Phosphor

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Example of phosphorescence Luc Viatour phosphore poudre.jpg
Example of phosphorescence
Monochrome monitor IBM PC 5150.jpg
Monochrome monitor
Aperture grille CRT phosphors CRT Phosphors.jpg
Aperture grille CRT phosphors

A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or visible light, and cathodoluminescent substances which glow when struck by an electron beam (cathode rays) in a cathode-ray tube.

Contents

When a phosphor is exposed to radiation, the orbital electrons in its molecules are excited to a higher energy level; when they return to their former level they emit the energy as light of a certain color. Phosphors can be classified into two categories: fluorescent substances which emit the energy immediately and stop glowing when the exciting radiation is turned off, and phosphorescent substances which emit the energy after a delay, so they keep glowing after the radiation is turned off, decaying in brightness over a period of milliseconds to days.

Fluorescent materials are used in applications in which the phosphor is excited continuously: cathode-ray tubes (CRT) and plasma video display screens, fluoroscope screens, fluorescent lights, scintillation sensors, white LEDs, and luminous paints for black light art. Phosphorescent materials are used where a persistent light is needed, such as glow-in-the-dark watch faces and aircraft instruments, and in radar screens to allow the target 'blips' to remain visible as the radar beam rotates. CRT phosphors were standardized beginning around World War II and designated by the letter "P" followed by a number.

Phosphorus, the light-emitting chemical element for which phosphors are named, emits light due to chemiluminescence, not phosphorescence. [1]

Light-emission process

Jablonski diagram shows the energy levels in a fluorescing atom in a phosphor. An electron in the phosphor absorbs a high-energy photon from the applied radiation, exciting it to a higher energy level. After losing some energy in non-radiative transitions, it eventually transitions back to its ground state energy level by fluorescence, emitting a photon of lower energy in the visible light region. Jablonski Diagram of Fluorescence Only-en.svg
Jablonski diagram shows the energy levels in a fluorescing atom in a phosphor. An electron in the phosphor absorbs a high-energy photon from the applied radiation, exciting it to a higher energy level. After losing some energy in non-radiative transitions, it eventually transitions back to its ground state energy level by fluorescence, emitting a photon of lower energy in the visible light region.

The scintillation process in inorganic materials is due to the electronic band structure found in the crystals. An incoming particle can excite an electron from the valence band to either the conduction band or the exciton band (located just below the conduction band and separated from the valence band by an energy gap). This leaves an associated hole behind, in the valence band. Impurities create electronic levels in the forbidden gap.

The excitons are loosely bound electron–hole pairs that wander through the crystal lattice until they are captured as a whole by impurity centers. They then rapidly de-excite by emitting scintillation light (fast component).

In the conduction band, electrons are independent of their associated holes. Those electrons and holes are captured successively by impurity centers exciting certain metastable states not accessible to the excitons. The delayed de-excitation of those metastable impurity states, slowed by reliance on the low-probability forbidden mechanism, again results in light emission (slow component). In the case of inorganic scintillators, the activator impurities are typically chosen so that the emitted light is in the visible range or near-UV, where photomultipliers are effective.

Phosphors are often transition-metal compounds or rare-earth compounds of various types. In inorganic phosphors, these inhomogeneities in the crystal structure are created usually by addition of a trace amount of dopants, impurities called activators . (In rare cases dislocations or other crystal defects can play the role of the impurity.) The wavelength emitted by the emission center is dependent on the atom itself and on the surrounding crystal structure.

Materials

Phosphors are usually made from a suitable host material with an added activator. The best known type is a copper-activated zinc sulfide (ZnS) and the silver-activated zinc sulfide (zinc sulfide silver ).

The host materials are typically oxides, nitrides and oxynitrides, [2] sulfides, selenides, halides or silicates of zinc, cadmium, manganese, aluminium, silicon, or various rare-earth metals. The activators prolong the emission time (afterglow). In turn, other materials (such as nickel) can be used to quench the afterglow and shorten the decay part of the phosphor emission characteristics.

Many phosphor powders are produced in low-temperature processes, such as sol-gel, and usually require post-annealing at temperatures of ~1000 °C, which is undesirable for many applications. However, proper optimization of the growth process allows manufacturers to avoid the annealing. [3]

Phosphors used for fluorescent lamps require a multi-step production process, with details that vary depending on the particular phosphor. Bulk material must be milled to obtain a desired particle size range, since large particles produce a poor-quality lamp coating, and small particles produce less light and degrade more quickly. During the firing of the phosphor, process conditions must be controlled to prevent oxidation of the phosphor activators or contamination from the process vessels. After milling, the phosphor may be washed to remove minor excess of activator elements. Volatile elements must not be allowed to escape during processing. Lamp manufacturers have changed compositions of phosphors to eliminate some toxic elements formerly used, such as beryllium, cadmium, or thallium. [4]

The commonly quoted parameters for phosphors are the wavelength of emission maximum (in nanometers, or alternatively color temperature in kelvins for white blends), the peak width (in nanometers at 50% of intensity), and decay time (in seconds).

