JPS5924729B2 - Method for producing crystalline gallium oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing crystalline gallium oxide.

Crystalline gallium oxide is particularly important as a raw material for phosphors, but it is difficult to obtain it with good purity and crystallinity, and until now only very complicated manufacturing methods have been developed. , and had many shortcomings.

The main conventional production methods include 1) a method in which carbon dioxide gas is blown into an alkaline solution of gallium salt to gradually hydrolyze it and precipitate gallium metahydroxide (J,
Bohn and G, KahanpZ.

anorg, allg Chem, , 238. 35
0 (1958)).

2) A method of neutralizing an ammonia aqueous solution by adding an ammonia aqueous solution to a gallium chloride aqueous solution, and then leaving it for one week or more to precipitate and separate gallium metahydroxide (J, Bohn and
G, KahanpZ, anorg, allg.

Chem, 38, 350 (1958)).

3) Add an ammonia aqueous solution to the gallium chloride aqueous solution to neutralize it, and then place it in an autoclave.

Method of treatment at water vapor pressure of 70 to 80 atm and 290°C for 4 hours ()LB, We 1sen and W, 01
M1ll-igan, J., Phys, Chem.
42, 673 (1938)).

However, method 1) only requires a long time in the process itself, and N
Alkali metal ions such as a'' and + are mixed in, and their removal is generally very difficult.

When the above-mentioned precipitate mixed with alkali is then roasted to form gallium oxide, its melting point is lowered, so that it tends to form sintered lumps, and further pulverization is required.

It is presumed that this will also have an adverse effect on the production of phosphors.

Method 2) is a method in which an aqueous ammonia solution is added to an aqueous solution of gallium salt to neutralize it (hereinafter abbreviated as the neutralization method).
The viscosity becomes extremely high in the range of 7J3, resulting in the formation of a gel-like precipitate of hydrous oxide, resulting in a viscous solution.
This is likely due to reasons such as difficulty in stirring during heating and ripening, and uneven heat transfer within the precipitate, which tends to result in insufficient production of metahydroxide.

Therefore, when the precipitate mentioned above is roasted to form an oxide, a sintered lump is partially formed, and further pulverization is necessary, so that contamination with impurities is unavoidable.

In addition, since chloride is used as a raw material, it is unavoidable that chloride is mixed into the hydroxide obtained.
Partial loss occurs by volatilization as C13 (boiling point 215°C).

In addition to the drawbacks of method 2), method 3) has other decisive drawbacks, such as requiring a reaction apparatus at high temperature and pressure.

An object of the present invention is to eliminate the above drawbacks and provide a method for producing crystalline gallium oxide with simple operation and high purity.

In order to achieve this objective, the present invention first investigated the conditions for precipitation of gallium hydroxide, and added gallium salt to an ammonia aqueous solution using the conventional neutralization method in which an ammonia aqueous solution is added to an aqueous solution of a gallium salt. The method of adding an aqueous solution of
The value fluctuates slowly (see curve B in Figure 1), and the viscosity of the aqueous solution during neutralization is as low as approximately 100% (see Figure 2), which greatly affects the properties of the precipitate that is generated. In fact, we experimentally found that

As a result of further intensive research based on the above-mentioned discoveries of the present invention, we have found that by regulating the pH at the time of precipitate formation and the salt concentration when gelatinizing gallium hydroxide during the reverse neutralization method, efficiency can be improved. It was discovered that well-crystalline gallium metahydroxide can be obtained, and the precipitate obtained in this way does not lose its crystalline form during the subsequent roasting process, so there is no need for pulverization. Chiru.

That is, in the present invention, the ammonia aqueous solution is stirred.

To this, add an aqueous solution of gallium nitrate with pH 0.5 to 1.4 to the ammonia aqueous solution so that the pH value is in the range of 8 to 9.5, and then add water if necessary to adjust the concentration of ammonium nitrate in the aqueous solution. After adjusting the weight to 190g/7 or less, the mixture was kept at a temperature of 80°C or higher for 2 hours or more while stirring lightly.

It consists of separating and roasting the precipitate that is produced.

The present invention will be explained in detail below.

As the gallium salt used in the method of the present invention, an aqueous solution of gallium nitrate is used for the purpose of avoiding contamination with impurities, and this is added to an ammonia aqueous solution of an appropriate concentration.

The main idea is to produce gallium metahydroxide by the reverse neutralization method.

The concentrations of the gallium nitrate and ammonia aqueous solution used here are not particularly limited, but it is better to use too high a molar concentration for gallium nitrate and 2 to 4 molar concentration for the ammonia aqueous solution. 4-10 molar concentration (NH
3 - about 4 to 18.4% by weight).

Even if the ammonia aqueous solution is thinner than the above, it is not preferable because it reduces the particle size of the formed precipitate.

PI of aqueous solution when performing reverse neutralization method (value is 8 to 9.5
Adjust the mixing ratio of the rainwater solution so that

That is, an equivalent amount of gallium nitrate aqueous solution is added to the ammonia aqueous solution after pre-neutralizing with an ammonia aqueous solution to a pH of 0.5 to 1.4.

