KR20000001988A - Preparation method of zinc galliumate powder by ultrasonic spray pyrolysis - Google Patents

Abstract

PURPOSE: Zinc galliumate useful as low voltage phosphor is manufactured by spraying mixed liquid of zinc nitrate and gallium nitrate by using an ultrasonic and heat-decomposing at 92000-1,200°C. CONSTITUTION: Zinc nitrate and gallium nitrate are melted in water in a ratio of Zn/Ga of 0.4-0.5 and added with 0.1-1 weight% of manganese nitrate, the mixed liquid is sprayed by using an ultrasonic oscillator(4). The sprayed mist is conveyed with carrier gas to a furnace and heat-decomposed at 92000-1,200°C. For example, 1.894g zinc nitrate and 5.155g gallium nitrate are melted in water in 100mL flask to give 100mL of 0.1M solution, which is poured into a receptacle with an ultrasonic oscillator. Oxygen is blown into the receptacle at 30sccm(standard cubic centimeters per minute, cm¬3/min). The temperature of furnace is raised to 1,100°C. A size of power particle shows a narrow distribution of 0.1-2 micro meter, a mean particle size is about 0.5 micro meter.

Description

Method for producing zinc gallium powder by ultrasonic spray pyrolysis

The present invention relates to a method for producing zinc gallium phosphate powder by ultrasonic spray pyrolysis, and more specifically, to a mixture of zinc nitrate and gallium nitrate, including spraying and pyrolyzing an aqueous solution of zinc nitrate and gallium nitrate. The present invention relates to a method of preparing a zinc gallium phosphate powder by easily controlling particle size and suppressing generation of by-products.

Cathode ray tubes have been widely used in most displays since they were developed over 100 years ago and have very good performance. However, this cathode ray tube has the disadvantage that its volume or weight rapidly increases as the size of the screen increases, and as a technique for overcoming this disadvantage, a flat panel display device has been studied. Field emission display (FED) device.

This FED device consists of an anode coated with a field emitter, a gate and a low voltage phosphor. Recently, much research has been conducted on this, and a small prototype is currently manufactured. However, in the case of FED devices, it is essential to develop phosphors that operate at low voltage and have excellent fluorescence properties, as the present color televisions using cathode ray tubes are made possible by the development of red phosphors having a narrow band spectrum. Currently, metal sulfide phosphors are widely used in vacuum fluorescent display devices, which decompose when colliding with electrons to release polluting gases (sulfides), which reduces efficiency and shortens the lifetime of the cathode filament. To excite the electron, a voltage of 8 kV or higher is required. As a phosphor that solves the above problems and shows good fluorescence properties at low voltage, those reported so far include zinc oxide (A. Vecht, DW Smith, SS Chandha, CS Gibbons, J. Koh, and D. Morton). , J. Vac. Sci. Technol. B 12, 781 (1994)), zinc silicate (K. Su, TD Tilley, and MJ Sailor, J. Am. Chem. Soc., 118, 3459 (1996) ) And zinc gallate (see S. Itoh, H. Toki, Y. Sato, K. Morimoto, and T. Kishino, J. Electrochem. Soc., 138, 1509 (1991)). There is a complex oxide.

Among these, spinel-based zinc galliumate, which operates in the blue region, has recently been known to be a low voltage phosphor for FED. As a method for producing zinc gallate has been reported so far, zinc oxide (ZnO) and gallium oxide (Ga ₂ O ₃ ) is mixed in a constant stoichiometric ratio to prepare a powder through a solid phase reaction (S. Itoh, H. Toki, Y. Sato, K. Morimoto, and T. Kishino, J. Electrochem. Soc., 138, 1509 (1991)], are mainly used and radio wave magnetron sputtering using a target made of this material An example of a thin film has been reported by radiofrequency magnetron sputtering (see IJ Hsieh, KT Chu, CF Yu, and MS Feng, J. Appl. Phys., 76, 3735 (1994)). However, this solid phase reaction has the disadvantage that it is difficult to mix the reactants uniformly, resulting in the production of a single oxide as a byproduct.

