Colour tuning and energy transfer pathways in MgAl 2 O 4 triply doped with 0.1% Ce 3+ , 0.1% Eu 2+ , x% Tb 3+(0⩽x⩽2%)

The effects of varying the Eu3+ concentration on the structural and optical properties of Mg1.5Al2O4.5:x% Eu3+ (0 ≤ x ≤ 2) nanophosphors prepared by sol–gel method

“…The infrared spectroscopy (IR) spectra showed the presence of the bands around 700 and 520 cm À1 , which correspond to the AlO 6 groups building up the MgAl 2 O 4 spinel. The Eu 3þ ion was partially reduced to the divalent (Eu 2þ ) state at the annealing temperature of 700 C and 800 C. This possibility of reduction of Eu 3þ to Eu 2þ at this temperature has recently been confirmed by Motloung et al 9 on the triply doped MgAl 2 O 4 system. The PL results revealed the existence of the energy transfer from Eu 2þ !…”

“…The PL results showed that the photoexcitation of the F (277 nm) and F + (342 nm) centres caused the radiative relaxation channel with the emission peaks located at 388 and 560 nm, which were, respectively, attributed to defect centres located at different levels. This host material has also been doubly doped 8 and recently triply doped 9 with other REs and TMs. 4,8 Brito et al 8 have presented co-doped MgAl 2 O 4 with Eu 3+ , Dy 3+ .…”

STRUCTURAL AND PHOTOLUMINESCENCE CHARACTERIZATION OF MgAl2O4:Eu PHOSPHOR SYNTHESIZED BY COMBUSTION METHOD.

“…Eu materials prepared at 500 0 C were recorded under emission monitored at 440 nm. The excitation spectra display intense peaks at 275 nm would be due to the defects within the host material [5].…”

“…On excitation with UV, two types of lowest excited states are possible, namely 6 P j (f-f) or 4f 6 5d (f-f), depending on the host matrix [13]. In case of Eu 2+ ion in MgAl 2 O 4 the possible lowest excited states is 4f 6 5d (f-f) [5]. The optical band gap energy value of magnesium aluminate is estimated as 4.5 eV [14].…”

“…Inorganic phosphors doped with rare earth ions have been used in lighting systems and for multicolor displays to overcome the drawback such as poor color rendition, high toxicity and complicated synthesizing process [3,4]. Among them, magnesium-aluminum oxide (MgAl 2 O 4 ) spinel crystals have received a great deal of attention due to its mechanical strength, high resistance to chemical attacks, and its outstanding dielectric and optical properties [5] ) and it was characterized by using techniques such as powder X-ray diffraction (XRD), and photoluminescence (PL).…”