Examples:

Phosphor degradation

Many phosphors tend to lose efficiency gradually by several mechanisms. The activators can undergo change of valence (usually oxidation), the crystal lattice degrades, atoms – often the activators – diffuse through the material, the surface undergoes chemical reactions with the environment with consequent loss of efficiency or buildup of a layer absorbing the exciting and/or radiated energy, etc.

The degradation of electroluminescent devices depends on frequency of driving current, the luminance level, and temperature; moisture impairs phosphor lifetime very noticeably as well.

Harder, high-melting, water-insoluble materials display lower tendency to lose luminescence under operation. [7]

Examples:

Applications

Lighting

Phosphor layers provide most of the light produced by fluorescent lamps, and are also used to improve the balance of light produced by metal halide lamps. Various neon signs use phosphor layers to produce different colors of light. Electroluminescent displays found, for example, in aircraft instrument panels, use a phosphor layer to produce glare-free illumination or as numeric and graphic display devices. White LED lamps consist of a blue or ultra-violet emitter with a phosphor coating that emits at longer wavelengths, giving a full spectrum of visible light. Unfocused and undeflected cathode-ray tubes have been used as stroboscope lamps since 1958. [15]

Phosphor thermometry

Phosphor thermometry is a temperature measurement approach that uses the temperature dependence of certain phosphors. For this, a phosphor coating is applied to a surface of interest and, usually, the decay time is the emission parameter that indicates temperature. Because the illumination and detection optics can be situated remotely, the method may be used for moving surfaces such as high speed motor surfaces. Also, phosphor may be applied to the end of an optical fiber as an optical analog of a thermocouple.[ citation needed ]

Glow-in-the-dark toys

In these applications, the phosphor is directly added to the plastic used to mold the toys, or mixed with a binder for use as paints.

ZnS:Cu phosphor is used in glow-in-the-dark cosmetic creams frequently used for Halloween make-ups. Generally, the persistence of the phosphor increases as the wavelength increases. See also lightstick for chemiluminescence-based glowing items.

Oxygen sensing

Quenching of the triplet state by O2 (which has a triplet ground state) as a result of Dexter energy transfer is well known in solutions of phosphorescent heavy-metal complexes and doped polymers. [16] In recent years, phosphorescence porous materials(such as Metal–organic frameworks and Covalent organic frameworks) have shown promising oxygen sensing capabilities, for their non-linear gas-adsorption in ultra-low partial pressures of oxygen. [17] [18]

Postage stamps

Phosphor banded stamps first appeared in 1959 as guides for machines to sort mail. [19] Around the world many varieties exist with different amounts of banding. [20] Postage stamps are sometimes collected by whether or not they are "tagged" with phosphor (or printed on luminescent paper).

Radioluminescence

Zinc sulfide phosphors are used with radioactive materials, where the phosphor was excited by the alpha- and beta-decaying isotopes, to create luminescent paint for dials of watches and instruments (radium dials). Between 1913 and 1950 radium-228 and radium-226 were used to activate a phosphor made of silver doped zinc sulfide (ZnS:Ag), which gave a greenish glow. The phosphor is not suitable to be used in layers thicker than 25 mg/cm2, as the self-absorption of the light then becomes a problem. Furthermore, zinc sulfide undergoes degradation of its crystal lattice structure, leading to gradual loss of brightness significantly faster than the depletion of radium. ZnS:Ag coated spinthariscope screens were used by Ernest Rutherford in his experiments discovering atomic nucleus.

Copper doped zinc sulfide (ZnS:Cu) is the most common phosphor used and yields blue-green light. Copper and magnesium doped zinc sulfide (ZnS:Cu,Mg) yields yellow-orange light.

Tritium is also used as a source of radiation in various products utilizing tritium illumination.

Electroluminescence

Electroluminescence can be exploited in light sources. Such sources typically emit from a large area, which makes them suitable for backlights of LCD displays. The excitation of the phosphor is usually achieved by application of high-intensity electric field, usually with suitable frequency. Current electroluminescent light sources tend to degrade with use, resulting in their relatively short operation lifetimes.

ZnS:Cu was the first formulation successfully displaying electroluminescence, tested at 1936 by Georges Destriau in Madame Marie Curie laboratories in Paris.

Powder or AC electroluminescence is found in a variety of backlight and night light applications. Several groups offer branded EL offerings (e.g. IndiGlo used in some Timex watches) or "Lighttape", another trade name of an electroluminescent material, used in electroluminescent light strips. The Apollo space program is often credited with being the first significant use of EL for backlights and lighting. [21]

White LEDs

White light-emitting diodes are usually blue InGaN LEDs with a coating of a suitable material. Cerium(III)-doped YAG (YAG:Ce3+, or Y3Al5O12:Ce3+) is often used; it absorbs the light from the blue LED and emits in a broad range from greenish to reddish, with most of its output in yellow. This yellow emission combined with the remaining blue emission gives the "white" light, which can be adjusted to color temperature as warm (yellowish) or cold (bluish) white. The pale yellow emission of the Ce3+:YAG can be tuned by substituting the cerium with other rare-earth elements such as terbium and gadolinium and can even be further adjusted by substituting some or all of the aluminium in the YAG with gallium. However, this process is not one of phosphorescence. The yellow light is produced by a process known as scintillation, the complete absence of an afterglow being one of the characteristics of the process.