On the other hand, ultrasonic spray pyrolysis (see TT Kodas, Angew. Chem. Int. Ed. Adv. Mater., 28, 794 (1989)), which is used for the production of complex oxide powders such as superconductors and magnetic bodies, is a complex oxide. The stoichiometric ratio of can be controlled relatively easily, and the reactants can be mixed uniformly to suppress the formation of a single oxide, and the size of the produced particles can be controlled by adjusting the concentration of the solution and the micron (μm). The following very small ultrafine powders can also be produced. The metal salts used should be of high solubility in water or other solvents, and should be those which produce gases that can be easily decomposed and removed without causing contamination from the product during the pyrolysis process. Accordingly, many examples have been reported of metal nitrates or metal oxalates which are decomposed into NO ₂ or CO ₂ at relatively low temperatures to produce metal oxides.

However, no examples of producing zinc gallium sulfate using the ultrasonic spray pyrolysis as described above have been reported. Therefore, the present inventors have continued their research, using zinc nitrate and gallium nitrate as sources of zinc and gallium. Ultrasonic spray pyrolysis has been found to solve the problem of the production of zinc galliumate by the solid phase reaction has been completed the present invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing zinc galliumate powder purely by using an ultrasonic spray pyrolysis method, which facilitates introduction of admixtures and particle size control of products and suppresses the generation of by-products.

1 is a schematic view of the ultrasonic spray pyrolysis apparatus used in the present invention,

2 is an X-ray diffraction pattern (top) of zinc gallium phosphate powder prepared from Example 2 (using 0.05M mixed aqueous solution of zinc nitrate and gallium nitrate) according to the present invention, and a standard X-ray diffraction pattern of zinc galliumate (bottom) )ego,

3 is an X-ray diffraction pattern of zinc gallium phosphate powder prepared from Example 4 (using a 0.3 M mixed aqueous solution of zinc nitrate and gallium nitrate) according to the present invention,

4A and 4B are scanning electron micrographs of zinc galliumate powder prepared from Examples 2 and 4, respectively, according to the present invention;

5 is an X-ray photoelectron spectrum of a zinc gallium phosphate powder mixed with Mn prepared from Example 6 according to the present invention,

6a and 6b are photoluminescence spectra of zinc galliumate powder prepared from Examples 4 and 5 (reduction treatment addition), respectively, according to the present invention;

7A and 7B are photoluminescence spectra of zinc galliumate powder prepared from Examples 4 and 6 (Mn incorporation) according to the present invention, respectively.

<Brief Description of Drawings>

1: carrier gas supply line 2: mixed aqueous solution of zinc nitrate and gallium nitrate

3: water for cooling 4: ultrasonic vibrator

5: humidifier 6: spray droplet outlet

7: Tygon Tube 8: Spray Droplet Inlet

9: aluminum plug 10: quartz glass reaction tube

11: heating furnace 12: aluminum coupler

13: Zinc Gallate Powder Collector 14: Reaction Gas Outlet

15: bubbler 16: outlet

In order to achieve the above object, in the present invention, zinc nitrate and gallium nitrate are dissolved in water so that Zn / Ga is in the range of 0.4 to 0.5, and the resulting aqueous solution is sprayed using an ultrasonic vibrator, and then the sprayed droplets are transported. Provided is a method for producing zinc galliumate powder, which comprises transporting the gas to a furnace and pyrolyzing at 900 to 1200 ° C.

Hereinafter, the present invention will be described in more detail.

The starting material used in the production of the zinc galliumate powder according to the present invention is a metal nitrate, in which zinc nitrate and gallium nitrate are used as the sources of zinc and gallium, respectively. The zinc nitrate and gallium nitrate are weighed so that Zn / Ga is in the range of 0.4 to 0.5 and dissolved in deionized water to a desired concentration to obtain a transparent mixed aqueous solution. At this time, by adjusting the concentration of the mixed aqueous solution to 5 to 20% by weight can be adjusted to the particle size of the zinc gallium phosphate powder in the range of 0.1 to 3 ㎛, the lower the concentration of the mixed aqueous solution within the above range the smaller the particle size of the powder .

