RU2401293C2 - Method of modifying anti-stokes luminiphors based on oxychlorides of rare-earth elements - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention describes a method of modifying anti-Stokes luminophors based on oxychlorides of rare-earth elements, involving treatment of a luminophor with low-melting glass with flow temperature of 560-600°C in amount of 7-20% of the weight of the initial luminophor at 560-600°C for 0.5-1 hour.

EFFECT: obtaining modified anti-Stokes luminophor with high output and high moisture resistance with retention of high level of luminous intensity during infrared excitation.

9 ex

Description

The invention relates to a technology for the modification of phosphors, namely anti-Stokes phosphor based on REE oxychloride.

The invention is aimed at solving the problem of obtaining an anti-Stokes phosphor based on REE oxychloride with high moisture resistance.

A known method of modifying the surface of phosphors based on oxyhalides and oxychalcogenides of REEs by treating them with inorganic silicon-containing compounds from aqueous solutions: solutions of potassium silicate and Group II metal compounds, followed by calcining the treated product in air at 400-800 ° C for 0.5-3 hours (US Patent No. 4690832, 1987, CL 09/11/75).

Known methods for modifying the surface of phosphors based on oxyhalides and oxychalcogenides of REE by treating them with organosilicon compounds: solutions of organic silanes, including their chlorine derivatives (Japanese Patent No. 53-17555, 1978, CL 09/11); 0.5-5% aqueous solution of alkali metal organosiliconate, followed by separation of the phosphor from the solution, drying, sieving and annealing at a temperature of 450-500 ° C in air (USSR Author's Certificate No. 675953, 1977, class C09K 11/54) ; 0.45-3.8% solution of γ-aminopropyltriethoxysilane, followed by drying and heat treatment of the resulting product in a CO ₂ atmosphere at P = 0.3-0.5 atm in 2 stages: in the first stage at 350-530 ° C for 1 -2 hours, and in the second stage at 800-1000 ° C for 1-2 hours (USSR Author's Certificate No. 1385599, 1986, class C09K 11/84).

A common disadvantage of these methods that impede their practical use in the production of phosphors based on REE oxyhalides is the low moisture resistance of the obtained phosphor.

A known method of modifying phosphors based on rare earth oxychlorides, which consists in processing the phosphors by grinding in an aqueous solution of γ-aminopropyltriethoxysilane 0.6-0.7% concentration in the presence of 0.3-0.5% sodium salt of carboxymethyl cellulose at T : W = 1: 10 for 0.5-0.7 hours and the resulting suspension is dispersed through a pneumatic nozzle, and the phosphor after separation from the suspension is additionally treated with an 8-12% aqueous solution of aminopropyltriethoxysilane in the presence of ionic khnostno-active substance - 100% sodium salt of di-2-ethylhexyl ether sulfosuccinic acid, taken in an amount of 30-40% by weight of the original phosphor (Author's certificate No. 1720270, 1989, CL 09/11).

The main disadvantage of this method is the low yield of the finished phosphor 60-70%, which significantly increases the cost of the already expensive product, as well as low moisture resistance. An analysis of experimental tests revealed that this drawback, associated with a low yield of the product, is fundamentally inherent in this method and is associated with the polymerization processes used for processing organic compounds, which lead to agglomeration of individual phosphor particles into large conglomerates of size unsuitable for practical use. more than 100 microns. Grinding such a phosphor even in “mild” conditions leads to the destruction of the integrity of the protective organic coating and a significant decrease in the moisture resistance of the phosphor.

A technical solution is known in which a vitreous coating is applied to the surface of a phosphor based on zinc and zinc sulfides — cadmium (Application of Germany No. 2747509, 1979, class C09K 11/02). For this, the phosphor powder is mixed with an alcoholate solution containing 50-90 wt.% SiO ₂ , 10-50 wt.% B ₂ O or 0-20 wt.% MgO or CaO, 0-20 wt.% Li ₂ O or - Na ₂ O. The resulting mixture is transferred to a gel, for which it is left for several hours in a humid atmosphere. Then the gel is calcined at a temperature of 200-800 ° C. After processing, phosphor powders are used to produce luminescent varnishes and plastics, in the manufacture of ceramic tiles and enameled products. The main disadvantage of this method is the low moisture resistance of the obtained phosphor.

