White cathodoluminescence from Zn 0.3 Mg 0.7 Al 2 O 4 :Tb 3+ ,Eu 3+ . Shaat SKK 1,2 , Swart HC 1 and Ntwaeaborwa OM 1,* 1 Department of Physics, University of the Free State, Bloemfontein, ZA9300, South Africa. 2 Department of Physics, Islamic University, P. O. Box 108, Gaza, Palestine. * Corresponding author: ntwaeab@ufs.ac.za Abstract. In this study, white cathodoluminescence (CL) was generated from Zn 0.3 Mg 0.7 Al 2 O 4 :Tb 3+ ;Eu 3+ prepared by the combustion route using urea as a fuel metal and nitrates as precursors. The X-ray diffraction (XRD) patterns from the samples showed phases associated with cubic structures of ZnAl 2 O 4 and MgAl 2 O 4 . The particle morphology of the Zn 0.3 Mg 0.7 Al 2 O 4 :Tb 3+ ;Eu 3+ showed different irregular shapes. White CL with the CIE coordinates (x = 0.343, y = 0.323) was observed when the phosphor was excited by a low voltage (2 keV) electron beam in vacuum. This was a result of the simultaneous emission of blue and green emissions from Tb 3+ , and red emission from Eu 3+ . This phosphor is evaluated for possible applications in white LEDs. . 1. Introduction Nowadays, researchers are working to prepare, and develop white light emitting phosphors that can be used in solid state lighting applications such as flat panel displays (FPD), phosphor lamps and light emitting diodes (LEDs). The white colour is the combination of the primary colours namely blue, green and red. It is, however, not easy to have one phosphor to emit these three colours simultaneously. Traditionally, the production of white light in LEDs can be achieved by two routes. These are by combining yellow phosphor such as YAG:Ce 3+ with a lnGaN-based blue diode and by combining a UV chip with a three converter system of red, green, and blue phosphors. The problems with these are poor rendition and high thermal quenching of the yellow phosphor and reabsorption of the blue emission by the red or green phosphor in the three converter system [1]. To overcome these problems, a new generation of single host phosphors prepared mostly by doping alkali earth aluminates with divalent alkali earth and/or trivalent rare-earth ions has been developed. Alkali earth aluminates are chemically stable, environmentally friendly [2], and they can be easily produced cost- effectively. For example, a white emission from a tunable Mg 3 Al 2 O 5 Cl 2 :Ce 3+ ,Eu 2+ phosphor based on energy transfer from Ce 3+ to Eu 2+ by a down-conversion process was reported by Song et al [1], while Shaat et al [3] generated white light from Ca x Sr (1-x) Al 2 O 4 :Tb 3+ ;Eu 3+ phosphor. In this study the combustion method was used to prepare Zn 0.3 Mg 0.7 Al 2 O 4 :Tb 3+ ,Eu 3+ to produce white cathodoluminescence. The structure, morphology and cathodoluminescent (CL) properties of the prepared phosphor were examined, and are reported. 2. Experimental 2.1 Sample Preparation A combustion method was used to prepare Tb 3+ and Eu 3+ co-doped Zn 0.3 Mg 0.7 Al 2 O 4 nanophosphor. The metal nitrates of Zn(NO 3 ) 2 .4H 2 O, Mg(NO 3 ) 2 .6H 2 O, Al(NO 3 ) 3 .9H 2 O, Tb(NO 3 ) 3 .6H 2 O, Eu(NO 3 ) 3 .5H 2 O, and urea CON 2 H 4 of AR grade purchased from Merck, South Africa were used as starting materials (precursors), and were used as obtained without further purification. Distilled water was used to dissolve the precursors with vigorous stirring at 50°C for 0.3 hr until the solution became clear. The resulting solution was transferred to a muffle furnace maintained at 450 ± 10% o C. The brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Institutional Repository of the Islamic University of Gaza