RU2031918C1 - Self-activated luminescent with radiation at the range 0,5-0,7 mcm, and a method of its preparing - Google Patents

Abstract

FIELD: luminescence. SUBSTANCE: self-activated luminescent with radiation at the range 0.5-0.7 mcm is barium tungstenfluoride of the formula BaWF₆. Synthesis: interaction of barium oxide, hydroxide or carbonate and tungsten oxide taken at the equimolar ratio in concentrated hydrofluoric acid in autoclave at 160-260 C for 2-4 h. Brightness luminance of prepared luminescent is more significantly as compared with that prepared on the basis of magnesium tungstate. EFFECT: enhanced quality of luminescent. 3 cl, 2 dwg, 2 tbl

Description

 The invention relates to quantum optics and can be used in lighting, medical and electronic instrumentation.

Known phosphors with radiation in the spectral range of 0.5-0.7 μm, which are excited by cathode rays described by the formulas Y ₂ O ₂ S: Tb, Zn ₂ SiO ₄ : Mn, ZnS˙CdS: Ag, X-rays of the type ZnS˙CdS : Ag, various rare-earth phosphors based on oxysulfides and strontium-barium sulfate and with ultraviolet rays, mainly calcium halophosphate with antimony and manganese [1].

 The disadvantages of these phosphors are the high cost of rare-earth activators and silver, the toxicity of antimony and the high temperature synthesis of oxysulfide silicate, halophosphate phosphors.

 Self-activated phosphors based on tungsten compounds are also known, namely magnesium and zinc tungstates, in which radiation in the spectral range of 0.5-0.7 μm is excited by gamma-cathode, X-ray and ultraviolet rays [2]. The advantage of these phosphors is a very wide range of applications, due to the variety of types of excitation of luminescence.

The disadvantages of these phosphors are low brightness and high (1000-1200 ^about C) temperature from the synthesis.

 The aim of the invention is to increase the brightness of the self-activated phosphor based on tungsten compounds and reduce energy consumption in the process of obtaining it.

The goal is achieved in that the self-activated phosphor with radiation in the spectral range of 0.5-0.7 μm based on a tungsten compound is barium tungsten fluoride BaWF ₈ , which is obtained from a mixture of oxides or hydroxides or carbonates of barium and tungsten taken in equimolar terms by hydrothermal synthesis in concentrated hydrofluoric acid at 150-260 ^{° C} for 2-4 hours.

The structure of this material is a framework of WF ₆ octahedra, in the voids between which are barium atoms, as well as in tungsten fluorides of other metals.

 In FIG. 1 shows the excitation and luminescence spectra; in FIG. 2 is a diagram of a synthesis device.

Radiation in the spectral range of 0.5-0.7 μm has barium tungsten fluoride BaWF ₈ . The luminescence color is golden yellow, the glow is excited by cathode, x-rays and ultraviolet light. Luminescence is very bright, with the same excitation, it is many times brighter than the glow of magnesium tungsten and 2-3 times brighter than the glow of mass photoluminophore in fluorescent lamps of LDC - calcium halophosphate activated by antimony and manganese. The color of the radiation is the same for all types of excitation; its spectrum is shown by curves 2 and 3 in FIG. 1: curve 2 - photoluminescence, curve 3 - cathodoluminescence. The contour of the X-ray luminescence band coincides with the contour of the photoluminescence band. Curve 1 (Fig. 1) shows the photoluminescence excitation spectrum. It can be seen here that the excitation band is very wide and homogeneous, extending from 150 to 400 nm, i.e. Includes all strong lines of UV radiation from mercury vapor.

 The maximum of the luminescence band is at λ = 530 nm.

The half-width of the band is about 150 nm,
Duration of cathodoluminescence attenuation 2x10 ^-4 s,
The maximum intensity of X-ray luminescence occurs in the temperature range from (-100) to (-40) ^о С, and at room temperature it is 93% of the maximum and decreases strongly only after 60 ^о С.

The resistance of the phosphor to the action of exciting radiation is high: when an electron beam is excited with a density of 1 KA / cm ² with an energy of 100 KeV, neither burn-out nor dehydration of the phosphor is observed. Under the influence of electrons, X-ray and ultraviolet radiation, color centers are not formed (at room temperature).

 The essence of the method is as follows.

