 32 000 to 39 000 photons/MeV with an improved enegy resolution of 9% at 662 keV, and a reduced afterglow at room temperature. A continuous shortening of scintillation decay time with Cu 2+ codoping is ascribed to the combined effect of enhanced thermal ionization from the Ce 3+ 5d 1 state and a reduction of the emission contribution from Ce2 centers, i.e., in the site neighboring six oxygens. Thermoluminescence and afterglow measurements are utilized to study the defect structure and explain the variation in scintillation yield.

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“…We expect that such light yield enhancement in Ca 2+ codoped LSO:Ce single crystals can be attributed to the dissociation of spatially correlated Ce 3+ ions and oxygen vacancies. [50][51][52] The proposed hole auto-ionization process might be helpful to understand such effects.…”

Section: Thermal Quenching Modelmentioning

confidence: 99%

Ab initiostudy of luminescence in Ce-dopedLu2SiO5: The role of oxygen vacancies on emission color and thermal quenching behavior

Jia

Miglio

Mikami³

et al. 2018

Phys. Rev. Materials

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We study from first principles the luminescence of Lu2SiO5:Ce 3+ (LSO:Ce), a scintillator widely used in medical imaging applications, and establish the crucial role of oxygen vacancies (VO) in the generated spectrum. The excitation energy, emission energy and Stokes shift of its luminescent centers are simulated through a constrained density-functional theory method coupled with a ∆SCF analysis of total energies, and compared with experimental spectra. We show that the high-energy emission band comes from a single Ce-based luminescent center, while the large experimental spread of the low-energy emission band originates from a whole set of different Ce-VO complexes together with the other Ce-based luminescent center. Further, the luminescence thermal quenching behavior is analyzed. The 4f − 5d crossover mechanism is found to be very unlikely, with a large crossing energy barrier (E f d ) in the one-dimensional model. The alternative mechanism usually considered, namely the electron auto-ionization, is also shown to be unlikely. In this respect, we introduce a new methodology in which the time-consuming accurate computation of the band gap for such models is bypassed. We emphasize the usually overlooked role of the differing geometry relaxation in the excited neutral electronic state Ce 3+, * and in the ionized electronic state Ce 4+ . The results indicate that such electron auto-ionization cannot explain the thermal stability difference between the high-and low-energy emission bands. Finally, a hole auto-ionization process is proposed as a plausible alternative. With the already well-established excited state characterization methodology, the approach to color center identification and thermal quenching analysis proposed here can be applied to other luminescent materials in the presence of intrinsic defects.

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Effect of Li doping on the O vacancies in Lu2SiO5:Ce phosphors

Cited by 13 publications

References 15 publications

Effect of Oxygen Vacancies on the Persistent Luminescence of Y₃Al₂Ga₃O₁₂:Ce³⁺,Yb³⁺ Phosphors

Effect of Oxygen Vacancies on the Persistent Luminescence of Y₃Al₂Ga₃O₁₂:Ce³⁺,Yb³⁺ Phosphors

Czochralski Growth, Optical, Scintillation, and Defect Properties of Cu²⁺ Codoped Lu₂SiO₅:Ce³⁺ Single Crystals

Ab initiostudy of luminescence in Ce-dopedLu2SiO5: The role of oxygen vacancies on emission color and thermal quenching behavior

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Effect of Li doping on the O vacancies in Lu2SiO5:Ce phosphors

Cited by 13 publications

References 15 publications

Effect of Oxygen Vacancies on the Persistent Luminescence of Y3Al2Ga3O12:Ce3+,Yb3+ Phosphors

Effect of Oxygen Vacancies on the Persistent Luminescence of Y3Al2Ga3O12:Ce3+,Yb3+ Phosphors

Czochralski Growth, Optical, Scintillation, and Defect Properties of Cu2+ Codoped Lu2SiO5:Ce3+ Single Crystals

Ab initiostudy of luminescence in Ce-dopedLu2SiO5: The role of oxygen vacancies on emission color and thermal quenching behavior

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Effect of Oxygen Vacancies on the Persistent Luminescence of Y₃Al₂Ga₃O₁₂:Ce³⁺,Yb³⁺ Phosphors

Effect of Oxygen Vacancies on the Persistent Luminescence of Y₃Al₂Ga₃O₁₂:Ce³⁺,Yb³⁺ Phosphors

Czochralski Growth, Optical, Scintillation, and Defect Properties of Cu²⁺ Codoped Lu₂SiO₅:Ce³⁺ Single Crystals