JP2014240465A - Production method of nitride phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nitride phosphor represented by CaAlSiN:Eu by calcining a precursor alloy powder, by which a nitride phosphor is inexpensively obtained by calcining the powder in a nitrogen-containing atmosphere at normal pressure without using Eu metal that is expensive and troublesome in handling as a raw material.SOLUTION: A nitride phosphor represented by CaAlSiN:Eu is produced by subjecting Ca metal, Si metal, Al oxide and Eu oxide as raw materials and Ca metal as a reducing agent, in which the amount of the Al oxide is 1.05 to 1.3 times as much as an amount necessary for an alloy composition of the precursor, to a reduction process at a temperature of 1000°C or higher; cleaning the obtained reaction product to obtain a precursor alloy powder; and calcining the precursor alloy powder in a nitrogen-containing atmosphere at normal pressure to produce.

Description

  The present invention relates to a method for manufacturing a nitride phosphor, and more particularly to a method for inexpensively manufacturing a nitride phosphor that emits red fluorescence in the emission wavelength region of a near-ultraviolet light emitting diode or a blue light emitting diode.

In recent years, the development of white LEDs has progressed, and it is expected as illumination replacing incandescent lamps and fluorescent lamps. In a conventional white LED, a phosphor in which Ce is added to a YAG-based oxide known from the composition formula of (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ is dispersed in a blue LED sealing resin. The thing (refer patent document 1) is known. These white LEDs are used in the front light of a mobile phone, a simple lighting device, and the like, but have poor color reproducibility and color rendering, and their improvement has been demanded.

In response to this demand, currently there are blue-excited white LEDs that combine blue LEDs, green phosphors, and red phosphors, and ultraviolet-excited white LEDs that combine ultraviolet light-emitting LEDs, blue phosphors, green phosphors, and red phosphors. Has been developed. Among these phosphors used for white LEDs, nitride phosphors represented by CaAlSiN ₃ : Eu (usually called CASN) (see Patent Document 2) are widely used as red phosphors.

For the production of the nitride phosphor, as raw materials, calcium nitride (Ca ₃ N ₂ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), europium nitride (EuN) or europium oxide (Eu ₂ O ₃ ) Is used. However, divalent metal nitride calcium nitride (Ca ₃ N ₂ ) is unstable in an atmosphere containing moisture, and easily reacts with moisture to produce hydroxide. For this reason, handling in the atmosphere is not preferable, and handling with raw material blending and the like has to be performed in a state where it is shielded from the atmosphere, such as in a glove box filled with an inert gas.

  In addition, when manufacturing the above-mentioned nitride phosphor, since the reactivity of the raw material powder used is low, the solid phase reaction between the nitride powders of the raw material is not promoted at low temperatures, and the target phosphor is produced. Therefore, it was necessary to fire at a high temperature of 1800 ° C. or higher. However, when firing at such a high temperature, there arises a disadvantage that a decomposition reaction of the nitride raw material accompanied by desorption of nitrogen occurs. In order to suppress the decomposition of the nitride raw material, it is necessary to perform firing in a high-pressure nitrogen gas atmosphere of 0.5 MPa or more. Therefore, high firing energy is required and a very expensive high-temperature high-pressure firing furnace is necessary. Thus, the manufacturing cost of the phosphor is increased.

Therefore, as a method for solving these problems, a method for producing the nitride phosphor using a metal as a starting material has been proposed (see Patent Document 3). According to this method, alloy powder obtained by using Ca, Al, Si, and Eu as raw materials, casting a molten metal of CaAlSiEu alloy obtained by melting these metals, and then pulverizing the alloy lump. Can be fired in a nitrogen-containing atmosphere to produce a nitride phosphor typified by CaAlSiN ₃ : Eu. It is said that the nitride phosphor can be manufactured even when the pressure of the nitrogen gas atmosphere during firing is set to atmospheric pressure (nitrogen gas circulation).

Japanese Patent No. 2900928 Japanese Patent No. 3837588 JP 2006-307182 A

The method for producing a nitride phosphor typified by CaAlSiN ₃ : Eu described in Patent Document 3 does not require the precursor CaAlSiEu alloy powder to be fired in a high-pressure nitrogen-containing atmosphere. Since Eu metal is used, handling of Eu metal that is easily oxidized in the atmosphere is troublesome, and Eu metal is expensive and causes an increase in cost.