The closest in technical essence and the achieved result to the claimed solution is the prototype method for modifying the surface of phosphors based on REE oxychloride by treating it with a glass-containing component, namely liquid glass (Japan Application No. 63-182392, 1988, class C09K 11/08). According to this method, a phosphor based on terbium-activated lanthanum oxychloride is initially thoroughly washed with clean water. Then, an aqueous solution of liquid glass K ₂ O · 3SiO ₂ and Al ₂ (SO ₄ ) ₃ in predetermined concentrations is subsequently added with stirring. A KOH solution of a given concentration is added and the resulting mixture is thoroughly mixed for the complete interaction of water glass and Al ₂ (SO ₄ ) ₃ . The treated phosphor is dried at a temperature of 120 ° C and sieved. As a result of the operations obtained, a phosphor with a surface coating of Al ₂ SiO ₅ in the ratio of 0.05-6.6 wt. parts of Al ₂ SiO ₅ per 100 wt. parts of the phosphor.

According to the data in the prototype, the processed phosphor has a high radiation resistance at high current densities in projection CRTs. As our tests showed, the main disadvantage of the described method is the low moisture resistance of the obtained oxychloride phosphor, which is associated with the inability to provide a continuous surface coating of the compound Al ₂ SiO ₅ .

Thus, from the analysis of the patent literature it follows that the main drawback of the known technical solutions is the absence of a continuous and strong protective coating on the surface of the phosphor particles, which, in comparison with the initial phosphor, has high thermal and chemical resistance and is sufficiently transparent to exciting and emitted light. A fundamental solution to the problem of increasing the moisture resistance of phosphors can be mixing particles of finely dispersed fusible glass (average particle size of 1 μm or less) with phosphor grains (average size of 5-10 μm), which ensures their uniform distribution over the surface of the latter, and calcination at a temperature of equal to the spreading temperature of the glass or slightly exceeding it.

The technical result of the invention is to increase the moisture resistance of phosphors based on REE oxychlorides while ensuring a high yield of the finished product.

This technical result is achieved by the fact that in the inventive method for modifying anti-Stokes phosphors based on REE oxychlorides, comprising treating the phosphor with a silicon-containing compound and sifting it, according to the present technical solution, the processing of oxychloride is carried out in the presence of a finely dispersed silicon-containing low-melting compound with a spreading temperature of 560 ± 10 ° C in the amount of 7-20% by weight of the initial phosphor in air at a temperature of 560-600 ° C for 0.5-1 hours. To modify the phosphor using fusible glass of the following composition, wt.%:

SiO ₂ 10.5-11.5 B ₂ O ₃ 14.6-16.6 Al ₂ O ₃ 1.1-2.7 PbO rest,

мкм.with medium particle size

microns.

In relation to the prototype, the claimed invention has the following distinctive features: the processing of REE oxychloride activated by erbium is carried out in the presence of a finely dispersed silicon-containing fusible compound taken in an amount of 7-20% by weight of the initial phosphor at a temperature of 560-600 ° C for 0.5 -1 hours, and as a modifier use glass with a spreading temperature of 560 ± 10 ° C, with the following ratios of components, wt.%:

SiO ₂ 10.5-11.5 B ₂ O ₃ 14.6-16.6 Al ₂ O ₃ 1.17-2.7 PbO rest.

Modified by the proposed method, anti-Stokes phosphor based on REE oxychloride has high moisture resistance while maintaining a high level of luminous intensity upon IR excitation. In addition, the proposed method provides an increased yield of the finished product.

Between the distinguishing features and the technical result of the invention there is the following causal relationship: the processing of REE oxychloride activated by erbium is carried out in the presence of a finely dispersed silicon-containing fusible compound taken in the amount of 7-20% by weight of the initial phosphor at a temperature of 560-600 ° C for 0 , 5-1 hours, and glass of the claimed composition with a spreading temperature of 560 ± 10 ° C, which provides increased moisture resistance and a high yield of the finished product, is used as a modifier while maintaining a high level of light intensity. The choice of boundary values of the parameters is due to the fact that a decrease in the number of fusible glass in the charge, the temperature and duration of the calcination of the charge, as well as the number of glass components to values lower than those indicated in the claims, is impractical, since the necessary continuity of the inorganic film on the phosphor surface is not provided and some physico-chemical properties of the coating (spreading temperature, coefficient of thermal expansion). These changes adversely affect the moisture resistance of the phosphor, which excludes the possibility of its practical use.

