JP2002121021A - Rare earth hydroxide, method for producing the same, and sintered body added with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth element hydroxide that rarely changes in rare earth element content with time, has little crystallization water and adherent water, and is easily dispersed in a ceramic main material. SOLUTION: A general formula Ln (OH) ₃ (Ln is Y, L
a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Yb, and Lu are at least one rare earth element). The particle size of the crystallite as determined by X-ray diffraction is 40 nm or less, and 300 pp of chlorine.
m and a nitrate ion of 100 ppm or less. Theoretic loss% at 1000 ° C for 1 hour
And the average particle diameter of the secondary particles obtained by agglomeration of the crystallites is preferably 0.1 μm or more and 2 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electronic ceramics and S
The present invention relates to an additive for structural material ceramics such as i ₃ N ₄ and AlN.

[0002]

2. Description of the Related Art Rare earth elements are used as additives for electronic ceramics such as dielectric filters and ceramic capacitors, and structural ceramics such as Si ₃ N ₄ and AlN. When lanthanum or neodymium is added, it is generally used in the form of an oxide. Oxides of lanthanum and neodymium are hygroscopic, and partly change to hydroxides depending on the storage state, and the contents of lanthanum and neodymium change with time. Therefore, it is necessary to measure the content again each time it is added.

As a solution to the problem that the rare earth oxide changes with time due to moisture absorption, there is a method using a rare earth hydroxide instead of the oxide. Generally, the rare earth hydroxide is produced by a production method called a wet method. The wet process is generally performed by reacting a rare earth aqueous solution (for example, a rare earth nitrate solution / a rare earth chloride solution) with an alkali solution (for example, aqueous ammonia / sodium hydroxide) at a temperature from room temperature to a high temperature (about 80 ° C.), A hydroxide with good filterability is obtained. After the filtration, the product is sufficiently washed with water, and then dried at a temperature of 200 ° C. or less (Japanese Patent Application Laid-Open No. 62-5928
JP, JP-A-09-188515). In the rare earth hydroxide obtained by the wet method, the crystallites as primary particles are amorphous, and the particle size cannot be measured by X-ray diffraction. The secondary particles are acicular, have a strong cohesive force, and a large particle size.

[0004] In the above-cited publications, the secondary particle diameters are 2 to 100 µm and 5 to 100 µm, respectively. Although the filterability is improved due to the large particle size, pulverization with a pulverizer, a jet mill or the like is required. Even if it is finely ground to some extent by pulverization, it is not easy to disperse it in the ceramic main material due to strong cohesion. In addition, since the primary particles are indefinite, cleaning properties are poor, so that nitrate ions, chlorine, ammonia, and sodium tend to remain. Residual nitrate ion, chlorine and ammonia become N
It occurs as O _X or chlorine gas, to damage the furnace body, which is not preferable for the environment. Japanese Patent Application Laid-Open No. 11-349376 discloses that Sm ₂ O ₃ having a hydroxyl group on its surface is good as a raw material for a microwave resonator / filter. This is presumably because the commercially available hydroxide produced by the wet method has improved hygroscopicity, but has the above-mentioned problems. Therefore, by ball milling rare earth oxides in water,
It has been proposed to improve the problem by attaching a hydroxyl group only to the surface, but it has not been possible to solve all of the above problems.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a rare earth element having a small change with time,
It is not necessary to measure the content every time it is added, it has little water of crystallization and adhered water, is suitable for ceramics that dislike moisture, and is easily dispersed in the main ceramic material. It is an object to provide a sintered body to which is added.

[0006]