Pre-neutralized gallium nitrate is used to minimize the temperature change due to the heat generated during one reaction (according to illegal regulations,
This is to avoid unevenness in concentration, temperature, etc. in the mixed aqueous solution.The reason why the northern limit of pH is set at 1.4 is that gallium hydroxide This is because the aqueous solution becomes cloudy due to precipitation.

The reversely neutralized aqueous solution is then strengthened with water if necessary to adjust the concentration of ammonium nitrate to 190 g/d or less, preferably 170 g/d or less, but before that, 10 to 3 g/d is added.
It is preferable to ripen the precipitate for about 0 minutes in advance and then dilute it with water in order to make the particle size of the metahydroxide produced uniform.

The aqueous solution with adjusted concentration of ammonium nitrate was then mixed with 8
2 at a temperature below 0°C, preferably above 90°C, with gentle stirring.
Hold for more than an hour.

After producing a precipitate of gallium metahydroxide, it is filtered, washed, dried, and further roasted to obtain crystalline gallium oxide.

In the present invention, the ammonia aqueous solution has a pH of 0.5 to 1.
The reason why we adopted the reverse neutralization method of adding the gallium nitrate aqueous solution in step 4 so that the pH value was 8 to 9.5 was adopted.

As mentioned earlier, this is to lower the viscosity of the aqueous solution during neutralization to allow the hydroxide production reaction to proceed smoothly.
If the range of H is other than the above, it is from Ga(OH)3 to αG.
This is because the transformation behavior (gelatinization rate) to a00H becomes poor.

Next, the concentration of gallium nitrate and the concentration of ammonia aqueous solution are preferably set to 2 to 4 mol and 2.4 to 10 mol, respectively, in order to make the particle size of gallium metahydroxide uniform on the larger side. However, if the average particle size of the precipitate is outside this range, for example, 2 microns or less, the filterability etc. will deteriorate and this is not preferred in practice.

In addition, the concentration of ammonium nitrate aqueous solution at the time of precipitation of gallium metahydroxide is 190 g/l or less, preferably 170 g/l or less.
The reason for setting it below g/l is that if the concentration is higher than this, the gelatinization rate of the precipitate will decrease, and therefore the filtration rate of the precipitate will be extremely deteriorated.

Next, the reason why the precipitation aging is carried out at 80° C. for 2 hours or more is because the gelatinization rate of the precipitate should be 95% or higher if 90% or more is required.

If the gelatinization rate is 90% or less, some of the crystals will agglomerate in the next roasting process, making it necessary to grind them.

Incidentally, roasting can be carried out at 700 to 1000°C for several tens of minutes to one hour.

According to the method of the present invention, gallium metahydroxide that is crystalline and has a relatively uniform particle size can be efficiently obtained, and even when roasted, it has a characteristic shape (diamond-shaped cross section, acicular crystals).
It has the advantage that there is no need for a pulverization process because it does not break down.

In addition, other advantages of the present invention are that the manufacturing process is simple and the crystals have a good shape, so they have good sedimentation properties and filtration P.
The advantages include that the unit operation time is shorter, and that a product of high purity can be obtained because it does not require pulverization of crystals.

Examples will be described below.

Experimental example 1 Weigh out 40g each of metallic gallium and weigh 62g each.
% by weight of nitric acid; 250-75 mlJ of gallium nitrate with a 2.3-7.7 molar concentration was prepared by dissolving it.

A 2+1 (Conc, NH4OH soil water) ammonia aqueous solution was added to this to adjust the pH to 1.0, and water was further added to prepare gallium nitrate having a 0.9 to 4 molar concentration.

Next, separate from this, prepare 2007 rL/l of ammonia aqueous solution containing 18% by weight of NH40H, and while stirring this lightly, add each of the above gallium nitrate aqueous solutions at room temperature.
Calories were added so that H was 9.0, and after aging for 30 minutes, water was added to make the total amount of water 900 mlJ each, and then heated to maintain the liquid temperature at 95°C and gently stirred for 30 minutes. After holding for a period of time and filtering, washing and drying the formed precipitate, 50% of the precipitate is measured using a light transmission particle size distribution analyzer (sedimentation method).
The sectional distribution particle size was measured.

The results are shown in FIG. As can be seen from Figure 3, when the concentration of gallium nitrate is 2 to 4 mol, the crystal grain size is approximately 3 μm.
But.

At lower concentrations, the particle size decreased significantly.

If the concentration of gallium nitrate is 4 mol or more, the particle size tends to become larger, but this is not preferable because salt precipitation is observed during neutralization.

Experimental Example 2 Add a small amount of ammonia aqueous solution to a 4.8 molar concentration gallium nitrate aqueous solution to prepare gallium nitrate with a pH of 1, 0, 2, and 9 molar concentrations, and divide this and add each to an ammonia aqueous solution with a predetermined concentration. Add it at room temperature so that the pH value becomes 9.0, stir gently for about 30 minutes, then add water and add 2.
The mixture was diluted twice and kept at 95°C for 3 hours with gentle stirring.