Barium tungsten fluoride is synthesized in the form of a fine crystalline powder with a crystal size of a few tenths of a millimeter. The crystals are colorless, well-faceted, elongated prismatic, formed by a combination of tetragonal prism [110] and pinacoid [001], have a hatching on the prism faces along the elongation. The hardness of crystals is 3-2.5 according to the Mohs scale, the refractive indices are Mg = 1.485, Np = 1.472, Np-Ng = 0.013, specific gravity is 4.3 g / cm ³ , cleavage is absent. An important property is the non-hygroscopic nature of the material and its insolubility in water. An analysis of the composition of the synthesis product on a microprobe showed that it contains equimolar amounts of barium and tungsten fluorides.

Volframftorid barium prepared by hydrothermal synthesis from a mixture of oxides or hydroxides or carbonates of barium and tungsten, taken in the molar ratio 1: 1., In concentrated hydrofluoric acid at 150-260 ^{° C} for 2-4 hours The charge was placed on the bottom cup of polytetrafluorethylene , fill the cup with hydrofluoric acid at 1/2 of its height, close the lid with fluoroplastic and place in the autoclave of the VNIISIM design (Fig. 2), seal the autoclave, place it in the oven, heat it, and maintain it at a given temperature. After that, the autoclave is cooled to room temperature, opened under draft, acid is poured into a special vessel and the synthesis product is washed repeatedly with water, which is then removed from the glass and dried.

 The synthesis device (Fig. 2) contains a fluoroplastic glass 1 and a cover 2, a steel autoclave 3 and its cover 4, the bottom 5, the cover 6, the rack 7 and the nut 8 of the clamping device.

PRI me R 1. Synthesize crystals of barium tungsten fluoride from a mixture of BaO and WO ₃ (in the form of chemical reagents brand ChDA), taken in a molar ratio of 1: 1. A sample of 3 g of BaO and 4.8 g of WO _{3 is} placed on the bottom of the fluoroplastic cup 1, filled with hydrofluoric acid at half the height, closed with a lid 2 and placed in a autoclave 3, the lid 4 will be placed on the lid 2, the autoclave will be placed on the bottom 5 clamping device and on the lid 4 put a steel lid 6, in the grooves of which the racks 7 are inserted. Alternately tightening the nuts 8, press the lid 6 on the lid 6 and the lid 2 on it to the beaker 1. The ftoroplast, deforming, seals the autoclave. Thereafter, the clamping device with the autoclave was placed in a muffle furnace and the temperature was raised to 220 ^{° C,} at which the material is maintained in the autoclave for 3 hours. Then cut off the muffle. After cooling the muffle to room temperature, the device is removed from it, the autoclave is removed from it under draft, opened, the acid is drained into the corresponding vessel. The resulting material was repeatedly washed with distilled water, placed on a filter paper and dried in an oven at ⁹⁰ ° C for 2 hours. The resulting material is a powder of crystals of a few tenths of mm. The crystals are transparent, colorless, well-faceted, short-prismatic and tetragonal.

PRI me R 2. Equimolar mixtures of BaO and WO ₃ weighing 10 g each are processed for 2 hours according to example 1 at 100, 150, 180, 200, 260 and 280 ^about C, dried, weighed and emitted reaction products under the binocular , visually assessing the quality of the synthesis product (table. 1). From the table. 1 shows that the lower limit of the synthesis temperature is 150 C and ^the upper - 260 ^o C. Further, the temperature increase is impractical because it accelerates the fusion process.

PRI me R 3. The stoichiometric mixture of example 2 is subjected to processing at 200 ^about C from 1 to 48 hours and evaluate the yield of the product. The synthesis takes place successfully in 2-4 hours, an increase in the synthesis time over 4 hours is impractical, i.e. does not give an additional positive effect. Thus, 2 hours is the lower limit of the synthesis time interval, and 4 hours is the upper limit.

PRI me R 4. The material obtained in example 1, and the shots from the tube of a fluorescent fluorescent lamp - phosphor 2Ca ₃ (PO ₄ ) ₂ : Ca (F, Cl) ₂ : Mn alternately excite ultraviolet light of a mercury lamp with lengths waves up to 400 nm. In calcium halophosphate, a faint pale pink glow is excited; in a barium tungsten fluoride, a second brighter glow of golden yellow is excited.