[MEANS FOR SOLVING THE PROBLEMS]
The rare earth hydroxide of the present invention has a general formula Ln (OH) _Three
(Ln is Y, La, Ce, Pr, Nd, Sm, Eu,
Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu
One or two or more rare earth elements)
X-ray diffraction method has a crystallite particle size of 40 nm or less;
Chlorine 300ppm or less, nitrate ion 100ppm or less
There is a feature. 1000 ° C, 1 hour burning loss
Is within ± 2% of the theoretical value%, and
Has an average particle size of 0.1 μm or less
It is preferably 2 μm or less. In particular, the general formula Ln
(OH)_ThreeIs equal to Nd, the color difference value L^*a^*b^*Is L
^*Is 90 or more and 95 or less, a^*Is 3 or more and 6 or less, b^*Is -1
More preferably, it is 0 or more and -5 or less. How to make it
The method is as follows: 1. 1 mole of rare earth oxide and 1 mole of rare earth oxide.
5 mol or more and 3 mol or less of water or steam at 30 ° C. or more,
Mix at 200 ° C. or less for 1 to 24 hours. The resulting
The rare earth hydroxide of the present invention is a dielectric filter or
Used as an additive for ceramic capacitors.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that primary particles (also called single crystal particles and crystallites) and secondary particles (agglomerated particles) are fine, the particle size distribution is sharp, and the amount of crystallization water and attached water is small. They have found that rare earth hydroxides are suitable as additives for ceramics, and have completed the present invention based on this finding. When a rare earth hydroxide is used as an additive for electronic ceramics such as a dielectric filter or a ceramic capacitor, the main material of the electronic ceramic is, for example, barium titanate, and the rare earth reacts titanium oxide with the rare earth hydroxide. Then, a rare earth titanate is prepared and added in the form of a rare earth titanate.

The particle diameter of barium titanate or titanium oxide is about 0.1 μm to 0.5 μm. It is preferable that the rare earth hydroxide added to the ceramic main material is dispersed so as to cover the surface of the main material particles. The primary particle size of the rare earth hydroxide is preferably about 40 times or less, which is about 1/10 of the main material particle size. In the present invention, the measurement of the crystallite particle size as the primary particle employs a method performed by the Scherrer method of X-ray diffraction. As another measurement method, there is a method of directly taking a picture of a crystallite with a transmission electron microscope and measuring from the picture, but it is troublesome and is not suitable for quality control of a product. When the crystallite size is larger than 40 nm,
It cannot be dispersed so as to cover the surface of the ceramic main material particles. In the present invention, when the crystallite diameter is in the range of 40 nm or less, the specific surface area (BET) is preferably 4 to 25 m ² / g, and more preferably 6 to ²⁰ m ² / g.

The conventional wet method uses a rare earth nitrate solution
Since a rare earth chloride solution is used, chlorine and nitric acid easily remain in the product. The rare earth hydroxide proposed this time has a small amount of residual chlorine and nitric acid. Specifically, it is easy to reduce the chlorine to 300 ppm or less and the nitrogen to 100 ppm or less. The ignition loss of the rare earth hydroxide having no crystallization water and no attached water at 1000 ° C. for one hour is as follows. Theoretical value of burning loss (%) = ｛1- (rare earth oxide molecular weight (LnO _x ) / rare earth hydroxide molecular weight (Ln (O
H) ₃ )｝ × 100 Note that x differs depending on the type of rare earth element, and Y, La,
Group 3A from Nd to Gd, Dy to Lu has x = 1.5, C
e is x = 2, Pr is x = 11/6, and Tb is x = 7/4.

For example, 1000 yttrium hydroxide
C., 1 hour of loss on ignition (theoretical value) is 19.3%. Similarly, the theoretical value of lanthanum hydroxide 14.2%,
The theoretical value of neodymium hydroxide is 13.8%, and the theoretical value of lutetium hydroxide is 11.95%. Since the measurement error of the loss on ignition at 1000 ° C. for 1 hour is about ± 1%, the loss on ignition at 1000 ° C. for 1 hour of the rare-earth hydroxide without crystallization water and attached water is ± 2% of the theoretical value (%). It is necessary to be within. The fact that the loss on ignition is smaller than -2% with respect to the theoretical value (%) means that a part of unreacted oxide remains, and depending on the storage state, it changes over time due to moisture absorption. The fact that the ignition loss is larger than the theoretical value (%) by more than 2% indicates that there is water of crystallization / adhered water or that other compounds such as chlorine and nitric acid are mixed.

[0011] Theoretically, if the crystallite diameter and the secondary particle diameter are the same, the particles are monodispersed, and it is considered easy to add them to the main material. However, in reality, when the crystallite particle size is as small as 40 nm or less, it is difficult to be monodisperse and stable. In the case of fineness, the bulk density becomes too small, making it difficult to handle. Therefore, without grinding, it is preferred that the primary particles is several to several tens agglomerated secondary particles, specifically, the average particle diameter D ₅₀ of the secondary particles is 0.1μm or more, 2μm or less Good. Here, the average particle diameter D ₅₀ of the secondary particles is obtained by performing an ultrasonic dispersion treatment at 40 W for 3 minutes and then measuring the particle size distribution by a laser diffraction method.

