Paul J. Marsh

The investigation of cubic spherical submicron particles of non-doped Y₂O₃and Y₂O₃doped with Eu³⁺in a TEM using CL from individual particles is described.

Abstract— The current status of AC powder electroluminescent (ACPEL) displays is reviewed with particular emphasis given to color and lifetime. The printing of the displays in forward and reverse architectures is also discussed, in addition to the fabrication of ACPEL displays with interdigitated electrodes, and different types of ACPEL phosphors and materials for back electrodes, transparent conducting electrodes, binders, and dielectrics are considered. Furthermore, shape conformable and highly flexible ACPEL displays are surveyed.

Despite many researches over the last half century, the mechanism of ac powder electroluminescence remains to be fully elucidated and, to this end, a better understanding of the relatively complex structure of alternate current electroluminescence (ACEL) phosphors is required. Consequently, the structure and morphology of ZnS:Cu,Cl phosphor powders have been investigated herein by means of scanning electron microscopy (SEM) on hydrochloric acid-etched samples and X-ray powder diffraction. The latter technique confirmed that, as a result of two-stage firing during their synthesis, the phosphors were converted from the high temperature hexagonal (wurtzite) structure to the low temperature cubic (sphalerite) polymorph having a high density of planar stacking faults. Optical microscopy revealed that the crystal habit of the phosphor had the appearance of the hexagonal polymorph, which can be explained by the sphalerite pseudomorphing of the earlier wurtzite after undergoing the hexagonal to cubic phase transformation during the synthesis. SEM micrographs of the hydrochloric-etched phosphor particles revealed etch pits, a high density of planar stacking faults along the cubic [111] axis, and the pyramids on the (111) face. These observations were consistent with unidirectional crystal growth originating from the face showing the pyramids.

Novel, flexible ACEL lamps have been developed for innovative display applications. These lamps contain a single emissive layer comprising of ACEL phosphor, a binder, ferroelectric nanoparticles and optional dye. This architecture reduces fabrication costs and enables high luminances (ca. 200 cd/m ² ) to be achieved at 110 V and 400 Hz.

We report flexible, multi‐colored electroluminescent displays that are produced using offset lithographic printing of interdigitated electrodes. These displays can be mass produced at low cost as they require no transparent conducting oxides as anode. Applications include back‐lighting, large‐scale low‐cost lighting displays, and low‐resolution display technology.

An oxide/oxysulfide based phosphor triad with particle sizes of around 1micrometer (green Y ₂ SiO ₅ :Tb or Y ₂ O ₂ S:Tb, and blue Y ₂ SiO ₅ :Ce) down to 250nm for the red Y ₂ O ₃ : Eu is reported. These phosphors perform well in brightness under the conditions necessary for use in FED's and are of suitable size for use in high definition screens. We also report a green emitting Y ₂ O ₂ S:Tb phosphor that has been prepared by a new method involving homogeneous precipitation of the precursors and a new firing regime. The resulting cathodoluminescent phosphor having submicrometer size particles has a luminous efficiency of 34.6 lm/W at an electron beam accelerating voltage of 5000 V.

The syntheses of MGa2S4MGa2S4 (where M=Ca,M=Ca, Sr, and Zn), CuMS2CuMS2 (where M=InM=In or Cr), Ba2ZnS3,Ba2ZnS3, and CuInSe2CuInSe2 by utilizing sulfur or selenium solutions in hydrazine monohydrate are reported. Scanning electron microscope studies of the morphology of the resulting materials prepared by this route are presented. The photoluminescence spectra of the phosphors SrGa2S4:Eu.SrGa2S4:Eu. SrGa2S4:Ce,SrGa2S4:Ce, ZnGa2S4:Mn,ZnGa2S4:Mn, CaGa2S4:Eu,CaGa2S4:Eu, and Ba2ZnS3:MnBa2ZnS3:Mn are displayed. The method is more environmentally friendly than traditional preparations (very little sulfur-based gases are formed). Additionally, it is a simple and rapid preparation, producing a good yield. The procedure facilitates the formation of ternary metal sulfides or selenides. It is further shown that for optimum performance of SrGa2S4:Eu,SrGa2S4:Eu, the phosphor needs to be fired in a reducing atmosphere to convert all of the Eu3+Eu3+ to Eu2+.Eu2+. © 2001 The Electrochemical Society. All rights reserved.