Wydział Chemii

Anna Dobrowolska

Eugeniusz Zych

2012

Journal of Physical Chemistry C

116

25493-25503

10.1021/jp306764f

Naukowa

Angielski

Artykuł

Ca₃Y₂Si₃O₁₂ powders activated with Eu (0.1–25%) were prepared by means of ceramic method. Their spectroscopic properties in VUV-UV–vis region were investigated. Luminescence measurements indicated that Ca₃Y₂Si₃O₁₂ prepared in a strongly reducing atmosphere of 20%N₂–80%H₂ mixture contained both Eu²⁺ and Eu³⁺ ions, and both were able to generate their characteristic emissions. A superposition of the broad band luminescence of Eu²⁺ and narrower 4f → 4f luminescent features of Eu³⁺ upon excitation with 395 nm light-emitting diode covered almost the whole visible part of spectrum. The ratio between Eu²⁺ and Eu³⁺ emissions was reproducible, and, with increasing content of Eu, the relative intensity of the red component from Eu³⁺ became systematically stronger. The Eu²⁺ luminescence in Ca₃Y₂Si₃O₁₂ was characterized by an extraordinary large Stokes shift of ∼8960 cm^–1 and most probably had an anomalous character with a defect, presumably O-vacancy located in the vicinity of Eu²⁺, being involved in the emission generation. Excitation into the VUV-UV region with synchrotron radiation revealed that at 10 K, despite Eu³⁺ and Eu²⁺ ions, two kinds of intrinsic emissions, peaking around 340 and 420–440 nm, contributed to the luminescence of Ca₃Y₂Si₃O₁₂:Eu. Luminescence measurements in the range of 293–573 K and decay kinetics of Eu³⁺ and Eu²⁺ emissions revealed that the continuously decreasing fraction of Eu²⁺ ions contributed to the emission with increasing temperature, yet the thermal quenching of emission monitored by changes in its decay time could merely be seen above 500 K. The unusual temperature behavior of Eu²⁺ luminescence in Ca₃Y₂Si₃O₁₂:Eu²⁺,Eu³⁺ was assigned to the instability of exciton-like state diffused over [Eu²⁺-O_vac] defect cluster involved in the luminescence of Eu²⁺. Although the performance of the phosphor was not optimized, 40–44% of the quantum efficiency of the overall luminescence upon near-UV excitation was measured, proving its high potential.

https://doi.org/10.1021/jp306764f

https://www.acs.org/content/acs/en.html