ZnO nanophosphor Co doped with Ce, Eu and Tb

摘要

ZnO nanophosphor co-doped with Ce, Eu and Tb [Zn_(1-x-y-z)O:Ce_xEu_yTb_z (x, y and z = 0.1, 0.5, and 1.0 mol.%)] was prepared by the co-precipitation method followed by sintering in the air at 700 °C. The powder XRD spectrum could be indexed using the JCPDC File No. 36-1451 implying that the doping levels investigated in the present study did not change the basic wurtzite crystal structure of the ZnO. The absence of any independent phases of the Ce, Eu and Tb confirmed the incorporation of these dopants in the ZnO lattice. The dopants could enter the ZnO lattice interstitially or/and substitutional. The substitutional incorporation could result in the development of strain in the unit cell as the radii of all the dopants are greater than Zn. This strain could be responsible for the observed shift in the peak positions of diffraction peaks; the observed shift was ～0.20° (towards the lower side) for the diffraction peak with (hkl) value (101) for ZnO doped with 0.5 mol.% Ce, Eu and Tb. On the other hand, interstitial substitution could result in the creation of the defects like vacancies. These defects could create the inter-band defect states which could emit in the visible region (400-700 nm).Emission in the visible region was observed when excited with the 280,300 and 380 nm radiation from a Xe lamp; the 280 and 300 nm excitations resulted in broad emission centered around ～510 nm while relatively sharp emission peaks were observed with 380 nm radiation; the emission intensity was found to be dependent on the dopant concentration. The chromaticity color coordinates (x and y) of the observed broad emission were calculated using the data from the emission spectrum. The best calculated values were: ⅹ = 0.33 and y = 0.34 for ZnO co-doped with Ce 0.5, Eu 0.1 and Tb 0.1 mol.%; these "x and y" values being very close to those of the "sunlight at noon" (x = 0.33 and y = 0.33), indicate the potential of this material for the realization of the white light sources.