Preparation and Characterization of Fine‐Grain Yttrium‐Based Phosphors by Sol‐Gel Process

Abstract

The preparation, characterization, and luminescence of yttrium-based phosphors such as europium activated yttrium oxide (red) and terbium activated yttrium aluminate (green) by sol-gel processes is presented. The sols of yttrium hydroxide were synthesized by various routes. It was found that the sols obtained through an ion exchange column were pure and without any cross contamination. The aluminum hydroxide sols were prepared from aluminum chloride and ammonium hydroxide. A number of gel samples were synthesized by mixing stoichiometric amounts of Y(OH)3 and Al(OH)3 to obtain Y3A15012, Y4A1209, and YAIO3 with trace amounts of rare earth, RE(OH)3 gels as activators. These gels were dried at 30 to 80°C. From the thermal analyses, all possible temperature transitions were identified. After calcination with different temperatures and durations, these phosphor powder samples were characterized for crystallization, spectral energy distribution, and morphology. The samples synthesized at lower temperatures (< 1000°C) were fully crystallized. The average particle size of these phosphors was in the range of 1 to 2 p.m. From the luminescence spectral data, all possible transitions 5D0 -7F12 corresponding to Eu3 in Y203, and 5D4 -* 7F1 6 corresponding to (Th3 ) in yttriumaluminum-garnet (YAG) matrices were identified. The luminescent efficiencies of these phosphors were comparable with commercially available phosphors having larger particles (6 to 10 p.m). The preparation of other yttrium-based phosphors such as YAG:RE3 and Y2SiO5:RE3 (RE = Tm, Ce, Th, and Eu) and the luminescence studies of these materials at low voltages for field emission display applications are in progress.

Síntesis de nuevos pigmentos cerámicos de color rojo mediante el método de Pechini

“…Un ejemplo de ello es su aplicación en el campo de la óptica y el tradicional desarrollo de láseres y fósforos en esta estructura (11,12,13,14).…”

Influence of Bi3+content on photoluminescence of InNbO4:Eu3+,Bi3+for white light-emitting diodes

“…2. The particles have a narrow size distribution and the median diameter is about 2.3 µm, which elucidates why the phosphors are meeting the production requirements of solid lighting facilities [30]. (CT) [31], the other is a narrow peak region above 362 nm which is assigned to the 4f 7 configuration transitions of Eu 3+ from the ground state to the excited state in the host lattice [32].…”

Nanorods of white light emitting Sr2SiO4:Eu2+: microemulsion-based synthesis, EPR, photoluminescence, and thermoluminescence studies

“…However, by this novel reverse micellar route, we could bring down the temperature required for the formation of single-phase Sr 2 SiO 4 to as low as 600 C. Figure 3 shows the typical SEM image of Sr 1.99 Eu 0.01 SiO 4 phosphor, and it is clearly observed that the particles have a mixed morphology of agglomerated particles with some of them showing rod-like morphology with the diameter of about 100 nm and the length of 0.5-1 mm, which makes the phosphor have high surface area. It is found that the phosphors with higher surface area have better thermal conductivity when excited with highenergy photons [22] and are favourable to the lifetime of ultraviolet GaN-based w-LED. Based on the morphological characterisation, a mechanism is proposed for the formation of Sr 1.99 Eu 0.01 SiO 4 nanorods and can be seen from Figure 4.…”