  Moreover, since the boiling point (1494 ° C.) of the Ca metal that is the raw material is close to the melting point (1410 ° C.) of the Si metal, an Al—Si alloy (melting point 1010 ° C.) is cast first, and then Ca metal and Eu metal are added. Therefore, it was necessary to cast the desired precursor CaAlSiEu alloy. Moreover, since it is necessary to pulverize the precursor alloy lump obtained, there is a problem that the process is troublesome and complicated.

The present invention has been made in view of such a conventional situation, and a precursor phosphor of CaAlSiEu is fired in a nitrogen-containing atmosphere to produce a nitride phosphor typified by CaAlSiN ₃ : Eu. In this case, a method of producing a nitride phosphor at low cost by firing a precursor CaAlSiEu alloy powder in a nitrogen-containing atmosphere at a normal pressure without using an expensive and troublesome Eu metal as a raw material. The purpose is to provide.

In order to achieve the above object, a method for producing a nitride phosphor provided by the present invention includes a nitridation represented by a general formula Ca _1-x AlSiN ₃ : Eu _x (where 0.005 ≦ x ≦ 0.02). things phosphor, _{Ca 1-x} AlSiEu x alloy as the precursor (where, 0.005 ≦ x ≦ 0.02) a process for producing by calcining,
Using Ca metal, Si metal, Al oxide and Eu oxide as raw materials and Ca metal as a reducing agent, the amount of Al oxide is 1.05-1.3 times the amount required for the alloy composition of the precursor. and to prepare a raw material powder mixture, the raw material powder mixture reduced at 1000 ° C. or higher, to obtain a powder of Ca _1-x AlSiEu _x alloy which is a precursor by washing the reaction product obtained Thereafter, the precursor alloy powder is fired in a nitrogen-containing atmosphere.

  In the method for producing a nitride phosphor according to the present invention, the amount of Ca metal as the reducing agent is 1.0 to 1.1 which is an amount necessary for the reduction of Al oxide and Eu oxide in the raw material powder mixture. It is preferable that it is double.

According to the present invention, Ca metal, Si metal, Al oxide and Eu oxide, which are inexpensive and easy to handle, are used as raw materials, and a precursor CaAlSiEu alloy powder is produced by a relatively simple and easy process. be able to. Therefore, by firing the precursor alloy powder in an atmosphere containing nitrogen at normal pressure, a nitride phosphor typified by CaAlSiN ₃ : Eu can be produced easily and at low cost.

It is a graph which shows the fluorescence spectrum in excitation wavelength 455nm of each nitride fluorescent substance obtained in Example 1 and 2 and the prior art examples 1 and 2. FIG.

Manufacturing method of the nitride phosphor of the present invention have the general formula _{Ca 1-x AlSiN 3: Eu} x ( where 0.005 ≦ x ≦ 0.02, hereinafter the same) of the nitride phosphor represented by, the precursor a method of manufacturing by sintering of _{Ca 1-x} AlSiEu x alloy is body, Ca metal as a raw material, Si metal, the Al oxide and Eu oxide, further adding a Ca metal as the reducing agent, the raw material A raw material adjustment step for adjusting the powder mixture, a reduction step for reducing the obtained raw material powder mixture at a temperature of 1000 ° C. or higher, a reaction product obtained in the reduction step is washed, and the precursor Ca _A cleaning process for obtaining a powder of _1-x AlSiEu _x alloy, and a precursor alloy powder obtained in the cleaning process is fired in a nitrogen-containing atmosphere at a temperature of 1000 ° C. or more to obtain nitride phosphor Ca _1-x AlSiN _3: comprising a firing step to obtain a u _x.

In the raw material adjustment step, first, each raw material powder of Ca metal, Si metal, Al oxide (Al ₂ O ₃ ), and Eu oxide (Eu ₂ O ₃ ) is weighed so as to have a desired precursor alloy composition. In addition, a Ca metal powder is added and mixed as a reducing agent for reducing the oxide.

In this raw material adjustment step, CaO produced by reduction of the oxide during the reduction process in the next step reacts with the raw material Al ₂ O ₃ to produce 12CaO · 7Al ₂ O _3, so this 12CaO · 7Al ₂ in anticipation of formation of O _3, it is necessary to larger amount added than the amount required to Al oxides the amount of _(Al 2 _{O 3)} a composition of _{Ca 1-x} AlSiEu x alloy of the precursor. Specifically, the addition amount of Al oxides, in the range of 1.05 to 1.3 times the amount necessary to obtain a _{Ca 1-x} AlSiEu x alloy composition of the precursor. If the added amount of the Al oxide is less than 1.05 times, Al forming the alloy is insufficient, so that a CaSi alloy or the like is generated in addition to the Ca _1-x AlSiEux alloy, and _if the added amount exceeds 1.3 times, CaAl ₂ Since an alloy having a composition with a large amount of Al such as Si _1.5 is generated and mixed, a precursor alloy having the above-mentioned single composition cannot be obtained in any case.