An increase in the number of fusible glass in the charge, the temperature and duration of annealing, as well as the number of glass components to values greater than those indicated in the claims, is also impractical, since due to the significant thickness of the inorganic coating, a significant decrease in the relative brightness of the luminophore glow is observed. In addition, it is economically disadvantageous.

Exposure of hydrolytically unstable compounds, such as phosphors based on REE oxyhalides, in a humid atmosphere for several days due to their partial hydrolysis leads to a significant decrease in the intensity of luminescence and makes the phosphors unsuitable for practical use. Thus, the proposed set of features is a necessary and sufficient condition for achieving this goal.

The essence of the proposed method for modifying anti-Stokes phosphors based on REE oxyhalides is to mix particles of finely dispersed fusible glass (average particle size 1 μm or less) with phosphor grains (average size 5-10 μm), which ensures their uniform distribution over the surface of the latter, and calcination at a temperature equal to the glass spreading temperature or slightly above it, leads to the formation of an almost continuous and durable protective coating, which, in comparison with and similar phosphor with enhanced chemical and thermal resistance.

The advantage of the proposed method is the exclusion of the use of aqueous solutions of silicon-containing compounds, which ensures the stability of the chemical composition and luminescent properties of the product during its processing.

The thickness of the protective coatings can be controlled by changing the glass content in the initial charge and is selected so that while maintaining a high yield of the product, there is no deterioration in the intensity of luminescence and moisture resistance.

The set of essential features characterizing the essence of the claimed invention is not known from the prior art, which allows us to conclude that the invention meets the criterion of "novelty."

According to the authors, the essence of the claimed invention does not follow explicitly from the prior art for a specialist, since the above effect on the obtained technical result is not revealed from it - a new property of the object - a set of features that distinguish the claimed invention from the prototype, which allows us to conclude about it compliance with the criterion of "inventive step".

The set of essential features characterizing the essence of the invention, in principle, can be repeatedly used in the technology of modifying anti-Stokes phosphors based on REE oxyhalides, which allows us to conclude that the invention meets the criterion of "industrial applicability".

The inventive method of modifying anti-Stokes phosphors based on REE oxyhalides using the entire set of features is described by examples.

Example 1 (prototype)

A portion of a phosphor based on ytterbium oxychloride activated by erbium ions, for example, Yb _0.96 Er _0.04 OCI or (Yb _0.69 Yb _0.30 Er _0.01 ) ₃ OCI ₇ , is pre-washed with pure water. Then, aqueous solutions of water glass (K ₂ O · 3SiO ₂ ) and Al ₂ (SO ₄ ) _{3 of} predetermined concentrations are added successively with stirring. A KOH solution of a given concentration is added and the mixture is stirred for the interaction of water glass and Al ₂ (SO ₄ ) ₃ on the surface of the phosphor. The processed phosphor is dried at a temperature of 120 ° C and sieved through a No. 76 sieve. Get a phosphor with a surface coating of Al ₂ SiO ₅ in the ratio of 0.05-6.6 wt. parts of Al ₂ SiO ₅ per 100 wt. parts of the phosphor.

The moisture resistance of the obtained phosphor is determined by the following method: the treated phosphor is rubbed in stainless steel cuvettes and the relative brightness of the luminescence when excited by infrared radiation of an arsenide-gallium LED AL-107B is measured. Then the cuvette with the phosphor is placed in a climatic chamber, providing at a constant temperature (25 ± 2 ° C) a relative humidity of 98%. After exposure to the climate chamber for 5 days, the cuvette with the phosphor is removed from the chamber and the relative brightness of the glow is measured.

The moisture resistance of the phosphor is determined by the formula:

Moisture resistance = V _t / V _ref × 100%,

where B _ref and B _t are the values of the relative brightness of the phosphor glow before and after climatic tests, respectively.

The moisture resistance of the obtained product is 35%, the relative brightness of 100%, the yield of the finished product 89%.

Example 2

To 10 g of an anti-Stokes phosphor based on REE oxychloride, for example, Yb _0.96 Er _0.04 OCI, 0.7 g of low-melting glass composition is added: SiO ₂ - 10.5 wt.%, B ₂ O ₃ - 15.6 wt. %, Al ₂ O ₃ - 2.7 wt.%, PbO - 71.2 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm.

The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 580 ° C for 1 hour. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 367%, the yield of the finished product is 96.5%.