Some rare-earth-doped Sialons are photoluminescent and can serve as phosphors. Europium(II)-doped β-SiAlON absorbs in ultraviolet and visible light spectrum and emits intense broadband visible emission. Its luminance and color does not change significantly with temperature, due to the temperature-stable crystal structure. It has a great potential as a green down-conversion phosphor for white LEDs; a yellow variant also exists (α-SiAlON [22] ). For white LEDs, a blue LED is used with a yellow phosphor, or with a green and yellow SiAlON phosphor and a red CaAlSiN3-based (CASN) phosphor. [23] [24] [25]

White LEDs can also be made by coating near-ultraviolet-emitting LEDs with a mixture of high-efficiency europium-based red- and blue-emitting phosphors plus green-emitting copper- and aluminium-doped zinc sulfide (ZnS:Cu,Al). This is a method analogous to the way fluorescent lamps work.

Some newer white LEDs use a yellow and blue emitter in series, to approximate white; this technology is used in some Motorola phones such as the Blackberry as well as LED lighting and the original-version stacked emitters by using GaN on SiC on InGaP but was later found to fracture at higher drive currents.

Many white LEDs used in general lighting systems can be used for data transfer, as, for example, in systems that modulate the LED to act as a beacon. [26]

It is also common for white LEDs to use phosphors other than Ce:YAG, or to use two or three phosphors to achieve a higher CRI, often at the cost of efficiency. Examples of additional phosphors are R9, which produces a saturated red, nitrides which produce red, and aluminates such as lutetium aluminum garnet that produce green. Silicate phosphors are brighter but fade more quickly, and are used in LCD LED backlights in mobile devices. LED phosphors can be placed directly over the die or made into a dome and placed above the LED: this approach is known as a remote phosphor. [27] Some colored LEDs, instead of using a colored LED, use a blue LED with a colored phosphor because such an arrangement is more efficient than a colored LED. Oxynitride phosphors can also be used in LEDs. The precursors used to make the phosphors may degrade when exposed to air. [28]

Cathode-ray tubes

Spectra of constituent blue, green and red phosphors in a common cathode-ray tube CRT phosphors.png
Spectra of constituent blue, green and red phosphors in a common cathode-ray tube

Cathode-ray tubes produce signal-generated light patterns in a (typically) round or rectangular format. Bulky CRTs were used in the black-and-white household television (TV) sets that became popular in the 1950s, as well as first-generation, tube-based color TVs, and most earlier computer monitors. CRTs have also been widely used in scientific and engineering instrumentation, such as oscilloscopes, usually with a single phosphor color, typically green. Phosphors for such applications may have long afterglow, for increased image persistence.

The phosphors can be deposited as either thin film, or as discrete particles, a powder bound to the surface. Thin films have better lifetime and better resolution, but provide less bright and less efficient image than powder ones. This is caused by multiple internal reflections in the thin film, scattering the emitted light.

White (in black-and-white): The mix of zinc cadmium sulfide and zinc sulfide silver, the ZnS:Ag + (Zn,Cd)S:Ag is the white P4 phosphor used in black and white television CRTs. Mixes of yellow and blue phosphors are usual. Mixes of red, green and blue, or a single white phosphor, can also be encountered.

Red: Yttrium oxide-sulfide activated with europium is used as the red phosphor in color CRTs. The development of color TV took a long time due to the search for a red phosphor. The first red emitting rare-earth phosphor, YVO4:Eu3+, was introduced by Levine and Palilla as a primary color in television in 1964. [29] In single crystal form, it was used as an excellent polarizer and laser material. [30]

Yellow: When mixed with cadmium sulfide, the resulting zinc cadmium sulfide(Zn,Cd)S:Ag, provides strong yellow light.

Green: Combination of zinc sulfide with copper, the P31 phosphor or ZnS:Cu, provides green light peaking at 531 nm, with long glow.

Blue: Combination of zinc sulfide with few ppm of silver, the ZnS:Ag, when excited by electrons, provides strong blue glow with maximum at 450 nm, with short afterglow with 200 nanosecond duration. It is known as the P22B phosphor. This material, zinc sulfide silver, is still one of the most efficient phosphors in cathode-ray tubes. It is used as a blue phosphor in color CRTs.

The phosphors are usually poor electrical conductors. This may lead to deposition of residual charge on the screen, effectively decreasing the energy of the impacting electrons due to electrostatic repulsion (an effect known as "sticking"). To eliminate this, a thin layer of aluminium (about 100 nm) is deposited over the phosphors, usually by vacuum evaporation, and connected to the conductive layer inside the tube. This layer also reflects the phosphor light to the desired direction, and protects the phosphor from ion bombardment resulting from an imperfect vacuum.

