FIRST GENERATION PHOSPHORS
The fluorescent tubes used in the past, are phosphors of Zinc Beryllium Silicate – the first material to create white light with reasonable quality. However, the efficiency of tubes using these materials was just 35 lumens per watt.
THE CIE COLOURTRIANGLE
SECOND GENERATION THE HALOPHOSPHATES
Investigation for better lamp efficacy resulted in the so called Halophosphate’ tubes. The neontubes where coated with Calcium Halophosphate, (generally known as ‘Halophosphate’ tubes). The most common tubes on the global lighting market. The lamp efficacy is approx. 60 – 75 lm/W.
Although, such tubes have a low initial purchase cost. This rapidly offset by the increase of electrical power consumption, which required to generate a given amount of light. Halophosphate tubes will shortly be phased out under EU legislation, this to enforce the adoption of other and more efficient fluorescent phosphor materials.
THIRD GENERATION THE TRIPHOSPHORS
New materials were mixed in order to create a better efficiency of the neon tubes. For this reason the modern family of Tri-phosphor lamps was born. One of each of the following colours: blue, green, and red fluorescent components are generally employed in modern tri-phosphor tubes.
The basic colours are:
- Blue: SrCaBaMg
Chloroapatite chemical composition (Sr,Ca,Ba,Mg)5(PO4)3Cl : Eu2+
- Green: Calcium Tungstate (CAT)
chemical composition Ce0.65Tb0.35MgAl11O19
- Red: Yttrium Oxide (YOX) chemical composition Y2O3 : Eu3+
An unexpected advantage of these deeply saturated colored phosphors are their astonishing efficiency of converting UV into visible light. As a result lamp efficacy is boosted to levels of around 80 – 95 lm/W.
The spectra of common tube colours are shown in the diagrams below, and their colour points are indicated on the CIE chromaticity triangle.