If the average particle size of the secondary particles is less than 0.1 μm, the bulk density becomes too small, and the bulk becomes large, making it difficult to handle. If the average particle size of the secondary particles exceeds 2 μm, the particle size is large, and it is difficult to disperse the secondary particles in the main ceramic material.
Secondary particle average particle diameter D ₅₀ 0.1μm or more in the case of 2μm or less, the bulk density is 0.15~0.5g / cm ^3.
Incidentally, D _n is the particle diameter n% of the particles have a D _n smaller diameter. Crystallites are dispersed in the main ceramic material,
It is preferable that not only the secondary particles are fine, but also the particle size distribution is sharp. Specifically, after performing an ultrasonic dispersion treatment at 40 W for 3 minutes, in a particle size distribution measurement by a laser diffraction method, a dispersion index = (D ₉₀ −D ₁₀ ) / (D ₉₀ + D ₁₀ ) is 0.1.
It is preferably 6 or less.

For example, in the case of neodymium as a rare earth, neodymium hydroxide has a unique blue-violet color. Neodymium oxide has a light blue color, and neodymium chloride and neodymium nitrate have a purple-red color. If unreacted neodymium oxide, neodymium chloride or neodymium nitrate is mixed, the color changes and the color difference value L ^* a ^* b ^* changes. The color difference value changes even when a large amount of transition metals such as iron group are mixed. In particular, neodymium hydroxide of the present invention is a mixture of neodymium oxide, neodymium chloride and neodymium nitrate, and transition metals such as iron group and the like have 50 ppm or less of color difference value L ^* a ^* b ^* of neodymium hydroxide. L ^*
Is 90 or more and 95 or less, a ^* is 3 or more and 6 or less, and b ^* is -10.
The range was at least -5.

The process for producing the rare earth hydroxide is simple, unlike the conventional wet process. A rare earth hydroxide is obtained by gradually reacting the water necessary for the rare earth oxide to change to a hydroxide. Specifically, 30 ° C
As described above, while maintaining the temperature at 200 ° C. or less, the average crystallite diameter is 10 to 80 nm, and the rare earth oxide which is an aggregated particle having an average particle diameter of 0.1 to 10 μm is 1.5 mol per 1 mol of the rare earth oxide At least 3 mol or less of water or steam is gradually added and mixed. The reason why water or water vapor is gradually added is that the reaction occurring here is an exothermic reaction, so that it is dangerous to react at once. Temperature is over 30 ℃, 200 ℃
The reason why the range is as wide as follows is that the range differs depending on the rare earth element.

In particular, lanthanum oxide is relatively reactive,
Although the reaction occurs even at about 30 ° C., the reaction takes a long time at a low temperature. Rare earth oxides other than lanthanum require a temperature of 70 ° C. or higher. In particular, the element called heavy rare earth is 10
A temperature of 0 ° C. or higher is required. In any case where any of the rare earth elements is used, if the temperature exceeds 200 ° C., oxygen of water or oxygen in the atmosphere and a hydroxide cause an oxidation reaction, and the oxide hardly changes to a hydroxide, which is not preferable. in this way,
Because oxides are reacted at high temperature in pure water, Cl,
Impurities such as NO ₃ can be reduced. As processing time,
Preferred is 1 to 24 hours.

The present invention is suitable as an additive for rare earth sintered bodies, particularly electronic ceramics such as dielectric filters and ceramic capacitors, and structural ceramics such as Si ₃ N ₄ and AlN. dielectric filter used is using _{BaO · Ln 2 O 3 · Ti} 2 O 3 -based material. Here, Ln is Y, La, Ce, P
r, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
At least one of r, Tm, Yb, and Lu is a rare earth element. Preferably La, Ce, Pr, Nd, Sm
Is good.

To manufacture a dielectric filter, barium carbonate / titanium oxide and a rare earth hydroxide are wet-mixed in a ball mill, dehydrated, dried, and calcined in the atmosphere. An organic binder is added to the resulting component materials, wet-mixed again with a ball mill, and spray-dried. The resulting granulated powder is molded, sintered,
Process and finish into a dielectric filter. Generally, an oxide is used as the rare earth compound. However, in the present invention, by using the rare earth hydroxide proposed in the present invention, the mixing time and the sintering temperature can be reduced,
Improvements in characteristics can also be expected.