Moreover, the addition amount of Ca metal added as a reducing agent needs at least the theoretical amount for reducing the oxide in a raw material powder mixture. In addition, since Ca metal tends to volatilize, you may add more than a theoretical amount in consideration of the possibility of volatilization. However, if the amount of Ca metal as a reducing agent is too large, the alloy having the composition Ca often against Ca _1-x AlSiEu _x alloy composition of the precursor to produce the desired, addition of Ca metal The amount is preferably 1.0 to 1.1 times the theoretical amount for reducing the oxide in the raw powder mixture.

However, when calculating the amount of Ca metal necessary for the reduction of the oxide, the increased amount of Al ₂ O ₃ added in anticipation of the formation of 12CaO · 7Al ₂ O _{3 as} described above is due to the reduction of the oxide. Since it is consumed by the reaction with CaO that has been made, it is not subject to calculation of the required amount of Ca metal.

  In the next reduction step, the raw material powder mixture prepared in the raw material preparation step is heated at a temperature of 1000 ° C. or higher in an atmosphere that is substantially free of oxygen, for example, an inert gas atmosphere such as argon. I do.

The heat reduction treatment is performed under an inert gas atmosphere such as argon or helium, and the treatment temperature is 1000 ° C. or higher. Treatment temperature is not sufficiently reduced oxides is less than 1000 ° C., since leaves a oxide in the reaction product, it does not contribute to the formation of the Ca _1-x AlSiEu _x alloy which is a precursor. However, if the treatment temperature is too high, the Ca metal volatilizes and becomes deficient, and the oxide may remain without being reduced. Therefore, the treatment temperature is preferably 1200 ° C. or lower.

  Thereafter, in the washing step, the reaction product obtained in the reduction step is cooled to room temperature and then poured into ion-exchanged water. By repeating agitation and decantation several times, CaO produced by reduction of the oxide or Impurities such as residual reducing agent are dissolved and removed to recover the precursor alloy powder.

By this washing with water, 12CaO · 7Al ₂ O ₃ produced by the reaction of CaO and Al ₂ O _{3 in the} reduction step also floats in water, and can be completely separated by repeating washing with water. In addition, some reaction products exist in a state where particles on the order of several tens of μm are loosely aggregated. In that case, the reaction product is lightly pulverized with a mortar or the like and then placed in ion-exchanged water. By introducing it, good cleaning efficiency can be obtained.

The reaction product obtained in the reduction step naturally collapses into a powder state during washing with ion-exchanged water. As a result, the powder obtained after completion of cleaning is a powder of _{Ca 1-x} AlSiEu x alloy which is a precursor, the particle diameter is substantially within the range of 10 to 20 [mu] m. Thus, the powder of the Ca _1-x AlSiEu _x alloy can be further without having to provide pulverizing step is supplied as a precursor alloy powder to sintering step is as the next step.

  In the washing step, it is preferable to carry out pickling with a weak acid such as acetic acid after repeating washing with water as described above. In that case, after the pickled precursor alloy powder is washed again with water, the alloy powder is separated and recovered and dried. Moreover, it is preferable that the pH at the time of pickling exists in the range of 4.0-6.0. If the pH during pickling is less than 4.0, the precursor alloy may be dissolved by the acid, and if the pH exceeds 6.0, the effect of pickling may not be obtained. .

Finally, in the firing step, the precursor alloy powder obtained in the above cleaning step by firing in a nitrogen-containing atmosphere, the general formula Ca _{1-x AlSiN 3:} nitride phosphor represented by Eu _x is obtained It is done. The nitrogen-containing atmosphere at the time of firing does not need to be particularly pressurized and may be normal pressure (atmospheric pressure).

