TWI450947B - Method for producing β-sialon - Google Patents

Description

Method for producing β-type lanthanum aluminum oxynitride

The present invention relates to a method for producing a β-type lanthanum aluminum oxynitride which solid-solves lanthanum (Eu).

Patent Document 1 describes a method for producing a β-type lanthanum aluminum oxynitride in which Eu is dissolved, and an acid-treated solution of hydrofluoric acid and nitric acid is used to chemically dissolve β of Eu. The technical content of the luminescence intensity improvement of the bismuth aluminum oxynitride. However, Patent Document 1 also discloses a technique in which a phosphor dissolves when the concentration of the mixed acid solution is high, and when the temperature is 60 ° C or higher, the phosphor dissolves.

Patent Document 2 discloses that in order to increase the luminescence intensity of β-type lanthanum aluminum oxynitride in which Eu is dissolved, the pulverized fired product is further dried at 1300 ° C to 1600 ° C in an inert gas other than nitrogen. After heating, a technique of acid treatment using a mixed acid solution of 50% hydrofluoric acid and 70% nitric acid is used.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-255885

[Patent Document 2] International Publication No. 2008/062781

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a β-type lanthanum aluminum oxynitride which is solid-solubilized with Eu which is reproducible in achieving higher luminous efficiency.

The present invention is based on the use of a mixed acid solution of hydrofluoric acid and nitric acid in the acid treatment step, if the concentration of the mixed acid solution is lowered, the luminous intensity of the obtained phosphor will become low, but at a higher temperature, the luminous intensity will be The new insights that have become higher. This knowledge is described in Patent Document 1 "If the concentration of the mixed acid solution is high, the β-type lanthanum aluminum oxynitride in which Eu is dissolved is dissolved, so it is less desirable" and the "mixed acid treatment temperature is lower". Reveal the opposite result.

The present invention relates to a method for producing a β-type lanthanum aluminum oxynitride, which is a β-type lanthanum aluminum oxynitride represented by the general formula: Si _6-z Al _z O _z N _8-z (0<z≦4.2). A method for producing a solid solution of Eu-type β-alumina aluminum oxynitride, comprising: a first heating step of firing a raw material mixed powder containing Si, Al, and Eu in a nitrogen atmosphere; and the obtained fired product is a second heating step of performing heat treatment in an inert gas atmosphere or in a vacuum; and a step of performing acid treatment in a mixed acid solution of hydrofluoric acid and nitric acid at a temperature range exceeding 60 ° C and 100 ° C or less after the second heating step .

By the method of the present invention, ?-type lanthanum aluminum oxynitride which is solid-solved with Eu having high luminous efficiency can be produced with good reproducibility.

[Formation for implementing the invention]

The present invention relates to a method for producing a β-type lanthanum aluminum oxynitride which dissolves Eu, which comprises: a first heating step of firing a raw material mixed powder containing Si, Al, and Eu in a nitrogen atmosphere; a second heating step of heat-treating the material in an inert gas atmosphere or in a vacuum; and, after the second heating step, in a mixed acid solution of hydrofluoric acid and nitric acid at a temperature exceeding 60 ° C and below 100 ° C The step of acid treatment is carried out.

The raw material mixed powder containing Si, Al, and Eu refers to a cerium compound containing cerium oxide and/or aluminum oxide, cerium nitride, aluminum nitride, a metal selected from cerium, an oxide, a carbonate, a nitride, or an oxynitride. The powder to be mixed.

The raw material containing Si and Al is blended so as to satisfy the general formula: Si _6-z Al _z O _z N _8-z (0 < z ≦ 4.2).

The Eu content is preferably in the range of 0.1% by mass or more and 3% by mass or less. If the Eu content is within the above range, the luminance of the light can be sufficiently obtained.

When a raw material containing Si, Al, or Eu is mixed, a method of performing dry mixing is carried out, and a method of removing the solvent after performing wet mixing in an inert solvent that does not substantially react with each component of the raw material is Any method can also be applied in the present invention. As the mixing device, a V-type mixer, a rocking mixer, a ball mill, a vibration mill, or the like can be used.

The raw material mixed powder is dried as needed, and then filled in a container such as a crucible in which at least the surface on which the raw material is in contact is formed into boron nitride, and heated in a nitrogen atmosphere.

The mixed raw material mixed powder is heated in a nitrogen atmosphere at a temperature of from 1820 ° C to 2200 ° C, preferably from 1850 ° C to 2050 ° C (hereinafter referred to as a first heating step). If the heating temperature is low, Eu can not enter the β-type yttrium aluminum oxynitride crystal. If the heating temperature is increased above the required temperature, a higher nitrogen pressure must be applied to suppress the Eu-solution β-type lanthanum aluminum oxynitride. Decomposition of matter. The pressure condition in the firing is preferably 0.5 MPa or more and 10 MPa or less. The heating time is generally from 10 hours to 20 hours.