To reduce the image degradation by reflection of ambient light, contrast can be increased by several methods. In addition to black masking of unused areas of screen, the phosphor particles in color screens are coated with pigments of matching color. For example, the red phosphors are coated with ferric oxide (replacing earlier Cd(S,Se) due to cadmium toxicity), blue phosphors can be coated with marine blue (CoO·n Al
2
O
3
) or ultramarine (Na
8
Al
6
Si
6
O
24
S
2
). Green phosphors based on ZnS:Cu do not have to be coated due to their own yellowish color. [7]

Black-and-white television CRTs

The black-and-white television screens require an emission color close to white. Usually, a combination of phosphors is employed.

The most common combination is ZnS:Ag + (Zn,Cd)S:Cu,Al (blue + yellow). Other ones are ZnS:Ag + (Zn,Cd)S:Ag (blue + yellow), and ZnS:Ag + ZnS:Cu,Al + Y2O2S:Eu3+ (blue + green + red – does not contain cadmium and has poor efficiency). The color tone can be adjusted by the ratios of the components.

As the compositions contain discrete grains of different phosphors, they produce image that may not be entirely smooth. A single, white-emitting phosphor, (Zn,Cd)S:Ag,Au,Al overcomes this obstacle. Due to its low efficiency, it is used only on very small screens.

The screens are typically covered with phosphor using sedimentation coating, where particles suspended in a solution are let to settle on the surface. [31]

Reduced-palette color CRTs

For displaying of a limited palette of colors, there are a few options.

In beam penetration tubes, different color phosphors are layered and separated with dielectric material. The acceleration voltage is used to determine the energy of the electrons; lower-energy ones are absorbed in the top layer of the phosphor, while some of the higher-energy ones shoot through and are absorbed in the lower layer. So either the first color or a mixture of the first and second color is shown. With a display with red outer layer and green inner layer, the manipulation of accelerating voltage can produce a continuum of colors from red through orange and yellow to green.

Another method is using a mixture of two phosphors with different characteristics. The brightness of one is linearly dependent on electron flux, while the other one's brightness saturates at higher fluxes—the phosphor does not emit any more light regardless of how many more electrons impact it. At low electron flux, both phosphors emit together; at higher fluxes, the luminous contribution of the nonsaturating phosphor prevails, changing the combined color. [31]

Such displays can have high resolution, due to absence of two-dimensional structuring of RGB CRT phosphors. Their color palette is, however, very limited. They were used e.g. in some older military radar displays.

Color television CRTs

The phosphors in color CRTs need higher contrast and resolution than the black-and-white ones. The energy density of the electron beam is about 100 times greater than in black-and-white CRTs; the electron spot is focused to about 0.2 mm diameter instead of about 0.6 mm diameter of the black-and-white CRTs. Effects related to electron irradiation degradation are therefore more pronounced.

Color CRTs require three different phosphors, emitting in red, green and blue, patterned on the screen. Three separate electron guns are used for color production (except for displays that use beam-index tube technology, which is rare). The red phosphor has always been a problem, being the dimmest of the three necessitating the brighter green and blue electron beam currents be adjusted down to make them equal the red phosphor's lower brightness. This made early color TVs only usable indoors as bright light made it impossible to see the dim picture, while portable black-and-white TVs viewable in outdoor sunlight were already common.

The composition of the phosphors changed over time, as better phosphors were developed and as environmental concerns led to lowering the content of cadmium and later abandoning it entirely. The (Zn,Cd)S:Ag,Cl was replaced with (Zn,Cd)S:Cu,Al with lower cadmium/zinc ratio, and then with cadmium-free ZnS:Cu,Al.

The blue phosphor stayed generally unchanged, a silver-doped zinc sulfide. The green phosphor initially used manganese-doped zinc silicate, then evolved through silver-activated cadmium-zinc sulfide, to lower-cadmium copper-aluminium activated formula, and then to cadmium-free version of the same. The red phosphor saw the most changes; it was originally manganese-activated zinc phosphate, then a silver-activated cadmium-zinc sulfide, then the europium(III) activated phosphors appeared; first in an yttrium vanadate matrix, then in yttrium oxide and currently in yttrium oxysulfide. The evolution of the phosphors was therefore (ordered by B-G-R):

  • ZnS:Ag  Zn2SiO4:Mn  Zn3(PO4)2:Mn
  • ZnS:Ag  (Zn,Cd)S:Ag  (Zn,Cd)S:Ag
  • ZnS:Ag  (Zn,Cd)S:Ag  YVO4:Eu3+ (1964?)
  • ZnS:Ag  (Zn,Cd)S:Cu,Al  Y2O2S:Eu3+ or Y2O3:Eu3+
  • ZnS:Ag  ZnS:Cu,Al or ZnS:Au,Cu,Al  Y2O2S:Eu3+ [31]

Projection televisions

For projection televisions, where the beam power density can be two orders of magnitude higher than in conventional CRTs, some different phosphors have to be used.

