DSpace at VNU: Synthesis and optical properties of ZnAl2O4:Cr 3+, Tb3+ powders

spectra excited by 528 nm
wavelength of ZnAl2−x−y Tbx Cry O4 samples with various
x and y, annealed at 1100 ◦ C. It can be seen from Figure 8a that at the high Cr3+ concentrations (y = 0.050,
0.100) the intensity of the lines at 667, 675, 686, 698,
708 and 717 nm considerably reduces. Meanwhile, some
new lines at 707, 732 739 and 746 nm appear. After references [5–7], at the high Cr3+ concentrations the Cr3+ Cr3+ pairs are expected to form, and the line at 707 nm
is originated from the nearest Cr3+ -Cr3+ pairs. By examining PLE spectrum, the lines at the wavelengths of 732,
739 and 746 nm are believed to be the phonon-sidebands
of the line at 707 nm (the PLE spectra not shown here).
Figure 8b shows the PL spectra of ZnAl2−x−y Tbx Cry O4 samples, annealed at 1100 ◦ C, with y = 0.005 and
various x, excited by the wavelength of 528 nm. As seen
from the figure, with increasing the Tb3+ ion concentration up to x = 0.050, 0.100, the shape of the spectra does
not change, but their intensity is decreased. Therefore by
selecting the appropriate mole fractions x and y, we can
obtain the materials strongly emitting in both blue-green
and red regions.

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T.T. Loan et al.: Synthesis and optical properties of ZnAl2 O4 :Cr3+ ,Tb3+ powders

4 Conclusion

(a)

The ZnAl2 O4 spinel powders co-doped with Tb3+ and
Cr3+ ions have been successfully synthesized by a solgel technique. The samples undergone heat-treatment at
1100 ◦ C exhibited the best crystallinity. The PL spectra of the samples showed two emission regions: the first
(blue-green) one was related to the emission of Tb3+ ions
and the second (red) one was related to the emission of

Cr3+ ions. By selecting the appropriate mole fractions
of the Tb3+ ions x and Cr3+ ions y, we can obtain the
materials strongly emitting in both blue-green and red
regions.

(b)

This work is financially supported by VNU University of
Science (Project No. NT-12-10) and Ministry of Science and
Technology of Vietnam (Project No. 103.02.51.09 from
NAFOSTED).

References

Fig. 8. The PL spectra excited by the wavelength of 528 nm
of the ZnAl2−x−y Tbx Cry O4 samples, heat-treated at 1100 ◦ C
(a) with x = 0.005 and different y, and (b) with different x and
y = 0.005.

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