  The nitrogen-containing atmosphere may be a nitrogen gas atmosphere, an oxygen atmosphere containing nitrogen, or an air atmosphere containing nitrogen. Moreover, although there is no restriction | limiting in particular in baking temperature and baking time, As conditions for obtaining the desired nitride fluorescent substance efficiently, baking temperature is the range of 1500 degreeC-1800 degreeC, and baking time is 5 hours-10 hours. A range is preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

[Example 1]
The raw material powder was Ca metal: 4.12 g, Si metal: 2.92 g, Al ₂ O ₃ : 6.36 g, Eu ₂ O ₃ : so that the alloy composition of the precursor was Ca _0.99 AlSiEu _0.01. 0.18 g and Ca metal: 6.94 g as a reducing agent were weighed and mixed in a mortar. At this time, the amount of Al ₂ O ₃ was 1.2 times the amount necessary to obtain the alloy composition of the precursor. Further, the amount of Ca metal added as a reducing agent was 1.1 times the amount necessary for reducing the oxide in the raw material powder.

Note that the added amount of Al ₂ O ₃ added in anticipation of the formation of 12CaO · 7Al ₂ O ₃ is consumed by the reaction with CaO formed by the reduction of the oxide, so this increased amount is reduced by the reduction of the oxide. Is not included in the calculation of the amount of Ca metal required for the process. That is, in the present embodiment 1, _Al 2 _{O 3} of 5.30g is reduced by Ca metal, is _Al 2 _{O 3} remaining 1.06g consumed by reaction with CaO.

  The mixture of the raw material powders was put into a heating container, the inside of the heating container was evacuated, and then a heat reduction treatment was performed at 1150 ° C. for 5 hours while flowing an argon gas to obtain a reaction product. This reaction product was put into ion-exchanged water and washed with water by repeating stirring and decantation six times. Next, the mixture was put into an acetic acid aqueous solution, and the mixture was stirred for 30 minutes while adjusting the pH with 2 mol / l acetic acid so as to maintain the pH of 5, followed by pickling, and then again in deionized water for deoxidation. Purified.

Thereafter, the precipitated alloy powder was collected and dried to obtain an alloy powder that became a precursor of the nitride phosphor. When the composition of the obtained precursor alloy powder was confirmed by an X-ray diffraction method, it was found to be Ca _0.99 AlSiEu _0.01 .

The precursor alloy powder was fired at 1600 ° C. for 5 hours while flowing normal pressure nitrogen gas to produce a nitride phosphor. When the composition of this nitride phosphor was confirmed by X-ray diffraction, it was found to be Ca _0.99 AlSiN ₃ : Eu _0.01 . Further, as a result of measuring the fluorescence spectrum of this nitride phosphor at an excitation wavelength of 455 nm, it was confirmed that the nitride phosphor was a red phosphor emitting fluorescence with a fluorescence peak wavelength of 650 nm as shown in FIG.

[Example 2]
As in Example 1 above, each raw material powder was weighed and mixed so that the precursor alloy composition was Ca _0.99 AlSiEu _0.01 , but the amount of Al ₂ O ₃ was set to the desired alloy composition. Therefore, it was set to 1.05 times the amount necessary for this. The amount of Ca metal added as a reducing agent was 1.05 times the amount necessary for reducing the oxide in the raw material powder mixture.

  The raw material powder mixture was put into a heating container, the inside of the heating container was evacuated, and then a reduction treatment was performed at 1000 ° C. for 5 hours while flowing an argon gas to obtain a reaction product. This reaction product was washed in the same manner as in Example 1, and the resulting precursor alloy powder was fired in the same manner as in Example 1 to produce a nitride phosphor.

The composition of this nitride phosphor was confirmed in the same manner as in Example 1 and found to be Ca _0.99 AlSiN ₃ : Eu _0.01 . Further, the fluorescence spectrum of the nitride phosphor at an excitation wavelength of 455 nm was measured, and the result is shown in FIG.

[Comparative Example 1]
Similar to Example 1 above, Ca metal, Si metal, Al ₂ O ₃ , Eu ₂ O ₃ and Ca metal as a reducing agent so that the alloy composition of the precursor is Ca _0.99 AlSiEu _0.01. Were weighed and mixed. However, the amount of Al ₂ O ₃ was not required to produce 12CaO · 7Al ₂ O ₃ , and was an amount necessary for obtaining the alloy composition of the precursor. The amount of Ca metal as the reducing agent was 1.1 times the amount necessary for the reduction of the oxide.

The mixture of the raw material powders was put into a heating container, the inside of the heating container was evacuated, and then a reduction treatment was performed at 1000 ° C. for 5 hours while flowing argon gas to obtain a reaction product. The reaction product was washed in the same manner as in Example 1 and the composition of the obtained precursor alloy powder was confirmed by X-ray diffraction. As a result, the peak of Ca _0.99 AlSiEu _0.01 (CaAlSi structure) was observed. In addition, a peak of CaSi alloy was observed, and a single composition precursor alloy was not obtained.