Example 3

To 10 g of the anti-Stokes phosphor based on REE oxychloride, for example, to Yb _0.96 Er _0.04 OCI, 1.35 g of low-melting glass composition is added: SiO ₂ - 11.5 wt.%, B ₂ O ₃ -14.6 wt. %, Al ₂ O ₃ - 1.8 wt.%, PbO - 72.1 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm. The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 560 ° C for 0.5 hours. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 348%, the yield of the finished product 95.0%.

Example 4

To 10 g of an anti-Stokes phosphor based on REE oxychloride, for example, to Yb _0.96 Er _0.04 OCI, 2 g of fusible glass of the composition are added: SiO ₂ - 11 wt.%, B ₂ O ₃ - 16.6 wt.%, Al ₂ O ₃ - 1.1 wt.%, PbO - 71.4 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm.

The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 600 ° C for 0.75 hours. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 341%, the yield of the finished product is 94.4%.

Example 5

To 10 g of an anti-Stokes phosphor based on REE oxychloride, for example, to Yb _0.96 Er _0.04 OCI, 0.7 g of low-melting glass composition is added: SiO ₂ - 10.5 wt.%, B ₂ O ₃ - 14.6 wt. %, Al ₂ O ₃ - 1.8 wt.%, PbO - 73.1 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm.

The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 560 ° C for 0.5 hours. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 358%, the yield of the finished product is 96.8%.

Example 6

To 10 g of an anti-Stokes phosphor based on REE oxychloride, for example, to Yb _0.96 Er _0.04 OCI, 2 g of fusible glass of the composition are added: SiO ₂ - 11.5 wt.%, B ₂ O ₃ - 16.6 wt.% , Al ₂ O ₃ - 2.7 wt.%, PbO - 69.2 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm.

The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 600 ° C for 1 hour. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 329%, the yield of the finished product is 90%.

Example 7

To 10 g of an anti-Stokes phosphor based on REE oxychloride, for example, to Yb _0.96 Er _0.04 OCI, 0.7 g of low-melting glass composition is added: SiO ₂ - 10.5 wt.%, B ₂ O ₃ - 14.6 wt. %, Al ₂ O ₃ - 1.8 wt.%, PbO - 73.1 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm.

The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 580 ° C for 0.75 hours. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 358%, the yield of the finished product is 96%.

Example 8

To 10 g of an anti-Stokes phosphor based on REE oxychloride, for example, to Yb _0.96 Er _0.04 OCI, 2.2 g of fusible glass of the composition are added: SiO ₂ - 11.0 wt.%, B ₂ O ₃ - 16.6 wt. Wt.%, Al ₂ O ₃ - 2.7 wt.%, PbO - 69.7 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm.

The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 620 ° C for 1.1 hours. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 275%, the yield of the finished product is 87%.

Example 9

To 10 g of an anti-Stokes phosphor based on REE oxychloride, for example, to (Yb _0.96 Er _0.04 OCI) ₃ OCI ₇ , add 1.0 g of low-melting glass composition: SiO ₂ - 11.0 wt.%, B ₂ O ₃ - 16.6 wt.%, Al ₂ O ₃ - 1.8 wt.%, PbO - 70.6 wt.%, Which is pre-crushed sequentially in ball and bead mills to a particle size of ≤1 μm.

The resulting mixture is placed in a quartz crucible and calcined in air at a temperature of 580 ° C for 0.75 hours. The phosphor is cooled, sieved through a No. 76 sieve.

The moisture resistance of the obtained product is 100%, the relative brightness of 615%, the yield of the finished product is 97%.

Thus, the inventive method of modifying anti-Stokes phosphors based on REE oxyhalides provides an increase in moisture resistance while maintaining a high level of luminous intensity and an increased yield of the product.

The inventive method provides the introduction of new technology to reduce the cost of the finished product, to simplify the process of obtaining anti-Stokes phosphor with the necessary parameters, and also to protect nature by reducing wash water and waste.

Claims (2)

1. A method of modifying anti-Stokes phosphors based on rare-earth oxychlorides, comprising treating the phosphor with a silicon-containing compound and sifting it, characterized in that the processing of the oxychloride is carried out using low-melting glass as a silicon-containing compound with a spreading temperature of 560-600 ° C in an amount of 7-20% by weight of the initial phosphor at a temperature of 560-600 ° C for 0.5-1 hours 2. The method according to claim 1, characterized in that as a low-melting glass using glass containing, wt.%:
SiO ₂ 10.5-11.5 B ₂ O ₃ 14.6-16.6 Al ₂ O ₃ 1.1-2.7 Pbo rest