For blue color, ZnS:Ag,Cl is employed. However, it saturates. (La,Gd)OBr:Ce,Tb3+ can be used as an alternative that is more linear at high energy densities.

For green, a terbium-activated Gd2O2Tb3+; its color purity and brightness at low excitation densities is worse than the zinc sulfide alternative, but it behaves linear at high excitation energy densities, while zinc sulfide saturates. However, it also saturates, so Y3Al5O12:Tb3+ or Y2SiO5:Tb3+ can be substituted. LaOBr:Tb3+ is bright but water-sensitive, degradation-prone, and the plate-like morphology of its crystals hampers its use; these problems are solved now, so it is gaining use due to its higher linearity.

Y2O2S:Eu3+ is used for red emission. [31]

Standard phosphor types

Standard phosphor types [32] [33]
Phosphor Composition Color Wavelength Peak widthPersistenceUsageNotes
P1, GJ Zn2SiO4:Mn (Willemite)Green525 nm40 nm [34] 1-100msCRT, LampOscilloscopes and monochrome monitors
P2ZnS:Cu(Ag)(B*)Blue-Green543 nmLongCRTOscilloscopes
P3Zn8:BeSi5O19:MnYellow602 nmMedium/13 msCRT Amber monochrome monitors
P4ZnS:Ag+(Zn,Cd)S:AgWhite565,540 nmShortCRTBlack and white TV CRTs and display tubes.
P4 (Cd-free)ZnS:Ag+ZnS:Cu+Y2O2S:EuWhiteShortCRTBlack and white TV CRTs and display tubes, Cd free.
P5 CaWO4:WBlue430 nmVery ShortCRTFilm
P6ZnS:Ag+ZnS:CdS:AgWhite565,460 nmShortCRT
P7(Zn,Cd)S:CuBlue with Yellow persistence558,440 nmLongCRT Radar PPI, old EKG monitors, early oscilloscopes
P10KClgreen-absorbing scotophor Long Dark-trace CRTs Radar screens; turns from translucent white to dark magenta, stays changed until erased by heating or infrared light
P11, BEZnS:Ag,Cl or ZnS:ZnBlue460 nm0.01-1 msCRT, VFDDisplay tubes and VFDs; Oscilloscopes (for fast photographic recording) [35]
P12Zn(Mg)F2:MnOrange590 nmMedium/longCRT Radar
P13MgSi2O6:MnReddish Orange-Reddish Orange640 nmMediumCRTFlying spot scanning systems and photographic applications
P14ZnS:Ag on ZnS:CdS:CuBlue with Orange persistenceMedium/longCRT Radar PPI, old EKG monitors
P15ZnO:ZnBlue-Green504,391 nmExtremely ShortCRTTelevision pickup by flying-spot scanning
P16CaMgSi2O6:CeBluish Purple-Bluish Purple380 nmVery ShortCRTFlying spot scanning systems and photographic applications
P17ZnO,ZnCdS:CuBlue-Yellow504,391 nmBlue-Short, Yellow-LongCRT
P18CaMgSi2O6:Ti, BeSi2O6:Mnwhite-white545,405 nmMedium to ShortCRT
P19, LF(KF,MgF2):MnOrange-Yellow590 nmLongCRTRadar screens
P20, KA(Zn,Cd)S:Ag or (Zn,Cd)S:CuYellow-green555 nm1–100 msCRTDisplay tubes
P21MgF2:Mn2+Reddish605 nmCRT, RadarRegistered by Allen B DuMont Laboratories
P22RY2O2S:Eu+Fe2O3Red611 nmShortCRTRed phosphor for TV screens
P22GZnS:Cu,AlGreen530 nmShortCRTGreen phosphor for TV screens
P22BZnS:Ag+Co-on-Al2O3 BlueShortCRTBlue phosphor for TV screens
P23ZnS:Ag+(Zn,Cd)S:AgWhite575,460 nmShortCRT, Direct viewing televisionRegistered by United States Radium Corporation.
P24, GE ZnO:ZnGreen505 nm1–10 μsVFDmost common phosphor in vacuum fluorescent displays. [36]
P25CaSi2O6:Pb:MnOrange-Orange610 nmMediumCRTMilitary Displays - 7UP25 CRT
P26, LC(KF,MgF2):MnOrange595 nmLongCRTRadar screens
P27ZnPO4:MnReddish Orange-Reddish Orange635 nmMediumCRTColor TV monitor service
P28, KE(Zn,Cd)S:Cu,ClYellowMediumCRTDisplay tubes
P29Alternating P2 and P25 stripesBlue-Green/Orange stripesMediumCRTRadar screens
P31, GHZnS:Cu or ZnS:Cu,AgYellowish-green0.01-1 msCRTOscilloscopes and monochrome monitors
P33, LDMgF2:MnOrange590 nm> 1secCRTRadar screens
P34Bluish Green-Yellow GreenVery LongCRT
P35ZnS,ZnSe:AgBlue White-Blue White455 nmMedium ShortCRTPhotographic registration on orthochromatic film materials
P38, LK(Zn,Mg)F2:MnOrange-Yellow590 nmLongCRTRadar screens
P39, GR Zn2SiO4:Mn,AsGreen525 nmLongCRTDisplay tubes
P40, GAZnS:Ag+(Zn,Cd)S:CuWhiteLongCRTDisplay tubes
P43, GY Gd2O2S:TbYellow-green545 nmMediumCRTDisplay tubes, Electronic Portal Imaging Devices (EPIDs) used in radiation therapy linear accelerators for cancer treatment