[Comparative Example 2]
Similar to Example 1 above, Ca metal, Si metal, Al ₂ O ₃ , Eu ₂ O ₃ and Ca metal as a reducing agent so that the alloy composition of the precursor is Ca _0.99 AlSiEu _0.01. Were weighed and mixed. At that time, the amount of Al ₂ O ₃ is 1.2 times the amount necessary to obtain the alloy composition of the precursor, and the amount of Ca metal as the reducing agent is the amount necessary for the reduction of the oxide. 1.1 times.

The mixture of the raw material powders was put into a heating container, the inside of the heating container was evacuated, and then a reduction treatment was performed at 950 ° C. for 5 hours while flowing argon gas to obtain a reaction product. The reaction product was washed in the same manner as in Example 1 and the composition of the obtained precursor alloy powder was confirmed by X-ray diffraction. As a result, the peaks of Si and Al ₂ O ₃ were observed together with the peaks of CaSi alloy. Observed, the desired precursor alloy of the above composition was not obtained.

[Conventional example 1]
Using nitrides of Ca, Al, Si, and Eu as raw materials, firing was performed in a high-pressure nitrogen atmosphere to produce a nitride phosphor. That is, Ca ₃ N ₂ , AlN, Si so that the metal nitride composition ratio of the obtained nitride phosphor is Ca: Al: Si: Eu = 0.99: 1.00: 1.00: 0.01 ₃ N ₄ and EuN are weighed and mixed in an Ar glove box, set in a hot isostatic press (HIP), and fired at 1800 ° C. for 2 hours in a 1.0 MPa high-pressure nitrogen atmosphere. It was.

The resulting nitride phosphor, was confirmed composition by the same X-ray diffraction method as in Example 1, Ca _0.99 AlSiN _3: was found to be Eu _0.01. Further, the fluorescence spectrum of the nitride phosphor at an excitation wavelength of 455 nm was measured, and the result is shown in FIG.

[Conventional example 2]
As in Conventional Example 1, each of nitrides of Ca, Al, Si, and Eu is used as a raw material, and the resulting nitride phosphor has a metal element composition ratio of Ca: Al: Si: Eu = 0.99: 1.00: It was weighed and mixed in an Ar glove box so as to be 1.00: 0.01, and calcination was carried out at 1600 ° C. for 5 hours while flowing normal pressure nitrogen gas. About the obtained nitride fluorescent substance, the fluorescence spectrum in excitation wavelength 455nm was measured, and the result was shown in FIG.

  As can be seen from the above Examples, Comparative Examples, and Conventional Examples, the emission characteristics of the nitride phosphors of Examples 1 and 2 obtained by the method of the present invention are as shown in FIG. This is substantially the same as the nitride phosphor of Conventional Example 1 manufactured by the conventional method of firing in a high-temperature, high-pressure nitrogen atmosphere as a raw material.

  Therefore, according to the method for producing a nitride phosphor of the present invention, it is possible to use Ca metal, Si metal, Al oxide, and Eu oxide that are inexpensive and easy to handle as a raw material, by a relatively simple and easy process. The precursor CaAlSiEu alloy powder can be produced, and further, by firing the precursor alloy powder in an atmospheric pressure nitrogen-containing atmosphere, without using an expensive Eu metal or high-temperature high-pressure firing furnace, A nitride phosphor that emits red light can be obtained.

Claims (3)

Formula _{Ca 1-x AlSiN 3: Eu} x ( where, 0.005 ≦ x ≦ 0.02) nitride phosphor represented by, _{Ca 1-x} AlSiEu x alloy as the precursor (0. 005 ≦ x ≦ 0.02) by firing,
Using Ca metal, Si metal, Al oxide and Eu oxide as raw materials and Ca metal as a reducing agent, the amount of Al oxide is 1.05-1.3 times the amount required for the alloy composition of the precursor. and to prepare a raw material powder mixture, the raw material powder mixture reduced at 1000 ° C. or higher, to obtain a powder of Ca _1-x AlSiEu _x alloy which is a precursor by washing the reaction product obtained Thereafter, the precursor alloy powder is fired in a nitrogen-containing atmosphere.   The amount of Ca metal as the reducing agent is 1.0 to 1.1 times the amount necessary for the reduction of Al oxide and Eu oxide in the raw material powder mixture. The manufacturing method of the nitride fluorescent substance of description.   3. The method for producing a nitride phosphor according to claim 1, wherein the temperature of the reduction treatment is 1000 ° C. or more and 1200 ° C. or less.

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