In addition, according to the present invention, the nitrate of the metal to be mixed in the preparation of the mixed aqueous solution is added in the range of 0.1 to 1% by weight of zinc nitrate to finally contain a metal dopant in the zinc gallium phosphate phosphor produced It is possible to narrow the band butterflies of the photoluminescence spectrum of the product. The metal admixture includes manganese nitrate, chromium nitrate and europium nitrate, and manganese nitrate is particularly preferable.

According to the present invention, zinc gallium phosphate powder may be prepared using a conventional ultrasonic spray pyrolysis apparatus composed of an atomizer, a furnace, and a collector from the zinc / gallium mixed aqueous solution. Specifically, zinc gallium sulfate is sprayed by spraying an aqueous zinc / gallium mixed solution through an atomizer of an ultrasonic spray pyrolysis apparatus and transferring the sprayed droplets to a furnace together with a carrier gas such as hydrogen or air to pyrolyze at a temperature in the range of 900 to 1200 ° C. The powder can be collected.

According to the present invention, the zinc gallium phosphate powder is photoluminescent by reducing the powder at 700 to 1200 ° C. for 5 to 24 hours while flowing a nitrogen gas containing about 5% by weight of hydrogen gas to the produced zinc gallate powder. The intensity of the spectrum can be increased by 2 to 50 times.

According to the ultrasonic spray pyrolysis according to the present invention, the reactants used in the production of zinc galliumate can be uniformly mixed, and the gallium acid, which is a low voltage phosphor for FED, is suppressed by facilitating introduction of admixture and control of particle size. Zinc can be prepared in powder form with high purity.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the invention only.

Figure 1 shows a schematic diagram of the ultrasonic spray pyrolysis apparatus used in the embodiment of the present invention, it was prepared by the following method:

As a nebulizer, a domestic humidifier 5 with a power consumption of 42 W having an ultrasonic vibrator 4 having a frequency of 1.65 MHz was used. As a container for the aqueous solution of metal nitrate (2), a Pyrex test tube having a diameter of 40 mm and a height of 15 cm including an O-ring was used, and the upper side of the vibrator was placed so that the vibrator 4 was placed in the center of the open lower end. This test tube was bonded to the bottom of the spray tank using epoxy adhesive. A hole of 8 mm in diameter and 7 cm in length was attached to the cap of the test tube so that it could be used as a supply gas (1) for the carrier gas. Spray droplet outlet 6). The vertical furnace 11 is composed of two alumina heat sources, each of which controls the temperature of the two zones (zone) and is designed to raise the temperature up to 1200 ℃. The inner diameter of the furnace 11 was made 50 mm and length 50 cm. The quartz glass reaction tube 10 was inserted into the center of the furnace 11, and the quartz tube 10 was 45 mm in inner diameter and 70 cm in length, and both ends thereof were exposed to each other 10 cm above and below the furnace. On the quartz tube 10, an aluminum stopper 9 is attached using an O-ring to block the outside, and a hole 10 mm in diameter (spray droplet inlet 8) to allow sprayed droplets to flow therein. Came out. Insert a 8 mm inner diameter, 30 cm long quartz tube 10 into the aluminum stopper 9 so that the droplet reaches the center of the furnace 11, and the end and the tip of the sprayer stopper Tygon tube (7). ). At the bottom of the quartz tube 10, a collector 13 made of Pyrex glass with an inner diameter of 45 mm and a length of 7 cm is clogged to collect powder from the pyrolysis of droplets passing through the furnace 11 at the bottom of the furnace. The ring was used to connect to the aluminum connector 12. A bubbler filled with distilled water by connecting a Tygon tube (7) with a branch (reaction gas outlet 14) having an inner diameter of 4 mm and a length of 15 mm (reaction gas outlet 14) in the middle of the wall of the collector 13 to discharge the decomposed gas and the carrier gas. bubbler) 15.

Preparation Example 1 Preparation of 0.1 M Mixed Solution of Zinc Nitrate and Gallium Nitrate

In a 100 mL volumetric flask, 1.894 g (0.01 mol) of zinc nitrate and 5.115 g (0.02 mol) of gallium nitrate are accurately weighed, and the secondary distilled water is filled to about half the volume using a graduated cylinder. The volumetric flask was scaled correctly by dissolving and adding secondary distilled water. Subsequently, the mixture was further stirred for about 30 minutes with a magnetic stir bar to prepare 100 mL of a uniform 0.1 M mixed aqueous solution.

