Photoluminescence and cathodoluminescence properties of Li<sup>+</sup> doped Gd<sub>1.88</sub>Eu<sub>0.12</sub>O<sub>3</sub>

Abstract

Li+-doped cubic Gd1.88Eu0.12O3 phosphors were synthesized at 1200 degrees C in air by co-precipitation (CP) and solid state reaction (SS) methods. X-ray diffraction analysis revealed that, regardless of synthetic method, the average crystallite size for Li+-free Gd1.88Eu0.12O3 was approximately 400 nm, then increased with the amount of Li+ and at 20 mol%, reached about 2.3 mu m. Under excitation of the charge transfer band of Eu3+ at 245 nm, Gd1.88Eu0.12O3 exhibited a dominant photoluminescence (PL) red emission peak at 611 nm assigned to the electric dipole transition D-5(0) -> F-7(2) of Eu3+. The red emission peak intensity increased consistently with the amount of Li+-doping, while CP method was found to be effective in improving the red emission intensity at lower amounts of L-i+-doping from 0 to 8 mol%. Cathodoluminescence (CL) property was studied by mounting the synthesized phosphor on a vacuum fluorescent display (VFD) operated at an anode voltage of 50V. The Gd1.88Eu0.12O3 exhibited a similar spectrum with an intense red emission peak at 611 nm, and the highest luminance intensity for the CL red emission was achieved for 8 mol% Li+-doped Gd1.88Eu0.12O3 synthesized by SS method. The evaluation results of PL and CL properties suggested that, besides the crystallite size of Gd1.88Eu0.12O3, dispersion property of Eu3+ ions in the host Gd2O3 was an important factor for improving luminescent properties of Gd1.88Eu0.12O3. Moreover, under the present VFD operating condition at the low excitation voltage, it was thought to be essential for improving CL emission intensity to maintain a sufficient surface area of Gd1.88Eu0.12O3. (C)2015 The Ceramic Society of Japan. All rights reserved.