In the case of the raw material mixed powder, it is also possible to use a metal powder containing Si instead of using tantalum nitride. At this time, the metal powder containing Si must be subjected to nitriding treatment before the first heating step. The nitridation reaction of the Si-containing metal powder is performed at a temperature of 1400 ° C to 1600 ° C. Therefore, the Si-containing metal powder is heated under the above-mentioned temperature range to convert Si into a nitrogen atmosphere before the first heating step. Si ₃ N ₄ .

Next, after the first heating step, the obtained fired product is additionally heated in a vacuum or a gas atmosphere other than nitrogen (hereinafter referred to as a second heating step). This second heating step serves to make the low crystalline portion remaining in the fired material more unstable. The low crystal phase which becomes unstable due to the second heating step treatment is removed by the mixed acid solution treatment described later.

In order to make the low crystalline portion unstable, it is preferred to heat-treat the fired product in a gas atmosphere in which nitrogen and oxygen belonging to the element constituting the low crystalline portion are not contained as much as possible. When the second heating step is performed in a gas atmosphere other than nitrogen, after the exhausting step, the heating furnace is filled with an inert gas (hereinafter referred to as an introduction step). The inert gas system is selected from the group consisting of helium, neon, argon, xenon, krypton, xenon, and hydrogen, preferably argon or hydrogen.

In the second heating step, the fired product is heated in a temperature range of 1200 ° C to 1550 ° C or less in a vacuum or in a temperature range of 1300 ° C to 1550 ° C in an inert gas atmosphere. If the heating temperature is within this temperature range, the decomposition of Eu-solution β-type lanthanum aluminum oxynitride can be suppressed.

After the second heating step, the acid treatment step is advanced. In the acid treatment step, the fired product obtained by the second heating step is pulverized, and the pulverized fired product is dispersed in a mixed acid solution of hydrofluoric acid and nitric acid, and stirred at a temperature exceeding 60 ° C. . The acid treatment step is a step of removing the unstabilized low crystalline portion by immersion in an acidic liquid.

The temperature of the acid treatment exceeds a temperature range of 60 ° C or lower. If it is excessively low in temperature, the luminescence intensity of the Eu-soluble β-type lanthanum aluminum oxynitride is lowered.

The mixed solution of hydrofluoric acid and nitric acid may be a mixture of hydrofluoric acid of about 50% concentration and nitric acid of about 70% concentration (hereinafter referred to as mixed stock solution) or diluted with the mixed stock solution (the following mixed liquid solution) Diluted is called mixed acid solution). The concentration of the solution diluted with the mixed stock solution is preferably 25% or more and less than 100%, more preferably 25% or more and 50%. Instead of diluting a high concentration of a mixed solution of hydrofluoric acid and nitric acid, a diluted low concentration of hydrofluoric acid and nitric acid may be mixed.

When the mixing ratio of hydrofluoric acid and nitric acid is mixed with hydrofluoric acid having a concentration of about 50% and nitric acid having a concentration of about 70%, a ratio of from 1 to 9:9 to 1 is preferred, and particularly preferably from 3 to 3. 7:7~3.

The mixed solution is preferably a mixture of concentrated hydrofluoric acid and concentrated nitric acid. Concentrated hydrofluoric acid means that the concentration is 40% or more and 60% or less, and concentrated nitric acid means a concentration of 55% or more and 75% or less.

[Example 1]

Hereinafter, an embodiment of the present invention will be described in detail with reference to Table 1. Table 1 shows the processing conditions and light-emitting characteristics of Examples 1 to 7 and Comparative Examples 1 and 2 described later.

Blending α-type tantalum nitride powder (SN-E grade 10 made by Ube Industries, Ltd., oxygen content 1.1% by mass, β phase content 4.5% by mass) 95.4% by mass, aluminum nitride powder (F grade, Tokuyama company, oxygen content) 0.8% by mass of 3.0% by mass, alumina powder (TM-DAR grade manufactured by Daming Chemical Co., Ltd.), 0.74% by mass, and cerium oxide powder (RU grade manufactured by Shin-Etsu Chemical Co., Ltd.) were 0.71% by mass, and 600 g of a raw material mixture was obtained.

The obtained raw material mixture was dry-mixed for 60 minutes by a rocking mixer (RM-10 manufactured by Aichi Electric Co., Ltd.), and all of them were passed through a stainless steel sieve having a mesh opening of 150 μm to obtain a raw material powder.

