Fabrication of submicron-sized oxide phosphors and their spectroscopic properties

Abstract

In our report we will present a few synthesis techniques, which may be routinely used to fabricate nanoparticulate or submicron-sized powder phosphor materials. We will focus on procedures, which may be easily scalable and which allow making powders of low agglomeration or aggregation and which are energy-efficient.Among others we will report on making powders of garnets, YAG:Pr, YAG:Eu, LuAG:Pr by means of molten salts technique giving particles of almost spherical shape and sizes in the range of 200-500 nm, as seen in Figure 1. What is the most special in the case of this fabrication technique is an extremely low temperature necessary to convert a stoichiometric mixture of the metal nitrates into crystalline garnets. The process may be effectively performed below 400 °C even. However, the best results may be obtained carrying out the synthesis around 500 °C. The classical ceramic synthesis requires temperatures in the range of 1500-1700 °C. To the best of our knowledge, only pressure-assisted synthesis techniques allow to reduce the temperatures of the process to a few hundred centigrade.We will also present synthesis method based on homogeneous precipitation of solids from water solutions with or without the use of surfactants. We will discuss the influence of SO 4 2-ions addition on the properties of the final products, especially on particles agglomeration. We shall discuss the applicability of these preparation techniques to fabrication of powders for X-ray detection.The description of the various fabrication methods will be associated with presentation of the powders X-ray diffraction analysis and TEM/SEM images.These will prove the nonagglomerated microstructure and crystalline character of the products.A part of the talk we will devote to present some spectroscopic results characterizing the luminescent properties of some of the products. Among others we shall discuss results of experiments performed with the use of synchrotron radiation (Hasylab, Superlumi Station in Hamburg).

Recent progress in low-voltage cathodoluminescent materials: synthesis, improvement and emission properties

“…In addition, the resolution is a pivotal index for display quality, which is also closely related to the particle size of the luminescent materials. 102 Although some theoretical and experimental considerations have suggested that the most efficient phosphors are spherical and submicron grain sized, 103,104 This journal is © The Royal Society of Chemistry 2014 nanoparticle phosphors might be more appropriate for lowvoltage FED applications in terms of the following aspects: 15,27,101 (1) in some cases, the preparation of nanocrystalline phosphors requires much less temperature and time in comparison with conventional microsized grains, which lower the synthesis cost;…”

Luminescence properties of Y3Al5O12:Ce nanoceramics

“…[5,20] for details) and was used as initial charge for the preparation of transparent YAG:Ce OC. The nanopowder was pressed into yellow ceramic tablets.…”

“…Transparent optical ceramics (OC) of Y 3 Al 5 O 12 (YAG) garnet doped with rare-earth ions is now being considered as an alternative to bulk single crystals (SC) of these materials for laser media applications and scintillators [1][2][3][4][5]. Usually OC are obtained from initial row powders with small grain size [1,2] or from sintered YAG-based nanopowders [3,4] previously prepared by sol-gel methods [4][5][6].…”

“…Usually OC are obtained from initial row powders with small grain size [1,2] or from sintered YAG-based nanopowders [3,4] previously prepared by sol-gel methods [4][5][6]. The main differences of the properties of YAG-based OC in comparison with SC can be the relatively lower temperature of preparation of OC (about 1700-1750 1C) [1][2][3][4][5][6] than that for YAG:Ce SC obtained by melting at high (1970 1C) temperature by the Czochralski or modified Bridgman methods [7]. Therefore, OC can possess, in principle, lower concentration of Y Al antisite defects (AD), which are typical for melt-grown YAG-based SC [7][8][9][10][11].…”

On the synthesis of LuAG:Ce fine powders by molten salts methods and spectroscopic properties of the products

“…The synthesis is based on the molten salts method, which we previously successfully applied for making YAG:Ce [8]. The structure and morphology of the products synthesized with two different compositions of the molten salts will be analyzed by an X-ray powder diffraction and scanning electron microscopy.…”