[0018]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these. [Example 1] Neodymium oxide (average crystallite diameter 40 nm,
After placing 164 g of average particle size (5 μm) and 27 g of pure water in a closed pressure vessel having a volume of 1 liter and thoroughly mixing,
To 120 ° C. for 4 hours to obtain neodymium hydroxide. The particle size distribution of the resulting secondary particles of neodymium hydroxide was measured by a laser diffraction method after an ultrasonic dispersion treatment of 40 W × 3 minutes. D ₁₀ = 0.56 μm, D ₅₀ = 0.88
μm, D ₉₀ = 1.43 μm. The dispersion index is 0.
43.

The crystallite size is determined by the X-ray diffraction Scherre.
It was 30 nm as determined by the r method. Specific surface area (B
ET) was 10.9 m ² / g (JIS R 1626). The loss on ignition at 1000 ° C. for 1 hour was 13.8%. The bulk density was 0.31 g / cm ³ . The color difference value (JIS Z 8729) is a colorimeter, and L ^* is 91.
7, a ^* was 4.74 and b ^* was -6.9. Chlorine was measured by a turbidimetric method, and nitrogen was measured by a combustion-IR method. Chlorine is 100
ppm and nitrate ion were 50 ppm. The iron group element was 12 ppm as measured by an ICP method.

Neodymium hydroxide, barium carbonate and titanium
Tanoic acid is BaO · Nd_TwoO_Three・ 5Ti _TwoO_ThreeIn total
Weigh to 300 g. Add 300 g of water,
After 12 hours wet mixing in a mill, the whole amount was 100 ° C,
Dry for 24 hours. Further, at 800 ° C. for 2 hours in the atmosphere
Calcined on hold. 450 g of water was added to the obtained powder,
0.6g of MC (carboxyl methyl cellulose) is added
After wet mixing with a ball mill for 12 hours, spray the entire amount
Dried. The obtained granulated powder is placed in a 4 mm
9.03MPa (500kg / cm^Two). Big
It was sintered at 1350 ° C. for 4 hours in air. Obtained sintered body
Was processed into a size of 15 mmφ × 5 mmt. 2GHz
Dielectric constant ε (20 ° C) at the frequency of
Asked from. From the measured values at 20 ° C and 80 ° C, the temperature of the dielectric constant
The coefficient τ was determined. Relative permittivity ε is 80, temperature coefficient of permittivity
τ was −10 ppm / ° C.

[Comparative Example 1] 0.5 L of an aqueous neodymium chloride solution (neodymium concentration: 0.1 mol / l) was placed in a 2 liter beaker, and while maintaining the temperature at 80 ° C, an ammonia aqueous solution (alkali concentration: 0.3 mol / l) Liter) 0.6
The liter was introduced in about 1 hour while stirring with a stirring blade at 300 rpm. Then, the mixture was filtered and washed with water, and the obtained cake was
It dried at 10 degreeC and 24 hours. The color difference values of the resulting neodymium hydroxide are as follows: L ^* is 87.4, a ^* is 6.6, and b ^* is -1.
0.4.

The particle size distribution of the secondary particles was measured by a laser diffraction method. D ₁₀ = 2.6 μm, D ₅₀ = 15.3 μm, D ₉₀ =
It was 85.3 μm. The dispersion index is 0.94.
An attempt was made to measure the crystallite particle size by the Scherrer method of X-ray diffraction, but the measurement was indeterminate and could not be measured. The specific surface area (BET) was 26 m ² / g. The loss on ignition at 1000 ° C. for 1 hour was 16.6%. The bulk density was 0.6 g / cm ³ . Chlorine was measured by a turbidimetric method, and nitrogen was measured by a combustion-IR method. Chlorine is 1000ppm, nitrate ion is 100ppm
Met. Further, the iron group element was measured by ICP method,
It was 0 ppm.