P45, WBY2O2S:TbWhite545 nmShortCRTViewfinders
P46, KG Y3Al5O12:CeGreen530 nmVery short (70ns)CRT Beam-index tube
P47, BH Y2SiO5:CeBlue400 nmVery shortCRTBeam-index tube
P53, KJ Y3Al5O12:TbYellow-green544 nmShortCRTProjection tubes
P55, BMZnS:Ag,AlBlue450 nmShortCRTProjection tubes
ZnS:AgBlue450 nmCRT
ZnS:Cu,Al or ZnS:Cu,Au,AlGreen530 nmCRT
(Zn,Cd)S:Cu,Cl+(Zn,Cd)S:Ag,ClWhiteCRT
Y2SiO5:TbGreen545 nmCRTProjection tubes
Y2OS:TbGreen545 nmCRTDisplay tubes
Y3(Al,Ga)5O12:CeGreen520 nmShortCRTBeam-index tube
Y3(Al,Ga)5O12:TbYellow-green544 nmShortCRTProjection tubes
InBO3:TbYellow-green550 nmCRT
InBO3:EuYellow588 nmCRT
InBO3:Tb+InBO3:EuamberCRTComputer displays
InBO3:Tb+InBO3:Eu+ZnS:AgWhiteCRT
(Ba,Eu)Mg2Al16O27BlueLampTrichromatic fluorescent lamps
(Ce,Tb)MgAl11O19Green546 nm9 nmLampTrichromatic fluorescent lamps [34]
BAMBaMgAl10O17:Eu,MnBlue450 nmLamp, displaysTrichromatic fluorescent lamps
BaMg2Al16O27:Eu(II)Blue450 nm52 nmLampTrichromatic fluorescent lamps [34]
BAMBaMgAl10O17:Eu,MnBlue-Green456 nm,514 nmLamp
BaMg2Al16O27:Eu(II),Mn(II)Blue-Green456 nm, 514 nm50 nm 50% [34] Lamp
Ce0.67Tb0.33MgAl11O19:Ce,TbGreen543 nmLampTrichromatic fluorescent lamps
Zn2SiO4:Mn,Sb2O3Green528 nmLamp
CaSiO3:Pb,MnOrange-Pink615 nm83 nm [34] Lamp
CaWO4 (Scheelite)Blue417 nmLamp
CaWO4:PbBlue433 nm/466 nm111 nmLampWide bandwidth [34]
MgWO4 Blue pale473 nm118 nmLampWide bandwidth, deluxe blend component [34]
(Sr,Eu,Ba,Ca)5(PO4)3ClBlueLampTrichromatic fluorescent lamps
Sr5Cl(PO4)3:Eu(II)Blue447 nm32 nm [34] Lamp
(Ca,Sr,Ba)3(PO4)2Cl2:EuBlue452 nmLamp
(Sr,Ca,Ba)10(PO4)6Cl2:EuBlue453 nmLampTrichromatic fluorescent lamps
Sr2P2O7:Sn(II) Blue460 nm98 nmLampWide bandwidth, deluxe blend component [34]
Sr6P5BO20:EuBlue-Green480 nm82 nm [34] Lamp
Ca5F(PO4)3:SbBlue482 nm117 nmLampWide bandwidth [34]
(Ba,Ti)2P2O7:TiBlue-Green494 nm143 nmLampWide bandwidth, deluxe blend component [34]
3Sr3(PO4)2.SrF2:Sb,MnBlue502 nmLamp
Sr5F(PO4)3:Sb,MnBlue-Green509 nm127 nmLampWide bandwidth [34]
Sr5F(PO4)3:Sb,MnBlue-Green509 nm127 nmLampWide bandwidth [34]
LaPO4:Ce,TbGreen544 nmLampTrichromatic fluorescent lamps
(La,Ce,Tb)PO4GreenLampTrichromatic fluorescent lamps
(La,Ce,Tb)PO4:Ce,TbGreen546 nm6 nmLampTrichromatic fluorescent lamps [34]
Ca3(PO4)2.CaF2:Ce,MnYellow568 nmLamp
(Ca,Zn,Mg)3(PO4)2:SnOrange-pink610 nm146 nmLampWide bandwidth, blend component [34]
(Zn,Sr)3(PO4)2:MnOrange-Red625 nmLamp
(Sr,Mg)3(PO4)2:SnOrange-pinkish white626 nm120 nmFluorescent lampsWide bandwidth, deluxe blend component [34]
(Sr,Mg)3(PO4)2:Sn(II)Orange-red630 nmFluorescent lamps
Ca5F(PO4)3:Sb,Mn3800KFluorescent lampsLite-white blend [34]
Ca5(F,Cl)(PO4)3:Sb,MnWhite-Cold/WarmFluorescent lamps2600 to 9900 K, for very high output lamps [34]
(Y,Eu)2O3RedLampTrichromatic fluorescent lamps
Y2O3:Eu(III) Red611 nm4 nmLampTrichromatic fluorescent lamps [34]
Mg4(F)GeO6:MnRed658 nm17 nmHigh-pressure mercury lamps [34]
Mg4(F)(Ge,Sn)O6:MnRed658 nmLamp
Y(P,V)O4:EuOrange-Red619 nmLamp
YVO4:EuOrange-Red619 nmHigh Pressure Mercury and Metal Halide Lamps
Y2O2S:EuRed626 nmLamp
3.5  MgO  · 0.5 MgF2 · GeO2 :MnRed655 nmLamp3.5  MgO  · 0.5  MgF2  ·  GeO2  :Mn
Mg5As2O11:MnRed660 nmHigh-pressure mercury lamps, 1960s
SrAl2O7:PbUltraviolet313 nmSpecial fluorescent lamps for medical useUltraviolet
CAMLaMgAl11O19:CeUltraviolet340 nm52 nmBlack-light fluorescent lampsUltraviolet
LAPLaPO4:CeUltraviolet320 nm38 nmMedical and scientific UV lampsUltraviolet
SACSrAl12O19:CeUltraviolet295 nm34 nmLampUltraviolet
SrAl11Si0.75O19:Ce0.15Mn0.15Green515 nm22 nmLampMonochromatic lamps for copiers [37]
BSPBaSi2O5:PbUltraviolet350 nm40 nmLampUltraviolet
SrFB2O3:Eu(II)Ultraviolet366 nmLampUltraviolet
SBESrB4O7:EuUltraviolet368 nm15 nmLampUltraviolet
SMSSr2MgSi2O7:PbUltraviolet365 nm68 nmLampUltraviolet
MgGa2O4:Mn(II)Blue-GreenLampBlack light displays

