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In the old days computer monitors and televisions were built from cathode ray tubes (CRTs) where the image was generated by an electron beam hitting phosphors which emitted light approximating the three primary colours.

What were the phosphors made from and what were the key reasons why the particular substances were chosen?

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    $\begingroup$ "In the old days"? Like 5-10 years ago? I still own the CRT television I bought in 2006. $\endgroup$
    – Ben Norris
    Oct 27, 2012 at 14:58
  • $\begingroup$ @BenNorris It certainly feels like the old days even to me and I remember when digital watches used LEDs and you had to press a button to see the time. And portable computers had built in CRTs but took two people to carry them. $\endgroup$
    – matt_black
    Jan 16, 2014 at 22:55

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You should ask yourself: "For which application?". In fact there are different types of "phosphors" (most of them have no "Phosphorus" inside) for different applications and different compound were used during the evolution of CRT monitor. Some kind of phosphors may have advantages in terms of:

  • Efficiency of the luminescence induced.
  • Cheaper price.
  • Longer life.
  • Better color.
  • Shorter decay time.

Note however that in many application longer decay times are prefer because allow to the user to see transient signal one of this application is radar in this case is used the GB phosphors (it usually used the WTDS symbol to refer to a specific compound. In Phosphor Handbook by Shigeo Shionoya,William M. Yen,Hajime Yamamoto p. 607 you can find the relative compound in this case is $(Zn,Cd)S:Cu + (Ca,Mg)SiO_3:Ti)$) that has a time decay between 100 ms and 1 s.

If you are interested in RGB monitor and you want a list of the phosphors manly used. I've copied the the following table from Practical Applications of Phosphors by William M. Yen,Shigeo Shionoya,Hajime Yamamoto p. 232 showing how phosphors compound for every RGB channel changed during time.

\begin{array}{c c c c}\hline &Blue & Green & Red \\ \hline 1 & ZnS:Ag^{2+} & Zn_2SiO_4:Mn^{2+} & Zn_3(PO_4)_2:Mn^{2+}\\ 2 & ZnS:Ag^{2+} & (Zn,Cd)S:Ag & (Zn,Cd)S:Ag \\ 3& ZnS:Ag^{2+} & (Zn,Cd)S:Ag & YVO_4:Eu^{3+}\\ 4 & ZnS:Ag^{2+} & (Zn,Cd)S:Cu,Al & Y_2O_2S:Eu^{3+}or\space Y_2O_3:Eu^{3+} \\ Current & ZnS:Ag^{2+} & ZnS:Au,Cu,Al \space or \space ZnS:CU,Al &Y_2O_2S:Eu^{3+} \\ \hline \hline \end{array}

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I've read in a book that Europium is used in the red phosphors...

See more at this wikipedia page :

http://en.wikipedia.org/wiki/Phosphor

on this part of the webpage you will find info about used substances : http://en.wikipedia.org/wiki/Phosphor#Phosphor_degradation http://en.wikipedia.org/wiki/Phosphor#Materials

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  • $\begingroup$ I was hoping for a little more detain inside the answer. $\endgroup$
    – matt_black
    Jan 16, 2014 at 22:52

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