Editing Phosphor (section)

==Materials==
Phosphors are usually made from a suitable host material with an added [[activator (phosphor)|activator]]. The best known type is a copper-activated [[Zinc sulfide|zinc sulfide (ZnS)]] and the [[silver]]-activated zinc sulfide (''zinc sulfide [[silver]]'').

The host materials are typically [[oxide]]s, [[nitride]]s and oxynitrides,<ref>{{cite journal| title =Silicon-based oxynitride and nitride phosphors for white LEDs—A review|journal = Sci. Technol. Adv. Mater. |volume =8| year =2007|page = 588|doi= 10.1016/j.stam.2007.08.005|author =Xie, Rong-Jun| first2 =Naoto| last2 =Hirosaki|bibcode = 2007STAdM...8..588X| issue =7–8 |doi-access =free}}{{open access}}</ref> [[sulfide]]s, [[selenide]]s, [[halide]]s or [[silicate]]s of [[zinc]], [[cadmium]], [[manganese]], [[aluminium]], [[silicon]], or various [[rare-earth metal]]s. 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&nbsp;°C, which is undesirable for many applications. However, proper optimization of the growth process allows manufacturers to avoid the annealing.<ref>{{cite journal| title =Fine yellow α-SiAlON:Eu phosphors for white LEDs prepared by the gas-reduction–nitridation method|journal = Sci. Technol. Adv. Mater.|volume = 8| year =2007|page =601|doi = 10.1016/j.stam.2007.09.003|author =Li, Hui-Li| first2 =Naoto| first3 =Rong-Jun| first4 =Takayuki| first5 =Mamoru| last2 =Hirosaki| last3 =Xie| last4 =Suehiro| last5 =Mitomo|bibcode = 2007STAdM...8..601L| issue =7–8 | doi-access =free}}{{open access}}</ref>

Phosphors used for [[fluorescent lamp]]s 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 [[pottery firing|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]].<ref>Kane, Raymond and Sell, Heinz (2001) ''Revolution in lamps: a chronicle of 50 years of progress'', 2nd ed. The Fairmont Press. {{ISBN|0-88173-378-4}}. Chapter 5 extensively discusses history, application and manufacturing of phosphors for lamps.</ref>

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

Examples:
* [[Calcium sulfide]] with [[strontium sulfide]] with [[bismuth]] as activator, {{chem2|(Ca,Sr)S:Bi}}, yields blue light with glow times up to 12 hours, red and orange are modifications of the zinc sulfide formula. Red color can be obtained from strontium sulfide.
* [[Zinc sulfide]] with about 5 ppm of a [[copper]] activator is the most common phosphor for the glow-in-the-dark toys and items. It is also called '''GS''' phosphor.
*Mix of zinc sulfide and [[cadmium sulfide]] emit color depending on their ratio; increasing of the CdS content shifts the output color towards longer wavelengths; its persistence ranges between 1–10 hours.
* [[Strontium aluminate]] activated by [[europium]] or [[dysprosium]], SrAl<sub>2</sub>O<sub>4</sub>:Eu(II):Dy(III), is a material developed in 1993 by Nemoto & Co. engineer Yasumitsu Aoki with higher brightness and significantly longer glow persistence; it produces green and aqua hues, where green gives the highest brightness and aqua the longest glow time.<ref name=jotes>{{Cite journal|last1=Matsuzawa|first1=T.|last2=Aoki|first2=Y.|last3=Takeuchi|first3=N.|last4=Murayama|first4=Y.|date=1996-08-01|title=A New Long Phosphorescent Phosphor with High Brightness, SrAl<sub>2</sub>O<sub>4</sub>: Eu<sup>2+</sup>, Dy<sup>3+</sup>|url=https://iopscience.iop.org/article/10.1149/1.1837067|journal=Journal of the Electrochemical Society|language=en|volume=143|issue=8|pages=2670–2673|doi=10.1149/1.1837067|bibcode=1996JElS..143.2670M |issn=0013-4651|url-access=subscription}}</ref><ref>{{Cite patent|number=US5424006A|title=Phosphorescent phosphor|gdate=1994-02-25|url=https://patents.google.com/patent/US5424006A/en}}</ref> SrAl<sub>2</sub>O<sub>4</sub>:Eu:Dy is about 10 times brighter, 10 times longer glowing, and 10 times more expensive than ZnS:Cu.<ref name=jotes /> The excitation [[wavelengths]] for strontium aluminate range from 200 to 450&nbsp;nm. The wavelength for its green formulation is 520&nbsp;nm, its blue-green version emits at 505&nbsp;nm, and the blue one emits at 490&nbsp;nm. Colors with longer [[wavelengths]] can be obtained from the strontium aluminate as well, though for the price of some loss of brightness.