Various

Some other phosphors commercially available, for use as X-ray screens, neutron detectors, alpha particle scintillators, etc., are:

See also

Related Research Articles

<span class="mw-page-title-main">Cathode-ray tube</span> Vacuum tube often used to display images

A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a frame of video on an analog television set (TV), digital raster graphics on a computer monitor, or other phenomena like radar targets. A CRT in a TV is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. The term cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons.

<span class="mw-page-title-main">Electroluminescence</span> Optical and electrical phenomenon

Electroluminescence (EL) is an optical and electrical phenomenon, in which a material emits light in response to the passage of an electric current or to a strong electric field. This is distinct from black body light emission resulting from heat (incandescence), chemical reactions (chemiluminescence), reactions in a liquid (electrochemiluminescence), sound (sonoluminescence), or other mechanical action (mechanoluminescence), or organic electroluminescence.

<span class="mw-page-title-main">Phosphorescence</span> Process in which energy absorbed by a substance is released relatively slowly in the form of light

Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluorescence, a phosphorescent material does not immediately reemit the radiation it absorbs. Instead, a phosphorescent material absorbs some of the radiation energy and reemits it for a much longer time after the radiation source is removed.

<span class="mw-page-title-main">Scintillator</span> Material which glows when excited by ionizing radiation

A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate. Sometimes, the excited state is metastable, so the relaxation back down from the excited state to lower states is delayed. The process then corresponds to one of two phenomena: delayed fluorescence or phosphorescence. The correspondence depends on the type of transition and hence the wavelength of the emitted optical photon.

<span class="mw-page-title-main">Vacuum fluorescent display</span> Display used in consumer electronics

A vacuum fluorescent display (VFD) is a display device once commonly used on consumer electronics equipment such as video cassette recorders, car radios, and microwave ovens.

<span class="mw-page-title-main">Zinc sulfide</span> Inorganic compound

Zinc sulfide is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various impurities, the pure material is white, and it is widely used as a pigment. In its dense synthetic form, zinc sulfide can be transparent, and it is used as a window for visible optics and infrared optics.

<span class="mw-page-title-main">Tritium radioluminescence</span> Use of gaseous tritium to create visible light

Tritium radioluminescence is the use of gaseous tritium, a radioactive isotope of hydrogen, to create visible light. Tritium emits electrons through beta decay and, when they interact with a phosphor material, light is emitted through the process of phosphorescence. The overall process of using a radioactive material to excite a phosphor and ultimately generate light is called radioluminescence. As tritium illumination requires no electrical energy, it has found wide use in applications such as emergency exit signs, illumination of wristwatches, and portable yet very reliable sources of low intensity light which won't degrade human night vision. Gun sights for night use and small lights used mostly by military personnel fall under the latter application.

