JPH0412314B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a phosphor. More specifically, the present invention relates to a method for producing a barium fluoride halide phosphor activated by divalent europium. Barium fluoride halide phosphors activated with divalent europium have high absorption efficiency for radiation such as X-rays, and can be excited by any type of radiation such as X-rays.
Because it exhibits near-ultraviolet light emission (instantaneous light emission) with an emission maximum around 390 nm, it is used in medical radiography such as X-ray photography for medical diagnosis and industrial radiography for the purpose of non-destructive testing of materials. It was known that it could be used as a phosphor for radiation-sensitizing screens. Furthermore, in recent years, divalent europium-activated barium fluoride halide phosphors absorb and accumulate part of the energy when irradiated with radiation such as X-rays, and then It has been found that the phosphor exhibits near-ultraviolet light emission when irradiated with electromagnetic waves in the region, that is, the phosphor exhibits stimulated luminescence. For these reasons, in recent years, divalent europium-activated barium fluoride halide phosphors have been used for radiation therapy that utilizes the photostimulability of phosphors, as disclosed in, for example, Japanese Patent Application Laid-open No. 12429/1983. It has attracted much attention as a phosphor for radiation image conversion panels used in image conversion methods, and much research has been conducted on it. For example, Japanese Patent Application Laid-Open No. 55-12143 discloses a radiation image conversion method in which a part of the barium constituting the matrix is replaced with another specific alkaline earth metal in a divalent europium-activated barium fluoride halide phosphor. Discloses a phosphor for panels. According to the publication, its composition formula is (Ba _1-xy MgxCay)FX:aEu ²⁺ (where X is
at least one of Br and Cl, x,
y and a are respectively 0<x+y≦0.6, xy≠0,
and 10 ^-6 ≦a≦5×10 ^-2 . ). By the way, when using a stimulable phosphor in a radiation image conversion panel for radiography such as X-ray photography for medical diagnosis, it is possible to reduce the exposure dose to the human body or to reduce the electrical processing required later. To facilitate this, it is desired that the brightness of the stimulated luminescence be as high as possible. Similarly, when a phosphor is used in a radiation intensifying screen that uses instantaneous light emission, the phosphor can produce the brightness of instantaneous light emission in order to minimize the exposure dose to the human body. It is desired that it be as high as possible. Therefore, for phosphors used in radiation image conversion panels or radiation intensifying screens, it is desired to develop a technology that improves the brightness of stimulated luminescence or instantaneous luminescence as much as possible for each application. . However, especially when the target of radiation irradiation is a human body, the degree of improvement in the brightness of instantaneous luminescence or stimulated luminescence does not necessarily have to be dramatic, and even if the degree is not large, the luminance of luminescence can be improved. Substantial improvements can be said to be of great significance when considering the impact they have on the human body. For the reasons mentioned above, the present invention provides divalent europium-activated fluorinated halides with improved stimulated luminescence brightness when excited with electromagnetic waves in the wavelength range of 450 to 800 nm after being irradiated with radiation such as X-rays. The object of the present invention is to provide a method for manufacturing barium phosphor. Another object of the present invention is to provide a method for producing a divalent europium-activated barium fluoride halide phosphor that has improved instantaneous luminance when excited by radiation such as X-rays. The above object can be achieved by the method for producing a phosphor of the present invention. That is, the phosphor provided by the present invention has the composition formula (): BaFX xA:yEu ²⁺ () (where X is at least one halogen selected from the group consisting of Cl, Br, and I; A is a fired product obtained by firing in a weakly reducing atmosphere at least one compound selected from the hexafluoro compound group consisting of monovalent or divalent metal salts of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluzirconium acid. and x is a numerical value in the range of 10 ^-6 ≦x≦0.1, and y is
