The ZnGa2 O 4 Phosphor for Low‐Voltage Blue Cathodoluminescence

Abstract

The ZnGa204 phosphor has been investigated for its application to vacuum fluorescent displays (VFDs) utilizing lowvoltage cathodoluminescence. It is expected that this oxide phosphor does not cause damage to filaments in VFD's, while it is a serious problem for conventional sulfide phosphors. This phosphor shows blue luminescence with a spectral peak at 470 nm and a chromaticity at X = 0.170 and Y = 0.130. A luminous efficiency of 0.7 lm/W has been obtalned, when the VFD with this phosphor is operated at 30 V dc. The results of high-temperature operating life test have proven the excellent stability of VFDs utilizing this phosphor.Presently, sulfide phosphors are extensively used for vacuum fluorescent displays (VFDs). However, as previously discussed by the authors (1), sulfide phosphors emit sulfide gases and decompose to scatter phosphor material during electron excitation. This causes not only the decrease of luminous efficiency of the phosphors but also the deterioration of cathode filament, which are serious problems in multicolor VFDs.An attempt has been made to study the ZnGa204 powder phosphor to be used as the alternative of blue cathodoluminescent phosphor of ZnS:C1 phosphor. The ZnGa204 phosphor is a compound oxide of ZnO and Ga20~, crystallizing in the spinel structure, and its optical bandgap is about 4.4 eV. ZnGa204 shows emission from green to red when it is doped with Cr and Mn, and also shows blue emission even without being doped with impurity. It is well known that the phosphor is excited by electronbeams followed by energy transfer to the luminescent center to emit light. Therefore, the essential requirements for low-voltage cathodoluminescent (LCL) phosphors are low resistance and low threshold voltage, as well as excellent crystallinity. In view of these requirements, the ZnGa204 phosphor, which is inherently low in conductivity, was added with conductive materials. This paper mainly discusses the luminous characteristics of the phosphor which was applied to the VFD. REFERENCE

Formation of Eu2O3 Nanorods through Solvothermal Routes by Surfactant Assistance

“…Eu 2 O(CO 3 ) 2 •H 2 O nanorods are 80-140 nm in diameter and 1.5-5 µm in length and in comparison Eu(OH) 3 nanorods are 15-100 nm in diameter and 150-550 nm in length. 7 When it was calcined, the Eu 2 O(CO 3 ) 2 •H 2 O nanorod was decomposed with results that the granule-rod occurred. Figure 3 illustrates the role of the surfactant SDS playing in the synthetic routes.…”

“…Figure 3 illustrates the role of the surfactant SDS playing in the synthetic routes. The images of the Eu 2 O(CO 3 ) 2 •H 2 O samples by field-emission scanning electron microscopy are shown in Figure 3. The shape of the synthetic products without surfactant SDS (in Figure 3a) reveals that a part of rods and a lot of irregular flakes are formed.…”

“…This route is simple and can be easily controlled. The semifinished product Eu 2 O(CO 3 ) 2 • H 2 O nanorod is monocrystalline and Eu 2 O 3 nanorod comprises Eu 2 O 3 nanoparticles which are monocrystalline too.…”

Luminescence properties of ZnGa2O4 and ZnAl2O4 spinels doped with Eu3+ and Tb3+ ions

“…ZnGa 2 O 4 and ZnAla 2 O 4 phosphors have gained much attention for use in field emission displays (FEDs) and vacuum florescent displays (VFDs) [1,2] because they exhibit higher chemical stability than commonly used sulfide phosphors. Since ZnGa 2 O 4 and ZnAla 2 O 4 are oxide based phosphors, many of the degradation problems associated with sulfide-based phosphors are avoided.…”

Direct Precipitation of Spinel-Type Zn(Fe, Ga)2O4 Solid Solutions from Aqueous Solutions at 90°C: Influence of Iron Valence of Starting Salt on Their Crystallite Growth

“…ZnGa 2 O 4 with spinel-type structure is UV-transparent and electroconductive so that it has a possibility to be utilized for UV-photoelectronic devices as one of the new transparent and conductive materials (1)(2)(3), as well as a good low-voltage phosphor material used in a new kind of vacuum flat cathode ray tube of the field emission display (4). Synthesis of reactive fine powders of ZnGa 2 O 4 spinel through chemical solution routes, i.e., glycothermal synthesis at 3001C (5) and hydrothermal synthesis below 2401C (6)(7)(8) have been reported.…”