Effect of Particle Size on the Luminescent Properties of Europium Doped Yttrium Oxide Nano-Phosphors
- PDF / 55,267 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 67 Downloads / 282 Views
Effect of Particle Size on the Luminescent Properties of Europium Doped Yttrium Oxide Nano-Phosphors Thomas S. Copeland, Burtrand I. Lee, and Amanda K. Elrod School of Materials Science & Engineering, Clemson Univ. Clemson, SC 29634 USA ABSTRACT Red light emitting Eu3+ doped Y2O3 phosphor nano-particles were synthesized by a solgel method combined with a furnace firing. The particle size, measured using dynamic light scattering (DLS), was between 36nm and 1 micron depending on the conditions. Final dopant concentrations were measured through inductively coupled plasma (ICP). The ICP results show a dopant loss of 58% during the processing for the europium doped yttria. Red photoluminescence (PL) and cathodoluminescence (CL), at 614nm was observed from the phosphor particles under UV excitation and electron bombardment. Results show that the samples with a mean diameter of 30nm displayed a significant increase in PL brightness over the samples whose mean diameter was 215nm. The lag in PL, and CL intensity behind the commercial reference samples is attributed to the significantly lower dopant levels present in the experimental phosphors. Results also indicate that these processing methods and nanophosphors may be a useful alternative to current materials and methods. INTRODUCTION Yttrium oxide doped with trivalent europium (Y2O3:Eu3+) is a common phosphor in cathode ray tubes and field emission displays (FEDs) and is an attractive alternative to sulfide phosphors. These phosphors, prepared with sub-micron particle sizes, may offer additional improvements for several reasons. Yoo, et al [1] predicted that as the particle size decreased, so would the optimum CL work voltage. The decrease in phosphor particle size will also result in a higher number of particles per unit volume and increase the possibility of electron penetration to the dopant site. Additionally, a smaller phosphor size could result in a smaller screen pixel size and a higher degree of transparency for phosphors dispersed in other substances. Concerns have been raised about the effect of particle size on optimal doping levels. Zhang, et al. [2] studied the effect of decreasing particle size on optimum doping concentration in the Y2SiO5:Eu3+ system. Suppression of concentration quenching with respect to luminescent intensity was observed in the nano-sized samples. Zhang, et al. [2] were able to triple the amount of dopant added in the nano-particle sample over the bulk micron sample before the phosphor displayed negative affects. At this higher mole fraction of europium, the luminescent intensity of the nano-phosphors was twice as large as that observed from the micrometer scale sample at its corresponding maximum doping level. There are other thoughts on why the luminescence of different phosphor systems is enhanced by the reduction of particle size. One such theory is the Purcell Effect. This concept, first proposed over 50 years ago, is now well established thanks to experimental and theoretical work in the field of cavity quantum electrodynamics [3]. T
Data Loading...