It is a divalent europium-activated barium fluoride halide phosphor represented by the formula (0<y≦0.1). The divalent europium-activated barium fluoride halide phosphor represented by the above compositional formula () has a stoichiometric compositional formula (): BaFX:yEu () (where X is Cl, Br, and at least one kind of halogen selected from the group consisting of I; and y is a numerical value in the range of 0<y≦0.1). At least one compound selected from the hexafluoro compound group consisting of monovalent or divalent metal salts of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid is added to 1 gram atom of barium contained in the phosphor raw material mixture. x moles per unit (where x is 10 ^-6 ≦x≦0.1
This can be achieved by the production method of the present invention, which is characterized in that the mixture is mixed with a numeric value in the range of , and then the resulting mixture is fired in a weakly reducing atmosphere. The divalent europium-activated barium fluoride halide phosphor of the present invention having the composition formula () is
After irradiating the phosphor with radiation such as rays, ultraviolet rays, or electron beams, the phosphor is excited with electromagnetic waves in the wavelength range of 450 to 800 nm. It clearly shows stronger stimulated luminescence compared to when the same operation was performed. Furthermore, when the divalent europium activated barium fluoride halide phosphor of the present invention having the composition formula () is irradiated with radiation such as X-rays, ultraviolet rays, and electron beams, Compared to a similar operation using a barium chloride phosphor, it exhibits near-ultraviolet light emission (instantaneous light emission) with even higher brightness. Next, the present invention will be explained in detail. The divalent europium-activated barium fluoride halide phosphor of the present invention can be produced, for example, by the production method described below. First, as a phosphor raw material, 1 at least one barium halide selected from the group consisting of BaF ₂ (barium fluoride), 2 BaCl ₂ , BaBr ₂ , and BaI ₂ , 3 EuCl ₃ , EuBr ₃ , and EuI ₃ . at least one europium halide selected from the group consisting of; Prepare the compound. The metal constituting the hexafluoro compound in 4) above is selected from the 2nd to 6th periods of Group Ia of the periodic table due to its stability and the fact that it does not cause absorption or light emission in the luminescent region of the resulting phosphor. Alkali metals belonging to the 3rd to 6th period of group a, alkaline earth metals belonging to the 3rd to 6th period of group a, zinc, manganese, etc. are preferable. In addition, the above hexafluoro compound has the composition formula (): MaSiF ₆ () where a is 2 or 1, and when a = 2, M is a group consisting of Li, Na, K, Rb, and Cs. represents an alkali metal selected from a
When =1, M represents a divalent metal selected from the group consisting of Mg, Ca, Sr, Ba, Zn, and Mn. Furthermore, a of Ma in the above composition ()
It is particularly preferred that 2 and M is an alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs. Alternatively, the above hexafluoro compound, compositional formula (): M ₂ QF ₆ () (where Q is Zr or Ti, M is Li,
It is also preferable that the compound is an alkali metal selected from the group consisting of Na, K, Rb, and Cs. When manufacturing a phosphor, first, barium fluoride (1) above, barium halide (2) barium halide, and europium halide (3) above are stoichiometrically prepared using the composition formula (): BaFX:yEu () ( However, X is at least one kind of halogen selected from the group consisting of Cl, Br, and I; and y is a numerical value in the range of 0<y≦0.1). Weigh and mix. This mixing operation is performed in a suspension state. Thereafter, water is removed from the suspension of the phosphor raw material mixture to obtain a solid dry mixture. This water removal operation is preferably carried out at room temperature or at a not very high temperature (for example, 200°C or less) by drying under reduced pressure, vacuum drying, or both. Next, the obtained dry mixture is finely pulverized using a mortar or the like, and then the hexafluoro compound of 4) above is added to the pulverized product in x mol per gram atom of barium contained in the dry mixture (however, x is
