DE2543491A1 - Europium activated lanthanide oxide phosphor prodn. - using flux contg. glass forming (fluoro)phosphate gives smooth grains of uniform size - Google Patents

Abstract

The prodn. of the phosphor, esp. a red phosphor for colour picture tubes, comprises calcining a mixt. of inorg. lanthanide and Eu cpds. in the presence of a flux. The flux used is based on a glass-forming phosphate (II) and another glass former (III) or a fluorophosphate and opt. (III). The phosphor is esp. suitable for the prodn. of phosphor screens by a paste process. Pref. (II) is a highly condensed phosphate and (III) is B2O3, AlF3, CaF3, LiF and/or BaPO3F. The flux components are made into a glass before mixing with (I) and calcining.

Description

"Procedure for making one with europium

activated rare earth metal oxide phosphors 5 The invention relates to a method for producing a rare earth oxide phosphor activated with europium, in particular a red phosphor for color cathode ray tubes, wherein a Mixture of inorganic compounds of rare earth metal and buropium in In the presence of a flux.

The manufacture of red-emitting phosphors based on of europium activated oxides of the elements yttrium, gadolinium, scandium or lanthanum is already known. Such phosphors are made by glowing the corresponding Oxalates as well as the commercially available oxides at temperatures between 600 and 16,000 C produced in a single or multi-stage annealing process. This also includes the use of fluxes, especially borax, boric acid, fluorides or barium chloride or also melting agents mixed from salts and oxides of alkali or alkaline earth metals, known.

However, the known method has the disadvantage that the location the color location, the brightness, the grain surface and the grain size of the phosphor can only be influenced with great difficulty with the aid of the said fluxes.

The invention was therefore based on the object of specifying a method the red fluorescent substances improved with regard to the specified properties required allowed to manufacture.

This object is achieved according to the invention in that a flux Us.wird, which consists essentially of a glass-forming phosphate and a further glass former or from a fluorophosphate and optionally another Glass sculptor consists.

The flux can be both commercially available rare earth oxides also the oxalates or those from oxalates at temperatures between 300 and 11,000 C, preferably 900 ° C, produced oxides are added. It is advantageous when using highly condensed phosphates in conjunction with others Glass formers, preferably B203, A1F3, CaF2 LiF, BaP03F, first Manufactures a glass at an elevated temperature, then finely grinds it and then mixed with the oxides or oxalates before the high temperature annealing process. The advantage This process consists in the fact that the oxides mixed with the powdered glass, z. B. with water or alcohol, made into a paste and without exposure to higher pressure Briquettes can be shaped so that no crucibles for the high-temperature annealing process more are required. Such crucibles can make the manufacturing process considerably more expensive, because their lifespan is usually very short due to the high temperatures and they consequently have to be replaced frequently.

Pluorophosphate (Na2 Po3 F) possibly in connection with B203, A1Ff, CaF24 LiF, BaP03F. If you set the flux can be commercial rare earth metal oxides, the phosphor can be manufactured in a single process step, thereby reducing the entire manufacturing process becomes very inexpensive.

Using the preferred exemplary embodiments described below The subject of the application is to be explained in more detail in relation to the invention.

Commercially available or obtained from oxalates are used as starting materials Rare earth oxides such as yttrium, scandium, gadolinium or lanthanum or mixtures these oxides are used, the europium serving as an activator.

This starting product becomes a flux in the form of a glass-forming agent Phosphate or a fluorophosphate added, the glass-forming phosphate It is essential to add another glass former, while the fluorophosphate can be used either alone or in conjunction with other glass formers. A glass can also be formed from these components at a higher temperature, which is then pulverized and mixed with the starting product. The melting agent is preferably added in such an amount that the melting agent concentration about 0.01-10 percent by weight, preferably 0.5-1.5 percent by weight.

The highly annealed and sintered product is then deagglomerated, then the deagglonized phosphor is passed over a 37-120 u gauze sieved, the excess water decanted off, the fluorescent kit with diluted, organic acid buffered nitric acid and 5 - 120 min., preferably 20-30 ml. treated. The concentration of nitric acid is 0.2-15%, preferably 8%, that of the organic acid 0.1-25%, preferably 10%. If an organic acid is also used, the attack is increased by the Very much reduced nitric acid.

Then the phosphor is filtered with demineralized Water washed, with alcohol, preferably isopropyl alcohol, rewashed, dried, then at 300 - 1100 ° C, preferably 900 ° C, for a time of 30 - 240 min., preferably 90 min., passivated.

The process according to the invention gives a phosphor of very even grain size and smooth grain surface, which is particularly suitable for processing is suitable in the L screen production by means of a slurry process.

Claims (5)

Patent claims oil ancestors for producing one activated with europium Rare earth metal oxide phosphor, in particular a red phosphor for color cathode ray tubes, being a mixture of inorganic compounds of rare earth metal and europium is annealed in the presence of a flux, characterized in that a Flux is used, which consists essentially of a glass-forming phosphate as well as a further glass former or from a fluorophosphate and optionally another glassmaker. 2. The method according to claim 1, characterized in that as glass-forming Phosphate a highly condensed phosphate is used. 3. The method according to claim 1 or claim 2, characterized in that that as a further glass former, a commercially available glass former, preferably B203, A1F3, CaF2, LiF, BaPO3F or a mixture of these glass formers is used. 4. The method according to any one of claims 1 to 3, characterized in that that from the raw materials used of the Flux initially a glass or glass mixture is formed, this glass or glass mixture is pulverized and added to the europium activated rare earth oxide, and this composition is subjected to at least one high temperature annealing process. 5. The method according to claim 4, characterized in that the from Europium activated rare earth oxide and flux formed composition before the high-temperature annealing process with water or an organic liquid, preferably isopropyl alcohol, made into a paste and then without the action of higher Print is formed into a briquette.