The metering resulting neodymium hydroxide and barium carbonate titanate to be 300g in total in a ratio of _{BaO · Nd 2 O 3 · 5Ti} 2 O 3. Add 300g of water,
After wet mixing in a ball mill for 12 hours, the total amount was 100
C. and dried for 24 hours. Furthermore, at 800 ° C.
Calcination with holding time. 450 g of water was added to the obtained powder, 0.6 g of CMC was added, and the mixture was wet-mixed with a ball mill for 12 hours, and then the whole amount was spray-dried. The obtained granulated powder was placed in a 20 mmφ mold at 49.03 MPa (500 kg /
cm ² ). It was sintered at 1350 ° C. for 4 hours in the atmosphere. The obtained sintered body was processed into a size of 15 mmφ × 5 mmt. Dielectric constant ε at a frequency of 2 GHz
(20 ° C.) was determined from an LCZ meter. 20 ℃ and 80 ℃
The temperature coefficient τ of the dielectric constant was determined from the measured value of. Relative permittivity ε
Was 78 and the temperature coefficient τ of the dielectric constant was −20 ppm / ° C.

Example 2 Samarium Oxide (Average Crystallite
174 g of pure water 3 with a particle size of 28 nm and an average particle size of 3.5 μm)
2 g in a 1 liter sealed pressure vessel
After mixing, keep at 20 ° C to 80 ° C for 4 hours
Thereby, samarium hydroxide was obtained. Hydroxide formed
The particle size distribution of the secondary particles of Malium was measured by the laser diffraction method.
Was. D _Ten= 1.12 μm, D₅₀= 1.82 μm, D₉₀=
3.03 μm. The dispersion index is 0.43.
The crystallite particle size was determined by the Scherrer method of X-ray diffraction.
However, it was 40 nm. Specific surface area (BET) is 1
2.8m^Two/ G. 1000 ° C for 1 hour
The amount was 13.1%. Bulk density is 0.19 g / cm^Three
Met.

Chlorine is measured by turbidimetry, and nitrogen is measured by combustion-IR method.
Specified. Chlorine is 60ppm, nitrate ion is 50ppm
there were. The resulting samarium hydroxide, barium carbonate and titanium
Acid to Ba_0.98Sm_0.02TiO _Three3 in total so that
Weigh to 00 g. Add 300g of water and add
After wet-mixing with a mill for 24 hours, 1.5 g of PVA was added.
After further mixing for 6 hours in a ball mill, the total amount was 10
It was dried at 0 ° C for 24 hours. The resulting dry powder is 20mmφ
With a mold, 49.03MPa (500kg / cm^Two)
Shaped. It was baked at 1200 ° C. for 4 hours in the air. Can
The sintered body was processed into a size of 15 mmφ × 5 mmt.
The measured breakdown voltage was 200 V.

Comparative Example 2 One liter of an aqueous samarium nitrate solution (samarium concentration: 0.2 mol / liter)
Oxalic acid aqueous solution 2 while stirring at 200 rpm at room temperature
L (oxalic acid concentration 0.2 mol / l) was added over 20 minutes, and after aging for 20 minutes, the mixture was filtered and washed with pure water. The obtained cake was baked at 800 ° C. in the atmosphere. The particle size distribution of the resulting samarium oxide was measured by a laser diffraction method. D ₁₀ = 1.1
2 μm, D ₅₀ = 3.26 μm, D ₉₀ = 5.17 μm. The dispersion index is 0.64. The crystallite size is X
When determined by the Scherrer method of line diffraction, 25 nm
Met. The specific surface area (BET) was 5.8 m ² / g. The loss on ignition at 1000 ° C. for 1 hour was 1.3%. The bulk density was 0.50 g / cm ³ .

Chlorine was measured by a turbidimetric method, and nitrogen was measured by a combustion-IR method. Chlorine was 50 ppm and nitrate ion was 50 ppm. The resulting samarium oxide, barium carbonate and titanic acid are converted to Ba _0.98 Sm _0.02 TiO ₃ for a total of 30.
Weigh to 0 g. After adding 300 g of water and wet-mixing with a ball mill for 24 hours, adding 1.5 g of PVA and further mixing with a ball mill for 6 hours.
C. and dried for 24 hours. The resulting dried powder was molded in a ²⁰ mmφ mold at 49.03 MPa (500 kg / cm ² ). It was baked at 1200 ° C. for 4 hours in the air. The resulting sintered body was processed into a size of 15 mmφ × 5 mmt. It was 170V when the breakdown voltage was measured.