10 ^-6 ≦x≦0.1) and thoroughly mixed to obtain a hexafluoro compound-containing phosphor material mixture. In the phosphor of the present invention, from the viewpoint of the luminance of stimulated luminescence or instantaneous luminescence when irradiated with radiation such as X-rays, the above X and y are each 10 ^-4 ≦
It is particularly preferred that x≦10 ^-2 and 10 ^-5 ≦y≦10 ^-2 . Next, the phosphor raw material mixture obtained as described above is filled into a heat-resistant container such as a quartz boat, an alumina crucible, or a quartz crucible, and fired in an electric furnace. A suitable firing temperature is 600 to 1000°C. Although the firing time varies depending on the filling amount of the phosphor raw material mixture and the firing temperature, 0.5 to 12 hours is generally appropriate. As the firing atmosphere, a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing carbon monoxide is used. That is, the weakly reducing atmosphere reduces trivalent europium to divalent europium during the firing process. After firing the mixture of phosphor raw materials under the above firing conditions, the fired product is taken out of the electric furnace, left to cool, and then pulverized.Then, the fired product powder is again filled into a heat-resistant container and heated. It may be placed in a furnace for re-firing. The firing temperature during re-firing is 500
~800°C and firing time of 0.5 to 12 hours is appropriate. In addition to the weakly reducing atmosphere mentioned above, the firing atmosphere for refiring is a nitrogen gas atmosphere,
A neutral atmosphere such as an argon gas atmosphere can be used. Finally, the fired product that has undergone the firing process is finely ground to obtain a powdered phosphor of the present invention. In addition, regarding the obtained powdered phosphor, if necessary,
Additionally, various common operations in the manufacture of phosphors such as washing, drying, sieving, etc. may be performed. The divalent europium-activated barium fluoride halide phosphor produced by the production method described above has a composition formula (): BaFX xA:yEu ²⁺ () (where X, x, and y The definition is the same as above; and A is at least one compound selected from the group of hexafluoro compounds consisting of monovalent or divalent metal salts of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid. It is a fired product obtained by firing in a weakly reducing atmosphere.) The value of x in the phosphor of the present invention represented by the above compositional formula (), that is, a hexafluoro compound group consisting of monovalent or divalent metal salts of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid. The relationship between the luminance of the phosphor of the present invention, which is obtained by firing at least one compound selected from the following in a weakly reducing atmosphere (hereinafter simply referred to as the fired product), is, for example, the first
The relationship is as shown in the graph in the figure. Figure 1 shows the composition formula of an example of the phosphor of the present invention.
BaFBr・xA: 0.001Eu ²⁺ (A is Na ₂ SiF ₆
The tube voltage is applied to the phosphor represented by
After irradiating with 80KVp X-rays, the brightness of stimulated luminescence when excited with He-Ne laser light (wavelength 632.8nm) and the content of the fired sodium hexafluorosilicate product in the phosphor (x value: (corresponding to the amount of sodium hexafluorosilicate added to the phosphor raw material). As is clear from FIG. 1, the luminance of stimulated luminescence of the divalent europium-activated barium fluoride halide phosphor increases by adding sodium hexafluorosilicate within a certain range. The luminance reaches its maximum when its content (x value) is approximately 3.3×10 ^-3 (the molar amount of sodium hexafluorochate added per gram atom of barium in the phosphor); If it exceeds 0.1, the luminance will conversely decrease. This trend is
The same effect appears when A in the compositional formula () is changed to a fired product of the other hexaful compound mentioned above. Further, FIG. 1 shows the relationship between the x value and the luminescence brightness in stimulated luminescence of an example of the phosphor of the present invention. The same applies to the relationship between the x value and the luminance. As described above, the phosphor of the present invention has a luminance of stimulated luminescence when irradiated with radiation such as X-rays and then electromagnetic waves in the wavelength range of 450 to 800 nm.
