|
|||||
|
|
Optical characterization of fourfold (Td)- and sixfold (Oh)-transition-metal species in MgAl2O4:Co by time-resolved spectroscopy |
|
| Authors: | L. Nataf,F. Rodrí guez,V. Ulanov |
| Affiliation: | a DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander, Spain b Department Física Aplicada, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander, Spain c Russian Academy of Sciences, Sibirski Trakt 10/7, 420029 Kazan, Russia |
| Abstract: | This work investigates the origin of novel visible photoluminescence (PL) bands observed in the spinel MgAl2O4:Co2+. Besides the well-known fourfold-coordinated Co2+(Td) PL at 670 nm [N.V. Kuleshov, V.P. Mikhailov, V.G. Scherbitsky, P.V. Prokoshin and K.V. Yumashev, J. Lumin. 55 (1993) 265.], a rich structured PL band at 686 nm was also observed that we associate with uncontrolled impurities of sixfold coordinated Cr3+(Oh) by time-resolved spectroscopy and lifetime measurements and their variation with temperature. We also show that the lifetime of the Co2+(Td) emission at 670 nm varies from τ=6.7 μs to 780 ns on passing from T=10 to 290 K. This unexpected behaviour for Td systems is related to the excited-state crossover (4T1↔2E), making the emission band to transform from a narrow-like emission from 2E at low temperature to a broad structureless band from 4T1 at room temperature. |
| Keywords: | Co2+ Cr3+ MgAl2O4 Crystal field Lifetime Excited state crossover |
| 本文献已被 ScienceDirect 等数据库收录！ | |