The obtained raw material powder was filled with 170 g of a cylindrical boron nitride container (N-1 grade, manufactured by Denki Kagaku Co., Ltd.) having a diameter of 10 cm, a height of 9 cm, and a thickness of 0.5 cm, in a carbon heater. The electric furnace was fired at 1950 ° C for 15 hours in a pressurized nitrogen atmosphere of 0.9 MPa as a first heating step. The obtained calcined product was cleaved and passed through a sieve having a mesh size of 45 μm to obtain a powder.

The obtained powder was filled with 20 g of a cylindrical boron nitride container (N-1 grade, manufactured by Denki Kagaku Co., Ltd.) having a diameter of 6 cm, a height of 3.5 cm, and a thickness of 0.5 cm. The furnace was subjected to heat treatment at 1400 ° C for 8 hours in a vacuum as a second heating step.

25 ml of 50% hydrofluoric acid (HF) and 25 ml of 70% nitric acid (HNO ₃ ) were mixed to form a mixed stock solution. 150 ml of distilled water was added to the mixed stock solution, and the concentration of the mixed stock solution was diluted to 25% to adjust 200 ml of the HF + HNO ₃ aqueous solution. 5 g of the powder after the second heating step was charged, and the HF + HNO ₃ aqueous solution was maintained at 70 ° C for one hour of acid treatment.

The powder after the acid treatment was sufficiently washed with distilled water to filter the acid, dried, and passed through a sieve having a mesh opening of 45 μm to obtain a phosphor powder of Example 1.

Next, the full-beam luminescence spectrum was measured using the integrating sphere for the phosphor powder of Example 1 (Reference: Lighting Society, Vol. 83, No. 2, Heisei 11 (2000), p87-93, Determination of the quantum efficiency of NBS standard phosphors, Okubo and Akira). The excitation light system uses a split xenon light source.

The evaluation of the produced β-type lanthanum aluminum oxynitride was carried out as shown in Table 1, and was carried out by the light-absorption characteristics, the internal quantum efficiency, and the external quantum efficiency.

At the time of this evaluation, a standard reflection plate (Labsphere, Spectralon (registered trademark)) having a reflectance of 99% was placed in the sample portion to measure the spectrum of the excitation light, and when the excitation wavelength was 455 nm, the wavelength range was from 450 to 465 nm. The spectrum is used to calculate the number of excitation photons (Qex). Then, the phosphor is placed in the sample portion, and the obtained spectral data is used to calculate the number of photons (Qref) and the number of photons (Qem) of the excited reflected light. The three kinds of photons are used to obtain the light absorption rate (=(Qex-Qref)×100), the internal quantum efficiency (=Qem/(Qex-Qref)×100), and the external quantum efficiency (=Qem/Qex×100). The number of photons of the excitation reflection light is in the same wavelength range as the number of photons of the excitation light, and the number of fluorescence photons is calculated in the range of 465 to 800 nm when the excitation light is 455 nm.

The luminescent properties in Example 1 were 72.5% for light absorption, 69.9% for internal quantum efficiency, and 50.7% for external quantum efficiency.

[Embodiment 2]

The method for producing β-type lanthanum aluminum oxynitride of Example 2 is the same as in Example 1 except that the temperature of the acid treatment is 80° C., the light absorptivity is 71.8%, the internal quantum efficiency is 71.4%, and the external method. Quantum 51.2%.

[Example 3]

The method for producing β-type lanthanum aluminum oxynitride of Example 3 was the same as in Example 1 except that the temperature of the acid treatment was 90° C., and the light absorptance was 71.2%, the internal quantum efficiency was 72.0%, and the external method was used. Quantum 51.3%.

[Example 4]

In the fourth embodiment, an acid treatment step is carried out to mix 15 ml of hydrofluoric acid (HF) and 50 ml of 70% strength nitric acid (HNO ₃ ) to form a mixed stock solution, and 150 ml of distilled water is added to the mixed stock solution to mix. 200 ml of an aqueous solution of HF+HNO _{3 was} adjusted so that the stock solution was diluted and the concentration was 25%. In the same manner as in Example 1, except that 5 g of the powder after the second heating step was placed, the HF + HNO ₃ aqueous solution was maintained at 80 ° C for 1 hour. In the case of Example 4, the light absorption rate was 71.6%, the internal quantum efficiency was 70.9%, and the external quantum efficiency was 50.8%.

[Example 5]

Example 5 is a production method in which the same conditions as in Example 4 are carried out except that 35 ml of hydrofluoric acid (50%) and 15 ml of 70% hydrochloric acid are mixed to form a mixed stock solution. In the case of Example 5, the light absorption rate was 71.7%, the internal quantum efficiency was 71.3%, and the external quantum efficiency was 51.1%.