<span class="mw-page-title-main">Yttrium aluminium garnet</span> Synthetic crystalline material of the garnet group

Yttrium aluminium garnet (YAG, Y3Al5O12) is a synthetic crystalline material of the garnet group. It is a cubic yttrium aluminium oxide phase, with other examples being YAlO3 (YAP) in a hexagonal or an orthorhombic, perovskite-like form, and the monoclinic Y4Al2O9 (YAM).

<span class="mw-page-title-main">Screen burn-in</span> Disfigurement of an electronic display

Screen burn-in, image burn-in, ghost image, or shadow image, is a permanent discoloration of areas on an electronic display such as a cathode ray tube (CRT) in an old computer monitor or television set. It is caused by cumulative non-uniform use of the screen.

<span class="mw-page-title-main">Radioluminescence</span> Light produced in a material by bombardment with ionizing radiation

Radioluminescence is the phenomenon by which light is produced in a material by bombardment with ionizing radiation such as alpha particles, beta particles, or gamma rays. Radioluminescence is used as a low level light source for night illumination of instruments or signage. Radioluminescent paint is occasionally used for clock hands and instrument dials, enabling them to be read in the dark. Radioluminescence is also sometimes seen around high-power radiation sources, such as nuclear reactors and radioisotopes.

<span class="mw-page-title-main">Zinc selenide</span> Chemical compound

Zinc selenide is the inorganic compound with the formula ZnSe. It is a lemon-yellow solid although most samples have a duller color due to the effects of oxidation. It is an intrinsic semiconductor with a band gap of about 2.70 eV at 25 °C (77 °F), equivalent to a wavelength of 459 nm. ZnSe occurs as the rare mineral stilleite, named after Hans Stille.

Luminous paint is paint that emits visible light through fluorescence, phosphorescence, or radioluminescence.

<span class="mw-page-title-main">Strontium aluminate</span> Chemical compound

Strontium aluminate is an aluminate compound with the chemical formula SrAl2O4. It is a pale yellow, monoclinic crystalline powder that is odourless and non-flammable. When activated with a suitable dopant, it acts as a photoluminescent phosphor with long persistence of phosphorescence.

<span class="mw-page-title-main">Large-screen television technology</span> Technology rapidly developed in the late 1990s and 2000s

Large-screen television technology developed rapidly in the late 1990s and 2000s. Prior to the development of thin-screen technologies, rear-projection television was standard for larger displays, and jumbotron, a non-projection video display technology, was used at stadiums and concerts. Various thin-screen technologies are being developed, but only liquid crystal display (LCD), plasma display (PDP) and Digital Light Processing (DLP) have been publicly released. Recent technologies like organic light-emitting diode (OLED) as well as not-yet-released technologies like surface-conduction electron-emitter display (SED) or field emission display (FED) are in development to supersede earlier flat-screen technologies in picture quality.

<span class="mw-page-title-main">Monochrome monitor</span> Type of CRT computer monitor

A monochrome monitor is a type of computer monitor in which computer text and images are displayed in varying tones of only one color, as opposed to a color monitor that can display text and images in multiple colors. They were very common in the early days of computing, from the 1960s through the 1980s, before color monitors became widely commercially available. They are still widely used in applications such as computerized cash register systems, owing to the age of many registers. Green screen was the common name for a monochrome monitor using a green "P1" phosphor screen; the term is often misused to refer to any block mode display terminal, regardless of color, e.g., IBM 3279, 3290.

<span class="mw-page-title-main">Super-LumiNova</span> Photoluminescent pigment

Super-LumiNova is a brand name under which strontium aluminate–based non-radioactive and nontoxic photoluminescent or afterglow pigments for illuminating markings on watch dials, hands and bezels, etc. in the dark are marketed. When activated with a suitable dopant, it acts as a photoluminescent phosphor with long persistence of phosphorescence. This technology offers up to ten times higher brightness than previous zinc sulfide–based materials.

In phosphors and scintillators, the activator is the element added as dopant to the crystal of the material to create desired type of nonhomogeneities.

A scotophor is a material showing reversible darkening and bleaching when subjected to certain types of radiation. The name means dark bearer, in contrast to phosphor, which means light bearer. Scotophors show tenebrescence and darken when subjected to an intense radiation such as sunlight. Minerals showing such behavior include hackmanite sodalite, spodumene and tugtupite. Some pure alkali halides also show such behavior.

Quantum dots (QDs) are semiconductor nanoparticles with a size less than 10 nm. They exhibited size-dependent properties especially in the optical absorption and the photoluminescence (PL). Typically, the fluorescence emission peak of the QDs can be tuned by changing their diameters. So far, QDs were consisted of different group elements such as CdTe, CdSe, CdS in the II-VI category, InP or InAs in the III-V category, CuInS2 or AgInS2 in the I–III–VI2 category, and PbSe/PbS in the IV-VI category. These QDs are promising candidates as fluorescent labels in various biological applications such as bioimaging, biosensing and drug delivery.

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Bibliography