DD226899A1 - METHOD FOR PRODUCING A FLUORATE - Google Patents

Abstract

The invention relates to a process for the preparation of a phosphor based on blue-emitting barium europium magnesium aluminate having a hexagonal crystal structure for use in single and multi-component fluorescent lamps. The object of the invention is to produce a phosphor more cost-effective, with which an increase in quality of fluorescent lamps is guaranteed. The invention has for its object to develop a process for the production of barium europium magnesium aluminate phosphor having a defined grain size distribution, are saved in the elaborate intermediates and the post-treatment of the phosphor. According to the invention, this object is achieved by reacting Al 2 O 3 in the solid state reaction whose grain size distribution is adjusted by varying the precipitation temperature of the Al (OH) 3 and subsequent calcination to g or α-Al 2 O 3 and / or by classification, wherein the influencing of the grain size distribution the phosphor is achieved via the particle size distribution of the g- or a-Al 2 O 3 used and by varying the annealing temperature of the phosphor.

Description

Title of the invention

Process for the preparation of a phosphor

Field of application of the invention

The invention relates to a process for the preparation of a blue-emitting barium-europium-magnesium aluminate-based luminophore having a hexagonal crystal structure which is used as a single component or as a constituent of a multicomponent mixture in discharge lamps for illumination purposes, phototherapy and for influencing photochemical processes.

Characteristic of the known technical solution

It is known that by conventional grinding and subsequent classification methods, for example by sieving, sifting and sedimentation, phosphor powders which have been produced by conventional solid-state reaction and have a broad particle size distribution are decomposed into discrete particle fractions. As a result, the grain size ranges of 2-20 are reached, which are common in fluorescent lamps and optimal in terms of light output, adhesion, coating weight and appearance of the layer.

The disadvantage of the method is that additional processing steps are necessary with simultaneous reduction of the yield by this type of treatment of the phosphors. In addition, in most cases, negative effects on the important for the luminescence process surface of the crystallites and thus on the quality of the phosphors.

The process typically according to DE-OS 2,353,943 and U.S. Patent No. 4,161,457 used for the production of aluminate phosphors using non-uniform Al ₃ O _3, and melting agents have the mentioned disadvantages, since the desired particle size of the phosphors not reproducible can be obtained.

The disadvantage of the procedure described in DD-PS 207 213 for the preparation of aluminate phosphors with uniform particle size and particle shape is that the preparation of C ^ -Al ₂ O ₃ via Jf ^ -Al ₂ O ₃ from (NH ₄ ) Al (SO ₄ J _2, 12 H ₂ O in several processing steps by gas-phase transport reaction halogen-containing, the conversion reaction-initiating compounds, such as NH.Cl require .This means higher production and energy costs, a higher environmental impact by the release of gaseous NH ₄ Cl or HCl and SO ₃ or SO ₂ connected and also consuming washing operations to remove the Cl "- and

2-SO _4- ions necessary.

Object of the invention »

The object of the invention is to produce a phosphor more cost-effectively, with which an increase in quality of fluorescent lamps is guaranteed.

Explanation of the essence of the invention

The invention is based on the object to develop a process for the preparation of barium europium magnesium aluminate phosphor having a defined particle size distribution, in which expensive intermediates and the post-treatment of the phosphor are saved.

According to the invention the object is achieved in that it is assumed that a mixture of carbonates, fluorides and / or oxides of the elements barium, europium, magnesium and aluminum and this is reacted in a solid state reaction to a Bariumeuropiummagnesiumaluminat phosphor having a hexagonal crystal structure. It should be noted that the particle size distribution of the used jj "- or oO-AlJ3 ~ is below the particle size distribution, which should have the phosphor.

The corresponding particle size distribution of the Al ₂ O ₃ can be obtained by conventional grinding and subsequent classification methods, such as sieving, sifting, sedimentation, among others. This procedure in this processing step shows no negative effects on the subsequent representation of the phosphor · Particularly efficient way to set the grain size distribution of Al ₂ ⁰ O on the precipitation temperature in the representation of Al (OH) ₃ in aqueous solution. After several washes, the Al (OH) ₃ is converted by combustion into <f- or Od-Al ₂ O ₃ with a defined particle size distribution. The investigations on the influence of the precipitation temperature have shown that in the temperature range of 10 ⁰ C -

 2 ° 3

100 C the maximum of the grain size distribution of Al ^ O "can be varied between 0.1 - 60 UTi.

It has also been demonstrated that there is a shift in the areas of maximum grain size between the starting ^ or οό- Al ₂ O ₃ starting product and the phosphors prepared therefrom * This maximum shift is between 3-15 / μm depending on the structure of the grain size distribution of the Al O ₃ . It was also found that the variation of the annealing temperature of the phosphor between 1000 - 2000 ⁰ C causes a change in the maximum of the particle size distribution of the phosphor in the range of 1-60 / To ·

The barium-europium-magnesium aluminates having a hexagonal crystal structure produced at lower cost by the process according to the invention have high efficiency, high stability, the required luminescence properties and the desired grain size distribution for the further processing process as lamp luminescent material.

embodiments

The invention will be explained below with reference to three embodiments.

Example 1:

The highly purified starting materials, such as · 12.321 g BaCO ,,, 4.392 g MgF _2, Al ₃ O ₃ 41.069 g, and 1.418 g Eu ₂ O ₃ are intensively ground in a mortar and a Sinterkorundtiegel in a Sinterkorundrohr in N ₂ / H ₂ gas flow annealed at an annealing temperature of 1200 ⁰ C for 1 h. When a ^ - or O ^ - ^Al 2 ° 3 ^{with a grain size} range between ^{2.5-5 /} μm is used, which was generated by classification, an aluminate phosphor with a maximum grain size range of between ^{7 and 12} μm is formed.

Example 2:

Is used according to the method described in Example 1, a ο - or o ^ -Al ₂ O ₃ , which is formed from an Al (OH) ₃ shown at a precipitation temperature of 38 ⁰ C followed by calcination to Al ₂ O ₃ and a Grain spectrum with a maximum between 5-10, um, results in an aluminate phosphor having a maximum grain size range between 10 - 20, to.

Example 3:

Is by the process described in Example 1, an annealing temperature of 1200 ⁰ C selected, an aluminate phosphor is produced with an area of maximum grain size of between 8-13 in order, while at an annealing temperature of 1500 ⁰ C, a region of maximum grain size of between 20 - 33, to occur.

Claims (1)

invention claim 1. A process for the preparation of blue-emitting barium europium magnesium aluminate phosphor having a defined particle size distribution by solid state reaction, characterized in that in the solid state reaction Al ^ O «is implemented whose particle size distribution by varying the precipitation temperature of the Al (OH) ₃ and subsequent calcination to ^ £ <> - Al ₂ O ₃ and / or is adjusted by classifying, wherein the influencing of the grain size distribution of the phosphor is achieved by the particle size distribution of the used ^ - or $ -A -Al ₂ O ₃ and by varying the annealing temperature of the phosphor.