[Embodiment 6]

In Example 6, 50 ml of 50% hydrofluoric acid and 50 ml of 70% nitric acid were mixed to form a mixed stock solution. 100 ml of distilled water was added to the mixed stock solution, and the mixed stock solution was diluted to adjust 200 ml of an aqueous solution of HF + HNO _{3 having a} concentration of 50%. The same was carried out except that the HF+HNO ₃ aqueous solution was kept at 80 ° C while the acid treatment was carried out for 1 hour, except that 5 g of the powder after the second heating step was placed. In the case of Example 6, the light absorption rate was 74.7%, the internal quantum efficiency was 70.0%, and the external quantum efficiency was 52.3%.

[Embodiment 7]

Example 7 was carried out in the same manner as in Example 6 except that distilled water was not used as the acid in the acid treatment of Example 6, except that 100% of the stock solution concentration of 100 ml was used. In Example 7, the light absorption rate was 72.9%, the internal quantum efficiency was 72.6%, and the external quantum efficiency was 52.9%.

(Comparative Example 1)

Comparative Example 1 was set to the same conditions as in Example 1 except that the acid treatment temperature was changed to 60 °C. The light absorption rate was 72.0%, the internal quantum efficiency was 69.2%, and the external quantum efficiency was 49.8%.

(Comparative Example 2)

Comparative Example 2 was carried out under the same conditions as in Example 6 except that the acid treatment temperature was 35 °C. In the case of Comparative Example 2, the light absorptance was 73.6%, the internal quantum efficiency was 68.8%, and the external quantum efficiency was 50.6%.

From Examples 1, 2, and 3 and Comparative Example 1, it is understood that the light absorption rate, the internal quantum efficiency, and the external quantum efficiency are improved by increasing the temperature of the acid treatment. The treatment temperature may be more than 60 ° C and 100 ° C or less, and preferably 70 ° C or more and 90 ° C or less.

It is understood from Examples 1 to 5 and Comparative Example 2 that even if the concentration of the mixed acid solution in the acid treatment step is relatively thin, in particular, the mixed stock solution is diluted to have a concentration of 25% or more and 50%, as compared with the conventional example. In Comparative Example 2, any of the light absorptivity, the internal quantum efficiency, and the external quantum efficiency was improved. As is apparent from Comparative Examples 1 and 2, when the concentration of the mixed acid solution was diluted, the light-emitting characteristics were lowered.

[Embodiment 8]

Although not shown in the table, a light-emitting device in which an anthrone sealing resin containing β-type lanthanum aluminum oxynitride used in the examples and the comparative examples was laminated on the light-emitting surface of the LED was produced. When the β-type lanthanum aluminum oxynitrides of Examples 1 to 7 were used, after the light was emitted, even after being left at a high temperature of 80 ° C × humidity of 40% for 2 hours, no decrease in luminescent properties was observed. On the other hand, in the light-emitting device using the β-type lanthanum aluminum oxynitride of Comparative Examples 1 and 2, it was found that the light-emitting characteristics were lowered.

[Industrial availability]

When the β-type lanthanum aluminum oxynitride of the present invention is used as a phosphor, it is excited by a wide wavelength range of ultraviolet to blue light, and exhibits high-luminance green light, so that it can be suitably used as blue or The ultraviolet light is a phosphor of a white LED of a light source, and can be suitably used for a lighting fixture, an image display device, or the like.

Claims (2)

A method for producing β-type lanthanum aluminum oxynitride, which is dissolved on β-type lanthanum aluminum oxynitride represented by the general formula: Si _6-z Al _z O _z N _8-z (0<z≦4.2) A method for producing a β-type lanthanum aluminum oxynitride of Eu, comprising: a first heating step of firing a raw material mixed powder containing Si, Al, and Eu in a nitrogen atmosphere; and the obtained fired material in an inert gas atmosphere a second heating step of heat treatment in a medium or vacuum; and a step of acid treatment in a mixed acid solution of hydrofluoric acid and nitric acid at a temperature range exceeding 60 ° C and 100 ° C or less after the second heating step, the mixed acid The solution was obtained by mixing 50% hydrofluoric acid and 70% nitric acid in a volume ratio (50% hydrofluoric acid/70% nitric acid) at a ratio of 1 to 9/9 to 1. The method for producing a β-type lanthanum aluminum oxynitride according to the first aspect of the invention, wherein the mixed acid solution is prepared by mixing concentrated hydrofluoric acid and concentrated nitric acid, and the dilution ratio is 25% or more.