Preparation Example 2 Preparation of 0.3 M Mixed Solution of Zinc Nitrate and Gallium Nitrate

100 mL of a uniform 0.3 M aqueous solution was prepared in the same manner as in Preparation Example 1, except that 5.681 g (0.03 mol) of zinc nitrate and 15.344 g (0.06 mol) of gallium nitrate were used.

Preparation Example 3 Preparation of 0.05 M Mixed Solution of Zinc Nitrate and Gallium Nitrate

100 mL of a uniform 0.05 M mixed aqueous solution was prepared in the same manner as in Preparation Example 1, except that 0.947 g (0.005 mol) of zinc nitrate and 2.56 g (0.01 mol) of gallium nitrate were used.

Example 1

100 mL of the 0.1 M mixed aqueous solution prepared in Preparation Example 1 was put into a dropping funnel attached to a vibrator container, and the solution was dropped to about 5 cm above the vibrator, and oxygen was added to 30 sccm (standard cubic centimeters per minute, cm). ³ / min). The temperature of the furnace was previously raised to 1100 ° C. and controlled by an error of ± 10 ° C. In order to maintain the liquid level of the mixed aqueous solution of zinc nitrate and gallium nitrate on 5 cm of the vibrator while spraying was continued, the aqueous solution was dropwise added using a dropping funnel from time to time. After the reaction was completed, the temperature of the furnace was lowered to room temperature, and the zinc galliumate powder formed by separating the quartz tube from the furnace was collected.

Typical ZnGa ₂ O, including the main peak we attributed to 2θ in X-ray diffraction of the produced gallium acid zinc powder to 10 to 70 ° which is changed within a range that results 2θ confirm crystallinity _{35.6 ° ZnGa 2 O 4 (311} ) _Four powder peaks were observed, and no phases of zinc oxide (ZnO) or gallium oxide (Ga ₂ O ₃ ) were detected. In addition, the powder was analyzed by X-ray photoelectron spectroscopy to confirm that the ratio of zinc and gallium was 1: 2 within the error range of this method. In the scanning electron micrograph of the powder, the formed ZnGa ₂ O ₄ powder was spherical and slightly hollowed out. I could see that it is in the form.

In addition, the size of the powder particles showed a narrow distribution of 0.1 to 2 ㎛ ㎛, the average particle size was about 0.5 ㎛. In the photoluminescence spectrum of the powder, peaks with a wide band in the region of 380 to 560 nm with a maximum at 480 nm were observed.

Example 2

100 mL of the 0.05 M mixed aqueous solution prepared in Preparation Example 3 was subjected to ultrasonic spray pyrolysis under the same conditions as in Example 1 to prepare zinc galliumate powder. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron micrograph of the prepared zinc galliumate powder were the same as in Example 1. FIG. 2 shows the X-ray diffraction pattern (top) of zinc galliumate powder prepared in Example 2 and the standard X-ray diffraction pattern (bottom) of zinc galliumate, confirming that peaks of typical ZnGa ₂ O ₄ powders are observed. Can be.

In addition, the size of the powder particles showed a narrow distribution of 0.1 to 1 ㎛ ㎛, the average particle size was about 0.3 ㎛. In the photoluminescence spectrum of the powder, peaks with a wide band in the region of 380 to 560 nm with a maximum at 480 nm were observed.

Example 3

100 mL of the 0.3 M mixed aqueous solution prepared in Preparation Example 2 was subjected to ultrasonic spray pyrolysis under the same conditions as in Example 1, except that pyrolysis was performed at 900 ° C. to obtain zinc galliumate powder. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron micrograph of the prepared zinc galliumate powder were the same as in Example 1.

In addition, the size of the powder particles showed a narrow distribution of 0.2 to 2 ㎛ ㎛, the average particle size was about 1 ㎛. In the photoluminescence spectrum of the powder, peaks with a wide band in the region of 380 to 560 nm with a maximum at 480 nm were observed.