This is a clear increase compared to the conventional divalent europium activated barium fluoride halide phosphor. Furthermore, the phosphor of the present invention also increases the brightness of instantaneous light emission when irradiated with radiation such as X-rays, compared to the conventional divalent europium-activated barium fluoride halide phosphor. Therefore, the phosphor of the present invention is very useful particularly as a phosphor for radiation image conversion panels or as a phosphor for radiation sensitization. Next, Examples and Comparative Examples of the present invention will be described. However, these examples do not limit the invention. [Example 1] 175.34 g of barium fluoride (BaF ₂ ), 333.18 g of barium bromide (BaBr ₂ 2H ₂ O), and 0.783 g of europium bromide (EuBr ₃ ) were added to 500 g of distilled water (H ₂ O).
cc and mixed to form a suspension. This suspension was dried under reduced pressure at 60°C for 3 hours, and then further vacuum dried at 150°C for 3 hours. After the dried product was finely ground using a mortar, 1.24 g of sodium hexafluorosilicate (Na ₂ SiF ₆ ) was added to the ground product and mixed to obtain a uniform mixture. Next, the obtained phosphor raw material mixture was filled into an alumina crucible, which was then placed in a high-temperature electric furnace and fired. Firing was performed at a temperature of 900° C. for 1.5 hours in a carbon dioxide atmosphere containing carbon monoxide. After the firing was completed, the fired product was taken out of the furnace and cooled. The obtained fired product is pulverized to form a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・3.3×10 ^-3 A: 0.001Eu ²⁺ ; where A represents the fired Na ₂ SiF ₆ obtained). [Example 2] Using barium fluoride, barium bromide, europium bromide, and distilled water in the amounts described in Example 1, a suspension was prepared, dried, and pulverized in the same manner. 0.124 g of sodium hexafluorosilicate (Na ₂ SiF ₆ ) was added to the mixture and mixed to form a homogeneous mixture. By using the above phosphor raw material mixture and performing the same operation as in Example 1, a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・3.3×10 ^-4 A: 0.001Eu ²⁺ ; However, A
was a fired product of Na ₂ SiF ₆ ). [Example 3] A suspension was prepared, dried and pulverized in the same manner using barium fluoride, barium bromide, europium bromide and distilled water in the amounts described in Example 1. 3.72 g of sodium hexafluorosilicate (Na ₂ SiF ₆ ) was added to the mixture and mixed to form a homogeneous mixture. By using the above phosphor raw material mixture and performing the same operation as in Example 1, a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・9.9×10 ^-3 A: 0.001Eu ²⁺ ; However, A
was a fired product of Na ₂ SiF ₆ ). [Example 4] A suspension was prepared, dried and pulverized in the same manner using barium fluoride, barium bromide, europium bromide and distilled water in the amounts described in Example 1. 37.61 g of sodium hexafluorosilicate (Na ₂ SiF ₆ ) was added to the mixture and mixed to form a homogeneous mixture. By using the above phosphor raw material mixture and performing the same operation as in Example 1, a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・0.1A: 0.001Eu ²⁺ ; , A is
A fired product of Na ₂ SiF ₆ was obtained. [Comparative Example 1] A suspension was prepared, dried and pulverized in the same manner using barium fluoride, barium bromide, europium bromide and distilled water in the amounts described in Example 1, and a pulverized product was obtained. I got it. By using the above phosphor raw material mixture (pulverized material) and performing the same operation as in Example 1,
A powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr: 0.001Eu ²⁺ ) was obtained. Next, each of the phosphors obtained in Examples 1 to 4 and Comparative Example 1 was irradiated with X-rays with a tube voltage of 80 KVp, and then excited with He-Ne laser light (wavelength 632.8 nm) to make the fluorescent substances The stimulated luminance of the body was measured. The results are shown in Table 1.

[Table] [Example 5] 175.34 g of barium fluoride (BaF ₂ ), 333.18 g of barium bromide (BaBr ₂ 2H ₂ O), and 0.783 g of europium bromide (EuBr ₃ ) were added to distilled water (H ₂ O). 500
cc and mixed to form a suspension. This suspension was dried under reduced pressure at 60°C for 3 hours, and then further vacuum dried at 150°C for 3 hours. After finely pulverizing the dried product using a mortar, calcium hexafluorosilicate (CaSiF ₆ 2H ₂ O) is added to the pulverized product.
