Calcium halophosphate

The Calcium Halophosphate Phosphors. Early fluorescent lamps used various combinations of naturally occurring fluorescent minerals. The development of the calcium halophosphate phosphor, Ca (P0 2(Cl, F) Sb ", Mn, in the 1940s was a significant breakthrough in fluorescent lighting (7). As is often the case in new phosphor discoveries, this phosphor was found accidentally while searching for phosphors for radar screens. 

Because it is stiU by far the most commonly used phosphor in fluorescent lamps, calcium halophosphate total production far exceeds that of all other phosphors put together, in excess of 1000 metric tons per year. 

For over 50 years the phosphors of choice for luminescent lighting have been based on activated calcium halophosphates, Ca3(PO )3X (where X = F, Cl), the usual activators being Sb " and Mn ". When Sb " is used as the dopant the phosphor is a very efficient blue emitter under 254 nm excitation, whilst Mn shows an orange... 

Figure 3.7 Schematic of emission spectra, (A) calcium halophosphate lamp and (B) tricolour...

This luminescence center is not detected in minerals yet, but is well known in synthetic phosphors, for example in halophosphates, which are closely related to hydroxyapatite (Blasse and Grabmaier 1994). The Sb doped calcium halophosphate is a very efficient blue-emitting phosphor under short wave 254 excitation (Fig. 5.56). When the halophosphate host lattice contains not only Sb, but also Mn, part of the energy absorbed by the Sb ions is transferred to Mn ", which shows an orange emission. By carefully adjusting the... 

Fig. 5.56. Emission and excitation spectra of calcium halophosphates A-Sb emission B-Mn emission C-warm-white halophosphate (Blasse and Grabmaier 1994)...

A fluorescent lamp is a glass tube filled with Hg vapor. The inner walls are coated with a phosphor (luminescent substance) consisting of calcium halophosphate (Ca5(P04)3F1 xClJ.) doped with Mn2+ and Sb3+. Hg atoms, promoted to an excited state by... 

Phosphors used in the production of fluorescent lamps are of the calcium halophosphate type, prepared by firing together calcium hydrogen phosphate, calcium carbonate and a lesser amount of calcium fluoride. The phosphor (0.25 g) can be dissolved in a small amount of concentrated... 

Davis TS, Kreidler ER, Parodi JA, Sotrles TF (1971) The luminescent properties of antimony in calcium halophosphates, J Ltrmines 4 48-62... 

Kingsley ID, Prener IS, Segall B (1965) Spectroscopy of (Mn04) in calcium halophosphates. Phys Rev A137 189-202... 

Ryan FM, Vodoklys FM (1971) The Optical Properties of Mn in Calcium halophosphate phosphors. JElectrchem Soc 118 1814-1819... 

Wachtel A (1958) The effect of impurities on the plaque brightness of a 3000 K calcium halophosphate phosphor. JElectrochem Soc 105 256-260... 

A serious drawback of this Mn phosphor is its poor maintenance in a lamp. It easily picks up mercury from the gas discharge and is liable to decompose under ultraviolet radiation. In addition beryllium is highly toxic [7], and nowadays not acceptable for application. In 1948, these phosphors were replaced by one phosphor with blue and orange emission, viz. Sb - and Mn -activated calcium halophosphate. 

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