 PRI me R 5. The material in example 1 is excited according to example 4 and using two monochromators, a photodetector and a recorder record the spectra of luminescence and its excitation. They are represented by curves 2 and 1 in FIG. 1, where it is seen that the excitation band is uniform and wide, it covers the entire ultraviolet range, its maximum is at 250 nm, i.e. almost coincides with the strongest mercury vapor emission line (λ = 254 nm); the photoluminescence band is also homogeneous, covers (by 1/3 of the height) the interval of 0.65 microns and has a maximum at 550 nm.

 PRI me R 6. The material according to example 1 is excited by radiation of an x-ray tube (U = 90 KV, I = 14 MA) and using the PMT-19A and the MDR-4 monochromator register the luminescence spectrum. It is shown by curve 2 in FIG. 1, since the contours of the X-ray and photoluminescence bands coincide.

 In the table. Figure 2 shows the luminescence intensity at different T.

 PRI me R 7. Excite the luminescence according to example 6 of the material according to example 1 and ethanol - industrial scintillator T1 and compare the luminescence intensity. It turned out that at room temperature the X-ray luminescence intensity of barium tungsten fluoride is 70% of the reference.

EXAMPLE 8. Using a pulsed electron accelerator (energy 200 keV, pulse duration 1x10 ^-9 s, power density 0.5-1 KA / cm ² ), the cathodoluminescence of barium tungsten fluoride is excited and its spectrum is recorded on an O analyzer AR-4 with a diffraction grating of 100 pieces / mm. The spectrum is represented by curve 3 in FIG. 1. This curve is heterogeneous, it has a main maximum at 530 nm and weak lateral maxima of about 480 and 600 mm.

PRI me R 9. Exciting luminescence according to example 8, register using the oscilloscope the decay time of luminescence. It is 2x10 ^-4 s.

 The above examples show that the described phosphor is an effective self-activated cathode, X-ray, and photoluminophore with golden yellow emission.

 The luminescence bands have a maximum of about 530 nm, a half-width of about 150 nm.

 The photoexcitation band is wide, uniform, and has a gently sloping maximum of about 250 nm, i.e. ultraviolet radiation of mercury vapor is fully used to excite luminescence, and sensitizers are not required.

 The second photoluminescence brightness is higher than the brightness of calcium halophosphate activated by antimony and manganese.

The intensity of X-ray luminescence is 70% of the reference (reference industrial scintillator NaF: T1) and does not depend much on temperature in the range from (-60 ^о С to (+60) ^о С.

 The phosphor is resistant to exciting radiation and to the action of atmospheric moisture, is synthesized easily, quickly and without the use of high temperatures.

 The described phosphor in comparison with the known cathode, X-ray and photoluminophores with radiation in the spectral region of 0.5-0.7 μm has a higher brightness, lower cost, does not contain toxic substances.

 Thus, barium tungsten fluoride is an effective cathode, X-ray, and photoluminophore, promising for use in electron-optical devices, X-ray amplification and projection screens, in fluorescent fluorescent lamps, and the method for its production does not require the use of high temperatures, is not accompanied by the formation of dust and vapors of heavy metals and is suitable for industrial development.

Claims (3)

 SELF-ACTIVATED LUMINOPHOR WITH RADIATION IN THE FIELD OF 0.5 - 0.7 MKM AND THE METHOD OF ITS PRODUCTION. 1. Self-activated phosphor with radiation in the region of 0.5-0.7 μm based on a tungsten-containing compound of an alkaline earth metal, characterized in that, in order to increase the brightness of the phosphor and reduce the energy consumption of the process for its production, it is barium tungsten fluoride of the formula BaWF ₆ . 2. A method of producing a self-activated phosphor with radiation in the region of 0.5-0.7 μm, comprising the interaction of an alkaline earth metal compound, a tungsten and fluorine-containing compound when heated, characterized in that, in order to increase the brightness of the phosphor and reduce the energy consumption of the process, compounds of an alkaline earth metal and a tungsten-containing compound use an oxide, or hydroxide, or barium carbonate and tungsten oxide, taken in an equimolar ratio, and the process is carried out in a concentrated melt melt acid in an autoclave at 160-260 ^o C for 2-4 hours

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