1.44g was added and mixed to form a homogeneous mixture. Next, the obtained phosphor raw material mixture was filled into an alumina crucible, which was then placed in a high-temperature electric furnace and fired. Firing was performed at a temperature of 900° C. for 1.5 hours in a carbon dioxide atmosphere containing carbon monoxide. After the firing was completed, the fired product was taken out of the furnace and cooled. After the obtained fired product was pulverized, the fired product powder was again filled into the alumina crucible and fired (secondary firing) at a temperature of 600° C. for 1 hour in a nitrogen atmosphere. After the secondary firing is completed, the fired product is cooled and finely pulverized to produce a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・3.3×10 ^-3 A: 0.001Eu ^{2 +} ; However, A
was a calcined product of CaSiF ₆ ). [Example 6] Using barium fluoride, barium bromide, europium bromide, and distilled water in the amounts described in Example 5, a suspension was prepared, dried, and pulverized in the same manner. 0.144 g of calcium hexafluorosilicate (CaSiF ₆ ) was added to the mixture and mixed to form a homogeneous mixture. By using the above phosphor raw material mixture and performing the same operation as in Example 5, a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・3.3×10 ^-4 A: 0.001Eu ²⁺ ; However, A
was a calcined product of CaSiF ₆ ). [Example 7] Using barium fluoride, barium bromide, europium bromide, and distilled water in the amounts described in Example 5, a suspension was prepared, dried, and pulverized in the same manner. 4.32 g of calcium hexafluorosilicate (CaSiF ₆ ) was added to the mixture and mixed to form a homogeneous mixture. By using the above phosphor raw material mixture and performing the same operation as in Example 5, a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・9.9×10 ^-3 A: 0.001Eu × ²⁺ ; However,
A is a fired product of CaSiF ₆ ) was obtained. Next, the phosphors obtained in Examples 5, 6, and 7 were
After irradiating with X-rays at a tube voltage of 80 KVp, the tubes were excited with He--Ne laser light (wavelength: 632.8 nm) and the brightness of stimulated luminescence of these phosphors was measured. The results are shown in Table 2. Also, in Table 2,
The results for the phosphor of Comparative Example 1 are also shown.

[Table] [Example 8] 175.34 g of barium fluoride (BaF ₂ ), 333.18 g of barium bromide (BaBr ₂ 2H ₂ O), and 0.783 g of europium bromide (EuBr ₃ ) were added to distilled water (H ₂ O). 500
cc and mixed to form a suspension. This suspension was dried under reduced pressure at 60℃ for 3 hours, and then further dried at 15℃ for 3 hours.
Vacuum drying was performed for hours. After finely pulverizing the dried product using a mortar, 1.37 g of sodium hexafluorotitanate (Na ₂ TiF ₆ ) was added to the pulverized product and mixed to form a uniform mixture. By using the above phosphor raw material mixture and performing the same operation as in Example 1, a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・3.3×10 ^-3 A: 0.001Eu ²⁺ ; However, A
was a fired product of Na ₂ TiF ₆ ). Next, the tube voltage was applied to the phosphor obtained in Example 8.
After irradiating with 80 KVp X-rays, the phosphor was excited with He--Ne laser light (wavelength: 632.8 nm) and the brightness of stimulated luminescence of the phosphor was measured. The results are shown in Table 3. Also, in Table 3,
The results for the phosphor of Comparative Example 1 are also listed.

[Table] [Example 9] 175.34 g of barium fluoride (BaF ₂ ), 333.18 g of barium bromide (BaBr ₂ 2H ₂ O), and 0.783 g of europium bromide (EuBr ₃ ) were added to distilled water (H ₂ O). 500
cc and mixed to form a suspension. This suspension was dried under reduced pressure at 60°C for 3 hours, and then further vacuum dried at 150°C for 3 hours. After the dried product is finely ground using a mortar, sodium hexafluorozirconate (Na ₂ ZrF ₆ ) is added to the ground product.
