Strategy to achieve the emission of white light and other colors from ZnAl 2 O 4 : (Eu 3+ + Tb 3+ ) films deposited by the USP technique

Zinc aluminate films doped and co-doped with trivalent terbium and europium ions were deposited by ultrasonic spray pyrolysis technique (USP). Photo and cathodoluminescent characteristics of these films were studied as a function of the doping concentrations. Results showed that crystalline structure of ZnAl2O4 and ZnAl2O4: (Tb3+  + Eu3+) films, deposited at 550 °C, turns out to be cubic, which is typical of the zinc aluminate ("gahnite"). The white light emission from ZnAl2O4: (Tb3+  + Eu3+) films was a consequence of the optical response of the Tb3+ and Eu3+ ions and the intrinsic emission of the host lattice. Green emission was related with Tb3+ ions; red emission with Eu3+ ions and the violet-blue emission was associated with the un-doped ZnAl2O4. The light emission from ZnAl2O4: (Tb3+  + Eu3+) films was tuned as a function of the relative doping concentration (Tb3+ and Eu3+ ions) and the excitation wavelength; the CIE chromatic coordinates for the best sample were (0.3364, 0.3305). In this way, the emissions of several colors such as blue, green, red, yellow, orange and mainly white were obtained. The characteristics of the surface morphology and the chemical composition of the films studied are also shown.