Example 4

100 mL of the 0.3 M mixed aqueous solution prepared in Preparation Example 2 was subjected to ultrasonic spray pyrolysis under the same conditions as in Example 1, except that compressed air was used as a carrier gas to prepare zinc galliumate powder. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron micrograph of the prepared zinc galliumate powder were the same as in Example 1. Figure 3 shows the X-ray diffraction pattern of the zinc galliumate powder prepared from Example 4, Figure 4a and 4b is a scanning electron micrograph of the zinc galliumate powder prepared from Examples 2 and 4, respectively, of the mixed aqueous solution It can be seen that the higher the concentration, the larger the particle size of the prepared powder.

In addition, the size of the powder particles showed a narrow distribution of 0.2 to 2 ㎛ ㎛, the average particle size was 1 ㎛. In the photoluminescence spectrum of the powder, peaks with a wide band in the region of 380 to 560 nm with a maximum at 480 nm were observed.

Example 5

Ultrasonic spray pyrolysis of 100 mL of the 0.3 M mixed aqueous solution prepared in Preparation Example 2 was performed under the same conditions as in Example 1 to prepare zinc gallium sulfate powder, followed by flowing a nitrogen gas containing 5% by weight of hydrogen gas. The zinc powder was reduced at 900 ° C. for 7 hours. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron micrograph of the prepared zinc galliumate powder were the same as in Example 1.

In addition, the size of the powder particles showed a narrow distribution of 0.2 to 2 ㎛ ㎛, the average particle size was 1 ㎛. 6A and 6B are photoluminescence spectra of zinc galliumate powders prepared from Examples 4 and 5 (addition of reduction treatment), respectively, and the reduction powder was observed to be about 5 times higher in strength than the untreated powder.

Example 6

After adding 0.6 wt% of manganese nitrate (Mn (NO ₃ ) ₂ ) to the 0.3 M mixed aqueous solution prepared in Preparation Example 2, 100 mL of the mixed aqueous solution was ultrasonically spray pyrolyzed under the same conditions as in Example 1 to give gallium acid. Zinc powder was prepared. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron micrograph of the prepared zinc gallate powder were the same as in Example 1, and the presence of a small amount (less than 1% by weight) of Mn in the powder by X-ray photoelectron spectroscopy. 5a and 5b (Mn 2p high resolution spectra).

In addition, the size of the powder particles showed a narrow distribution of 0.2 to 2 ㎛ ㎛, the average particle size was 1 ㎛. 7A and 7B are photoluminescence spectra of zinc gallium oxide powders prepared from Examples 4 and 6 (Mn incorporation), respectively, with Mn incorporating a maximum at 507 nm and narrow bands in the region of 500 to 515 nm. With peaks were observed.

According to the ultrasonic spray pyrolysis method according to the present invention, it is possible to uniformly mix the reactants used in the production of zinc galliumate, allowing the introduction of the admixture and the control of the particle size while suppressing the generation of by-products, gallium which is a low voltage phosphor for FED Zinc zinc may be prepared in a high purity powder form.

Claims (5)

Zinc nitrate (Zn (NO ₃ ) ₂ ) and gallium nitrate (Ga (NO ₃ ) ₃ ) are dissolved in water so that Zn / Ga is in the range of 0.4 to 0.5, and the resulting aqueous solution is sprayed using an ultrasonic vibrator. A method of producing zinc galliumate (ZnGa ₂ O ₄ ) powder, comprising transporting a sprayed mist together with a carrier gas to a furnace and pyrolyzing at 900 to 1200 ° C. The method of claim 1, And adding 0.1 to 1% by weight of manganese nitrate (Mn (NO ₃ ) ₂ ) of zinc nitrate to the mixed aqueous solution of zinc nitrate and gallium nitrate. The method of claim 1, And further reducing the pyrolysis with a nitrogen gas containing hydrogen gas. The method of claim 1, The carrier gas is air or oxygen. The method of claim 1, The concentration in the aqueous solution of zinc nitrate and gallium nitrate is 5 to 20% by weight.