1.66g was added and mixed to form a homogeneous mixture. By using the above phosphor raw material mixture and performing the same operation as in Example 1, a powdered divalent europium-activated barium fluoride bromide phosphor (BaFBr・3.3×10 ^-3 A: 0.001Eu ²⁺ ; However, A
was a fired product of Na ₂ ZrF ₆ ). Next, the tube voltage was applied to the phosphor obtained in Example 9.
After irradiating with X-rays of 80 KVp, it was excited with He--Ne laser light (wavelength: 632.8 nm) and the brightness of stimulated luminescence of the phosphor was measured. The results are shown in Table 4. Also, in Table 4,
The results for the phosphor of Comparative Example 1 are also listed.

【table】 [Brief explanation of drawings]

FIG. 1 shows the composition formula BaFBr xA: 0.001Eu ²⁺ (where A is
The content (x value) of the sodium hexafluorosilicate fired product in the phosphor represented by (which is a fired product obtained by firing Na ₂ SiF ₆ in a weakly reducing atmosphere);
FIG. 2 is a diagram showing a typical relationship between the luminance of stimulated luminescence when excited with He-Ne laser light (wavelength 632.8 nm) after irradiation with X-rays with a tube voltage of 80 KVp.

Claims (1)

[Claims] 1 Stoichiometric compositional formula (): BaFX:yEu () (wherein, X is at least one halogen selected from the group consisting of Cl, Br, and , 0<y≦0.1) is added to the phosphor raw material mixture mixed in a relative ratio corresponding to At least one hexafluoro compound selected from the hexafluoro compound group consisting of salts of valent metals is added to x moles per gram atom of barium contained in the phosphor raw material mixture (where x is
10 ^-6 ≦x≦0.1) and then firing the resulting mixture in a weakly reducing atmosphere. Law. 2. Production of a divalent europium activated barium fluoride halide phosphor according to claim 1, wherein the weakly reducing firing atmosphere is a nitrogen gas atmosphere containing hydrogen gas or a carbon dioxide atmosphere containing carbon monoxide. Law. 3. The method for producing a divalent europium-activated barium fluoride halide phosphor according to claim 1, wherein x is a numerical value in the range of 10 ^-4 ≦x≦10 ^-2 . 4 Claim 1, wherein the firing temperature is 600 to 1000°C
A method for producing a divalent europium-activated barium fluoride halide phosphor as described in . 5. The divalent europium-activated halogen fluoride according to claim 1, which comprises a step of once firing in a weakly reducing atmosphere, pulverizing the fired product, and then re-calcining in a weakly reducing atmosphere or a neutral atmosphere. Method for manufacturing barium chloride phosphor. 6 The metals constituting the monovalent or divalent metal salt are Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba,
2. The method for producing a divalent europium-activated barium fluoride halide phosphor according to claim 1, wherein the metal is at least one metal selected from the group consisting of Zn and Mn. 7 The hexafluoro compound has the composition formula () M _a SiF ₆ () (where a is 2 or 1, and when a = 2, M is from the group consisting of Li, Na, K, Rb, and Cs. represents the selected alkali metal, and a
When = 1, M is Mg, Ca, Sr, Ba, Zn,
2. The method for producing a divalent europium-activated barium fluoride halide phosphor according to claim 1, which is at least one metal salt selected from the group consisting of Mn and Mn. 8 In the compositional formula (), a of M _a is 2, and M is
8. The method for producing a divalent europium-activated barium fluoride halide phosphor according to claim 7, wherein the alkali metal is selected from the group consisting of Li, Na, K, Rb, and Cs. 9 The hexafluoro compound has the composition formula () M ₂ QF ₆ () (where Q is Zr or Ti, M is Li,
The divalent europium-activated barium fluoride halide phosphor according to claim 1, which is an alkali metal selected from the group consisting of Na, K, Rb, and Cs. manufacturing method.