Phosphor in cathode ray

Cobalt is used as a blue phosphor in cathode ray tubes for television, in the coloration of polymers and leather goods, and as a pigment for oil and watercolor paints. Organic cobalt compounds that are used as colorants usually contain the azo (51) or formazon (52) chromophores. 

The phosphor Tb +iInBOs has been promoted as a green phosphor in cathode-ray tubes and as a possible scintillator. It exhibits a quantum efficiency under cathode-ray excitation of 8%, and it is stable to intense electron beams. The emission lifetime of 7.5 ms, however, is likely to be too long for some applications. 

Pfahnl, A. Aging of electronic phosphors in cathode ray tubes. In Advances in Electron Tube Techniques, pp. 204-208. Pergamon, New York. 

Uses. The main appHcation for strontium is in the form of strontium compounds. The carbonate, used in cathode ray tubes (CRTs) for color televisions and color computer monitors, is used both in the manufacturing of the glass envelope of the CRT and in the phosphors which give the color. 

Hematite is used to coat the red emiting phosphor, Y2O2EU, which is used in cathode ray tubes (Franz et al., 1993 Merckhi and Feldmann, 2000). Hematite is also used in sensors for the detection of hydrocarbon gases and carbon monoxide. The sensitivity of the sensor can be improved by sintering the oxide with 0.09 mol ° mol Al at 850 °C (Han et al., 2001 and references therein). 

Industrial silver-activated zinc sulfide phosphors use the intense blue emission exclusively. The ZnS Ag phosphor for cathode ray tubes is obtained by firing zinc sulfide and silver nitrate at ca. 1000 °C in the presence of sodium chloride (coactivator Cl-) [5.318]. The afterglow can be further reduced by addition of 10-3-10-4% of nickel ions. 

ZnO Zn is a typical example of a self-activated phosphor. In the case of zinc oxide, it is an excess of zinc which enables the phosphor to luminesce. The production is carried out by thermal oxidation of crystallized zinc sulfide in air at ca. 400 °C. The green luminescence, with a broad maximum at 505 nm, has a very short decay time of 10-6 s. As a phosphor for cathode-ray tubes, ZnO.Zn is classified in the TEPAC list as P 24 and in the WTDS system as GE. 

The Worldwide Phosphor Type Designation System (WTDS) the optical data of the specifies phosphors for cathode-ray tubes [5.429]. It replaces several phosphor designation systems (e.g., TEPAC, Pro Electron) previously in use in various countries. The phosphors are characterized by two capital letters, the first giving the position of the emission color in the Kelly Charts of Color Designation ... 

The majority of phosphors for cathode-ray tubes are coated with an oxide, silicate, or phosphate before use to improve their processing properties and stability to bum-in. Pigmenting of Y202S Eu3+ with finely divided Fe203 and of ZnS Ag+ with ultramarine or cobalt aluminate is also known. The pigment, which has the same body-color as the emission color of the phosphor, absorbs incident ambient light, effecting an increase in contrast [5.430]. 

Phosphors for cathode-ray tubes, television screens, monitor screens, radar screens, and oscilloscopes are tested under electron excitation. Electron energy and density should be similar to the conditions of the tube in which the screen will be used. The phosphors are sedimented or brushed onto light-permeable screens and coated with an evaporated aluminum coating to dissipate charge. The luminescence brightness and color of the emitted light are measured with optical instruments such as photomultipliers or spectrophotometers. 

Phosphors and Cathode Ray Tubes. Studies in Inorganic Chemistry, no. 17. New York Elsevier, 1993. 

However, there is a very usefiil reason for determining the type of luminescence decay curve present. Confirming the presence of an exponential decay curve means that only one type of emitter is jn sent. If a logarithmic decay process is found, it usually means that more than one type of emitting center is present, or that two or more decay processes are operative. While this does not occur very often, it is useful to know if such is present. This phenomenon occurs more in cathode-ray phosphors than in lamp phosphors, i.e.- sulfides vs oxide- hosts. 

However, the above explanation applies to phosphors used in the past in cathode-ray tubes. 

It should be noted that all of the above phosphors were described in a companion book, "The Chemistry of Artificial Lighting Devices- Lamps, Phosphors and Cathode-Ray Tubes", published by Elsevier in 1993 (ISBN 0-444-81709-3). In this volume, the exact methods for manufacture of these phosphors were presented along with the exact formulas and materials required to do so. 

We will begin our survey of present-day devices utilizing phosphors by first addressing recent improvements made in cathode-ray tubes followed by fluorescent lamps and then other lighting devices. We will then address the devices that depend upon thin film deposition for manufacture of the appliance. All of these utilize phosphors in some way for light output. 

The terms X-ray phosphors and scintillators are often used in an interchangeable way. Some authors use the term X-ray phosphors when the application requires a powder screen, and the term scintillator when a single crystal is required. The physical processes in the luminescence of these two types of materials is, however, in principle the same and comparable to that in cathode ray phosphors (Chapter 7). 

Raue R., Vink A. T. and Welker T. 1989. Phosphors screens in cathode ray tubes for projection television Phillips, Technol. Rev. 44 335-347. 

Cathodoluminescence. Instead of UV radiation, this luminescence is produced by irradiating the sample with electrons (and therefore it usually occurs in a vacuum). This is the phenomenon used in cathode ray tubes (CRTs) (including old TV screens) that were coated on the inside with a ceramic phosphor. 

In colored cathode ray tubes (CRTs), such as those used in televisions and computer terminals, three electron gun beams are focused on three different sets of phosphor dots on the front face of the tube. The dots are produced by using a compHcated photoHthography process. The phosphor dots are produced by settling the three different phosphors, each of which emits one of the primary saturated colors, red, green, or blue. Each phosphor is deposited separately and the three dots in each set are closely spaced so that the three primary colors are not resolved at normal viewing distances. Instead the viewer has the impression that there is only one color, the color achieved when the three primary colors are added together. 

Donor and acceptor levels are the active centers in most phosphors, as in zinc sulfide [1314-98-3] ZnS, containing an activator such as Cu and various co-activators. Phosphors are coated onto the inside of fluorescent lamps to convert the intense ultraviolet and blue from the mercury emissions into lower energy light to provide a color balance closer to daylight as in Figure 11. Phosphors can also be stimulated directly by electricity as in the Destriau effect in electroluminescent panels and by an electron beam as in the cathodoluminescence used in television and cathode ray display tubes and in (usually blue) vacuum-fluorescence alphanumeric displays. 

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