Defect level influenced optical properties of Eu3+ and Tb3+ doped in ZnO-CaAlxOy composite

A Eu3+/Tb3+ doped composite material (calcium aluminate zinc oxide) has been synthesized by the combustion process. The formation of the composite has been verified by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Fourier transform infrared (FTIR) spectroscopy has been used to investigate the vibrations of the bands in of the material. The luminescence of the undoped composite material shows the band edge emission due to ZnO (lambda(exc) = 355 nm) in the UV/blue and defect level emissions in the green and red. The band edge emission shows a shift toward shorter wavelength and the effect of an optical avalanche intensity when temperature is lowered (50-30 K). No effect on the defect emissions is seen. Intense fluorescence due to transitions D-5(J) (J = 0, 1, and 2) to the lower levels F-7(J) (J = 0, 1, 2, 3, 4, 5 and 6) is seen. The large intensity is attributed to contribution from the defect emission from ZnO. The same material doped with Tb3+ instead of Eu3+ shows that the presence or absence of ZnO has little effect. (C) 2012 Elsevier B.V. All rights reserved.