NL9102141A - ANTIMONIC AND MANGANA ACTIVATED LUMINESCENT CALCIUMBARIUM FLUORAPATITE EQUIPMENT. - Google Patents

Description

Luminescent calcium-barium fluorapatite material activated with antimony and manganese

Background of the prior art

This invention relates to luminescent alkaline earth metal halophosphate materials (phosphors). Such luminescent materials are described in U.S. Patent 2,488,733. The invention particularly relates to calcium halophosphate activated with antimony and manganese. Such a luminescent material is widely used in fluorescent lamps.

The halogen used in such luminescent materials is primarily fluoride, although a small amount of chloride is often also used because chloride gives a desirable increase in red emission.

Summary of the invention

It is an object of this invention to eliminate the use of chloride in the manufacture of luminescent halophosphate materials so as to reduce the amount of flue gas dust generated in the process of making the luminescent materials. Much of the chloride is lost during the reaction to make the luminescent materials, due to the formation of Sb405Cl2 which volatilizes and collects as a flue gas dust.

We have found that when controlling the composition of a luminescent material within narrow limits, a replacement of calcium with barium can be used to vary the trichromatic coordinates in the same direction as happens with chloride. Surprisingly, the trichromatic coordinates do not vary along a straight line, they vary along a curve that increases the x coordinate and decreases the y coordinate to a certain concentration of barium.

A luminescent calcium barium fluorapatite material according to this invention has the following formula:

Ca4,731-aBaaMnbSbc (P04) 3Fl-c ° c where 0 <a <0.3 or 3.1 <a <4.731 b is about 0.0952 c is about 0.03

Description of the drawing

Fig. 1 shows the effect of composition changes on the color coordinates of a luminescent halophosphate material, taken from page 44 of "Fluorescent Lamp Phosphors" by Keith H. Butler, Pennsylvania State University Press, 1980.

Fig. 2 shows the color shift of a luminescent material of this invention as more barium is absorbed.

Preferred embodiment

Samples of various manganese and antimony-activated calcium fluorapatite, calcium-barium fluorapatite and barium fluorapatite materials are prepared by the general procedure disclosed in U.S. Patent No. 2,965,786. For the manganese and antimony-activated calcium fluorapatite, the following starting materials used:

CaHPO4 3,000 mol

CaCO3 1,265 mol

CaF2 0.466 mol

Sb2 O3 0.0155 mol

MnCO 3 0.0952 mol

For those samples in which barium is used to replace part or all of the calcium, the replacement can be done by using BaHPO4, BaF2 or BaCO3 in place of the corresponding amount of CaHPO4, CaF2 or CaCO3. Thus, luminescent materials are prepared with the following formula: ^ 4.731-3 ^ 0 ^ 0.0952 ^ 0.03 (PO4) 3F0.932 ° 0.03

The starting materials are mixed together by grinding the mixture in acetone in a ball mill for half an hour. The resulting mixture is air-dried before being fired at 1150 ° C according to the general procedure disclosed in U.S. Patent No. 2,965,786.

The CIE color coordinates for a number of materials in which a is varied in the above formula are listed in Table A.

Table A

The color (chromatic coordinates) of these luminescent compositions are plotted in Fig. 2. As can be seen, the color shifts to red with x increasing and y decreasing from A, initially until a equals approximately 0, 4 moles (corresponding to a replacement of the cation content for about 8.5% by barium). When a is increased to 1.0 mol (point D in Figure 2; about 21% replacement of cations with barium), the color of this composition corresponds to a higher x and about constant y with respect to point A.

At higher a, the emission of the luminescent material gradually shifts to the greener barium fluorapatite (point H).

Thus, the change in the emission color (chromaticity) by increasing the replacement of calcium by barium in the calcium fluorapatite does not proceed in a straight line (between points A and H in Figure 2) as would be expected. Interestingly, point G does lie on this predicted straight line.

At a low "a" between 0.0 and about 0.3, a solid solution rich in calcium of luminescent material is formed. This solid solution of luminescent material gives a red shift in the emission color (chromaticity) (higher x, lower y compared to pure luminescent calcium fluorapatite material). At a high "a" between about 3 and 4,731, a solid solution of luminescent material rich in barium is formed. This solid solution of a high barium luminescent composition gives a greener emission compared to the pure luminescent calcium fluorapatite material, but a shift to red relative to the pure luminescent barium fluorapatite material.

For an "a" between about 0.3 and 3, the composition does not include a solid solution but consists of two immiscible phases. One of these is a calcium fluorapatite phase in which there has been little replacement of calcium by barium. The other is a barium fluorine-patite phase in which there is a slight replacement of barium by calcium.

Claims (2)

1. Luminescent calcium barium apatite material having the following composition: ^ 4.731-38¾14¾81 ^ (PO4) 3F1-c ° c where o <a <0.3 or 3.2 <a <4.731 b is about 0.0952 c about 0, 03 is A method for increasing x and decreasing y along a curved line in the CIE color (chromaticity) diagram of an antimony and manganese activated luminescent calcium fluorapatite material, comprising the steps of preparing a luminescent material of the formula of ^ 4.731-8 ^ 3 ^ 0.0952 ^ 0.03 (PO4) 3F0.932 ° 0.03 and replacing calcium in this formula with barium in an amount "a" from 0 to 1,899.