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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. [Pg.287]

Fig. 5. The emission spectmm of a typical cool white halophosphate phosphor showing the emission band around 480 nm and the emission... Fig. 5. The emission spectmm of a typical cool white halophosphate phosphor showing the emission band around 480 nm and the emission...
After firing, the powder is washed in water typically with a small amount of complexing agent such as ethylenediarninetetraacetic acid (EDTA), sodium EDTA, or a weak acid such as citric acid to remove the excess chloride, volatile antimony oxychlorides which have recondensed on the phosphor during cooling, and manganese compounds which are not incorporated in the halophosphate lattice. The powder is then ready for suspension. [Pg.288]

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. [Pg.288]

The cost of rare-earth phosphors in fluorescent lamps is often reduced by double coating the lamps. The rare-earth phosphor blend is coated over a base layer of the inexpensive halophosphate phosphor (Fig. 9). In this configuration it absorbs a disproportionate amount of the uv discharge. For example, about 70% of the uv is absorbed in the inner coating with only one layer of triphosphor particles on the inside. [Pg.289]

Fig. 9. A modem fluorescent lamp coating including a conductive layer of Sn02 F, then a protective coating of finely divided alumina, followed by the inexpensive halophosphate phosphor, and finally a thin layer of the triphosphor rare-earth blend. Fig. 9. A modem fluorescent lamp coating including a conductive layer of Sn02 F, then a protective coating of finely divided alumina, followed by the inexpensive halophosphate phosphor, and finally a thin layer of the triphosphor rare-earth blend.
Since there are no volatile components this halophosphate phosphor is prepared with close to the stoichiometric amounts of SrHPO, SrCO, CaCO, BaCO, SrCl2, or NH Cl and EU2O2. The blend is fired under an atmosphere containing 1—2% hydrogen at 1100°C. A small excess of chloride provides some fluxing action and gives weU-formed crystals of apatite. The chlorapatites are dimorphous one modification is hexagonal and the other monoclinic. [Pg.291]

In volume terms the most important class of fire retardants are the phosphates. Tritolyl phosphate and trixylyl phosphate are widely used plasticisers which more or less maintain the fire-retarding characteristics of PVC (unlike the phthalates, which reduce the flame resistance of PVC products). Better results are, however, sometimes obtained using halophosphates such as tri(chloroethyl) phosphate, particularly when used in conjunction with antimony oxide, triphenyl stibine or antimony oxychloride. [Pg.148]

The smaller electrostatic charge of the halophosphates, i.e. 2 and 1 resp., compared with the triple charge in [PO ] , gives rise to a certain anisotropy of the bonding system, which especially in the dihalophosphates causes the formation of bonds with evidently homopolar character. This is certainly one of the reasons for their stmctural variety. [Pg.52]

The most intensely investigated of all halophosphates are certainly the dichlorophosphates, about which extensive crystallographic and spectroscopic data exist. This might be brought into connection with the fact, that for the preparation of the dichlorophosphates there is an especially rich variety of methods for synthesis at hand. On the... [Pg.61]

The main investigation methods, to give information about structure and bonding in the halophosphates, are vibrational and NMR spectroscopy, which give a fairly complete picture. Up to now, X-ray studies are restricted to a few examples only indirectly they are of some importance in the discussion, especially of infrared and Raman spectra however. In some cases indirect information has been instructive, e.g. Mossbauer spectra of iron and tin halophosphates, so that these measurement shall be mentioned too. [Pg.68]

Up to know crystal structure analyses have been made with difluorophosphates, monofluorophosphates and dichlorophosphates only. Table 3 gives the bond lengths and bond angles in these three halophosphates. [Pg.68]

In the undisturbed state, the halophosphates can be classified by the following point groups (vibrational species in brackets) ... [Pg.70]

Table 5 shows the most important NMR data of halophosphates. In the species containing fluorine, apart from the chemical shifts of the P-spectra, the F-spectra and the coupling constants Jpp are available for the discussion of bonding. The importance of NMR spectroscopy for purity control, for equilibrium measurement, as kinetical method in the investigation of reaction processes and for the identification of unstable compounds shall not be discussed here, though these apphcations are of great importance for the halophosphates too. [Pg.76]

Structural and Bonding Aspects in Phosphorus Chemistry Table 6. Mossbauer spectra of halophosphates of tin and " tron... [Pg.79]

Recently the halophosphates [Ti0Cl(P02Cl2) POCl3] (i76), Cr(P02p2)3, K2lM02(P02F2)4l (M = Cr, Mo, W) (117) and several tetramethylstibonium dihalophosphates (118) have been prepared and characterised by vibrational spectroscopy. [Pg.82]

Sr2P207 Sn2+ CaHP04, SrHP04, SnO, (NH4)2HP04, NH4C1 Blue-emitting phosphor used in blends with halophosphate phosphors for specific lamp colors... [Pg.699]

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... [Pg.166]

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

See other pages where Halophosphate is mentioned: [Pg.152]    [Pg.462]    [Pg.287]    [Pg.287]    [Pg.287]    [Pg.288]    [Pg.288]    [Pg.288]    [Pg.288]    [Pg.289]    [Pg.290]    [Pg.291]    [Pg.291]    [Pg.371]    [Pg.148]    [Pg.197]    [Pg.197]    [Pg.52]    [Pg.68]    [Pg.71]    [Pg.71]    [Pg.72]    [Pg.78]    [Pg.79]    [Pg.699]    [Pg.483]    [Pg.159]    [Pg.167]   
See also in sourсe #XX -- [ Pg.197 ]




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