Next, the generated precipitate was filtered, washed, and dried, and then the 50% area distribution particle size was measured in the same manner as in Experimental Example 16. The results are shown in FIG.

As can be seen from Figure 4, the ammonia concentration is 4% by weight (N
H40H = 8.2% by weight = -2.4 mol) or more, particles with a large particle size were obtained.

Example 1 To 450 g of gallium oxide, a first class reagent, 2.51 nitric acid (62% by weight) and 300 mL of water were added and dissolved by heating, and the mixture was further concentrated to a liquid volume of 750 mL to remove most of the free nitric acid. The mixture was evaporated and water was added to give a concentration of 11.

The gallium nitrate aqueous solution of 4 and 8 molar concentrations prepared in this way was separated into 6 portions of 12 om each, and added to it with NH40H.
A gallium nitrate aqueous solution having a pH of 1.0 and a concentration of 2.8 mol was prepared by adding 18% by weight of ammonia aqueous solution Fukaya 80m#.

Each of these was added to an ammonia aqueous solution to reach a predetermined P level.
NI (40H = 18.1% by weight (5
, 2 mol) of ammonia aqueous solution at room temperature, stirred gently for 30 minutes, and then diluted to 2 times with water (approximately 900 mA).
Maintain at 95°C for 3 hours with gentle stirring.

The generated precipitate was filtered, washed and dried.

After drying, it was roasted at 950°C for 1 hour, and the properties of the obtained crystals were examined.

The results are shown in Table 1 and the properties of the precipitate are shown in Figure 5.

As is clear from Table 1 and Figure 5, the pH during treatment was 8.
In addition, when the gelatinization rate was 9.5 or less, excellent gelatinization rate and average particle size were obtained, and the more gelatinization progressed, the better the properties such as the settling rate of the precipitate.

FIG. 5 shows the standing time and the sedimentation rate of the precipitate.

Example 2 The concentration of gallium nitrate during the production of gallium metahydroxide was
20-57.5 g/11 (Ga(N
Oa) 3''(73.7~210.9g/A'),
PH9.0, ammonium nitrate concentration 149-210
Processed in the same manner as in Example 1 except that g/11 was used,
The filtration rate of the obtained precipitate was examined.

The filtration device uses a Nutsche covered with /165B filter paper.
By suction filtration method.

The results are calculated using the concentration of gallium and ammonium nitrate and pH.
Table 2 shows the relationship between the filtration rate and the filtration rate.

As is clear from Table 2, it has little to do with the concentration of Ga; if the concentration of ammonium nitrate is too high, the filtration performance deteriorates, and when the concentration is 170g713 or less, the sedimentation property is the best.
Filtration speed was fast.

On the other hand, the concentration of gallium does not have a very strong influence, but
30-50 g/1 (Ga (NOa) as a
0.43 to 0.72 mol) was the best.

Example 3 In the same manner as in Example 1, 200 ml of a gallium nitrate aqueous solution with a pH of 1.0 and a concentration of 2.9 mol was prepared, and this was added to NH4
Stir and add to 200 mil of ammonia aqueous solution containing OH=18.1% by weight (approximately 5.2 mol).

After stirring gently for 30 minutes, water was added to bring the total liquid volume to 900 m7.

The pH of the aqueous solution is 9.1. Ga is 44.6g, #(0,
64 mol) NH4NO3152g / 13 (1,
9 mol), which formed a gel-like state, was vigorously heated at a constant temperature of 80 to 95°C while stirring gently, and a small amount of the precipitate formed was removed every hour, filtered, washed, After drying, the transformation behavior from Ga(OI()3 to αGa0OH) was estimated by a thermobalance method.

The results are shown in Table 3. As is clear from Table 3, the treatment time is at least 2 hours, and the treatment temperature is 90°C if necessary.
℃ or higher, and at 80° C., even if the treatment time was 2 hours, the gelatinization rate could not be said to be sufficient.

This gelatinization rate is desirably 95% or more, and if it is less than 90%, pulverization is required after roasting.

[Brief explanation of drawings]

Figure 1 shows the change in pH due to the constant neutralization method and reverse neutralization method. Figure 2 shows the relationship between PH and viscosity in the regular neutralization method and reverse neutralization method, Figure 3 shows the relationship between the Ga (N Oa )s concentration and the average particle size of the precipitate, and Figure 4 shows the relationship between the ammonia concentration and the precipitate. Figure 5 shows the settling time and sedimentation volume (height), respectively.

Claims (1)

[Claims] I Add a gallium nitrate aqueous solution with pH 0.5 to 1.4 to an ammonia aqueous solution while stirring so that the pH value becomes 8 to 9.5, and then add it so that the concentration of ammonium nitrate in the aqueous solution becomes 190 g or less. A method for producing crystalline gallium oxide, which comprises adjusting the temperature to 80° C. or higher for 2 hours or more while stirring, and then separating and roasting the formed precipitate.