Some features of white-emitting phosphors for cathodoluminescence light sources
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OZOL, Dmitry. Some features of white-emitting phosphors for cathodoluminescence light sources. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 121.
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Materials Science and Condensed Matter Physics
Editia 7, 2014
Conferința "Materials Science and Condensed Matter Physics"
7, Chișinău, Moldova, 16-19 septembrie 2014

Some features of white-emitting phosphors for cathodoluminescence light sources


Pag. 121-121

Ozol Dmitry
 
Moscow Institute of Physics and Technology
 
Disponibil în IBN: 4 martie 2019


Rezumat

The selection of white-emitting cathodoluminophores with the maximal luminous efficiency (lm/W) attracts interest owing to the development of cathodoluminescent light sources - general purpose field emission lamps. A range of white phosphors used in black-and-white television tubes is known. The following sufficiently effective phosphors have been most widely used [1-3]: 1. ZnS:Ag + (Zn,Cd)S:Cu,Al; 2. ZnS:Ag + (Zn,Cd)S:Ag; 3. ZnS:Ag + ZnS:Cu,Al + Y2O2S:Eu3+; 4. (Zn,Cd)S:Ag,Au,Al; 5. Y2O2S:Tb and the similar a rather more effectiveY2O2S:Tb,Dy. The first three compositions are mixtures of luminophores - mixtures allow one to obtain the higher energy efficiency owing to the lowering of Stokes losses by selection of the appropriate forbidden gap width for each emission color separately. The phosphors 4 and 5 contain only one component; their efficiency is lower than for the phosphor mixtures, and they have advantages when only used in image devices (e.g., CRTs), since they can provide a higher resolution. A problem of light reabsorption inside white-emitting – especially mixed - phosphors exists. The ―short-wave‖ radiation – e.g., blue – is absorbed by the ―long-wave‖ (red or yellow) component of the mixture. The white-emitting phosphors for television possess the color temperature in the range of 5000 - 9000 К and chromaticity coordinates close to x=1/3, y=1/3. These parameters are not optimal for the lamp phosphors. Owing to the existing fundamental limitations, the energy efficiency of the known cathodoluminophores does not exceed 25%. The phosphors will be optimal with the emission chromaticity coordinates x=0.45-0.5, y=0.38-0.45 (color temperature of 2500-2800 К), i.e. located near the ―yellow border‖ of the white region where the lumen-equivalent is greater [4].