Example 3 300 g of lanthanum oxide (average crystallite size 25 nm, average particle size 2.3 μm) and pure water 55
g was placed in a sealed pressure vessel having a volume of 1 liter, mixed well, and then kept at 90 ± 10 ° C. for 4 hours to obtain lanthanum hydroxide. The particle size distribution of the resulting secondary particles of lanthanum hydroxide was measured by a laser diffraction method in the same manner as in Example 1. D ₁₀ = 1.1 μm, D ₅₀ = 2.0 μm,
D ₉₀ = 3.3 μm. The dispersion index is 0.5. The crystallite particle size was 36 nm as determined by the X-ray diffraction Scherrer method. The specific surface area (BET) was 8.1 m ² / g. The loss on ignition at 1000 ° C. for 1 hour was 14.3%. Bulk density is 0.46 g / cm ³
Met. Chlorine was measured by a turbidimetric method, and nitrogen was measured by a combustion-IR method. Chlorine was 120 ppm and nitrate ion was 70 ppm.

As can be seen by comparing Example 1 and Comparative Example 1, the physical property values of neodymium hydroxide produced by the method of the present invention and neodymium hydroxide produced by the wet method are different. The neodymium hydroxide of Example 1 had a crystallite particle size of 30 nm, and the secondary particles had an average particle size of about 0.9 μm (D ₅₀ = 0.88 μm).
m), the color difference value L ^* is 91.7, a ^* is 4.74, and b ^* is-
6.9. 100 ppm chlorine, 5 nitrate ions
It was 0 ppm. On the other hand, the secondary particles of neodymium hydroxide of the comparative example have an average particle size of about 15.3 μm (D ₅₀ =
15.3 μm), the color difference value L ^* is 87.4, a ^* is 6.6,
b ^* was -10.4. Chlorine was 1000 ppm and nitrate ion was 100 ppm. It is considered that this difference in physical properties affects the difference in reactivity between the rare earth hydroxide and barium carbonate or titanium oxide. This affects the relative dielectric constant ε of the electronic ceramic and the temperature coefficient τ of the dielectric constant.

Since the temperature coefficient τ of the dielectric constant is as small as −10 ppm / ° C., the operating temperature of mobile phones and home electric appliances is −2.
The dielectric constant at about 0 to 80 ° C. is stable.
The rare earth hydroxide of the present invention is suitable as an additive for ceramic capacitors and resonators. When a trace amount of a rare earth element is added to barium titanate, a positive resistance temperature characteristic (PCT characteristic) is exhibited at a temperature near the Curie point. PCT elements utilizing PCT characteristics are used for various purposes.
In Example 2, the rare earth hydroxide of the present invention was used as a PCT material. In Comparative Example 2, an oxide was used. Since the breakdown voltage is improved, the rare earth hydroxide of the present invention is suitable as an additive for a PCT device.

[0031]

According to the present invention, electronic ceramics such as dielectric filters and ceramic capacitors and Si ₃ N _4.
Rare earth hydroxide suitable as an additive for structural ceramics such as AlN, rarely absorbs moisture during storage, has little water of crystallization and adherence, and is easily dispersed in the main ceramic material. Things are obtained.

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Claims (6)

[Claims] 1. The general formula Ln (OH) ₃ (Ln is Y, L
a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Yb, and Lu are at least one rare earth element). The particle size of the crystallite as determined by X-ray diffraction is 40 nm or less, and 300 pp of chlorine.
m and a nitrate ion of 100 ppm or less. 2. The rare earth hydroxide according to claim 1, wherein the ignition loss at 1000 ° C. for one hour is within ± 2% of the theoretical value%. 3. The rare earth hydroxide according to claim 1, wherein the secondary particles obtained by agglomeration of the crystallites have an average particle size of 0.1 μm or more and 2 μm or less. . Ln of 4. Ln (OH) ₃ is Nd, the color difference value ^{L * a * b *, L} * is 90 or more 95 or less, a ^* is 3 to 6, b ^* is -10 or more - The rare earth hydroxide according to any one of claims 1 to 3, wherein the number is 5 or less. 5. A rare earth oxide and 1.5 mol or more and 3 mol or less of water or water vapor per 30 mol of the rare earth oxide.
The method for producing a rare-earth hydroxide according to any one of claims 1 to 4, wherein the mixing is performed at a temperature of from 200C to 200C. 6. A sintered body characterized by using the rare earth hydroxide according to claim 1 as an additive.