JPH07315835A - Acicular particle of oxide of rare-earth element and its production - Google Patents

Abstract

PURPOSE:To provide acicular particles of a rare-earth metal oxide and useful for a ceramics source, etc. CONSTITUTION:This oxide of a rare-earth element comprises acicular particles having a length of 1-10mum. a diameter of <=1mum and a (length/diameter) ratio of >=10. This method for producing the acicular particles of the rare-earth element is to add urea to a salt solution of the rare-earth element, heat the resulting mixture in an autoclave at >=100 deg.C for >=1 hours and separate and dry the precipitate and bake the product.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a raw material of a rare earth element oxide sintered body used for a metal melting crucible having a high melting point and a high activity, a rare earth element oxide acicular particle suitable for a ceramic material, and the like. The present invention relates to a manufacturing method thereof.

[0002]

2. Description of the Related Art When urea is added to an aqueous solution of a salt of a rare earth element and heated, the rare earth element is precipitated as a mixture of a carbonate and a hydroxide by a carbonate ion and a hydroxide ion produced by hydrolysis of urea. It is known as the urea method.

[0003]

When the hydrolysis of urea in the above method is carried out in an open system, that is, at a temperature below the boiling point of water, the resulting precipitate and the oxide obtained by calcination thereof have a particle shape. Are spherical and the average particle size is often 0.5
μm or less. The spherical shape is not always ideal depending on the use of the rare earth element oxide particles, and when forming a sintered body containing a rare earth element oxide as a main component, the needle shape is more suitable because the molding density is easily increased. Also, when the hydrolysis of urea is carried out at a temperature below the boiling point of water, even if the amount of urea is increased to about 50 mol or more per 1 mol of rare earth element, the reaction does not proceed completely and the yield It also has the drawback of not being very good. The present invention solves such a drawback, and is intended to produce a rare earth element oxide composed of acicular particles by a urea method with a high yield.

[0004]

Means for Solving the Problems In order to solve the above problems, the present inventors have studied that precipitation of rare earth elements by the urea method is performed in a pressure vessel (autoclave) at a temperature of 100 ° C. or higher. The present invention has been completed by establishing various conditions and finding that a precipitate composed of acicular particles can be obtained in good yield. The gist thereof is 1 to 10 μm in length and 1 μm in thickness.
The following and (length / thickness) = needle-like particles of rare earth element oxide consisting of 10 or more needle-like particles, and urea is added to an aqueous solution of a salt of a rare earth element, and the temperature is 100 ° C or more in an autoclave for 1 hour or more. It is a method for producing acicular particles of a rare earth element oxide, in which a precipitate obtained by heating is separated, dried and then calcined.

The present invention will be described in detail below. To a 0.01 to 0.5 mol / L aqueous solution of a salt of a rare earth element, add 2 to 20 moles of urea per mole of the rare earth element, and add 100 to 100 in an autoclave.
Heat at ℃ or more for 1 hour or more. Rare earth elements with a length of 1-10 μm, a thickness of 1 μm or less and a length / thickness ratio of 10 or more can be obtained by filtering the formed precipitate, washing it with water, and then baking it at 700 to 900 ° C. for about 1 hour. The oxide acicular particles are obtained almost quantitatively. As the salt of the rare earth element, chloride, nitrate, acetate or the like is used. If the heating temperature is less than 100 ° C or the heating time is less than 1 hour, the reaction is insufficient and the yield is poor. The upper limit of temperature is determined by the pressure resistance of the autoclave used, but is usually around 170 ° C. When the composition analysis and X-ray diffraction pattern of the obtained precipitate are measured, the precipitate is identified as y ₂ (CO ₃ ) ₃ .2H ₂ O in the case of yttrium. On the other hand, when urea is hydrolyzed in an open system at a temperature below the boiling point of water, the precipitate obtained is Y (CO ₃ ).
It is represented by OH, and differs greatly in this respect. The applicable range of the present invention is Y, La, Ce, Pr, as rare earth elements,
Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu
One element selected from the above, or a mixture of two or more elements.

[0006]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Example 1) 0.25 mol / L yttrium nitrate aqueous solution 700
52.5 g of urea was added to ml to dissolve completely. Put this solution in an autoclave equipped with a stirring blade, and use a motor to
The mixture was heated to 120 ° C with a heater while stirring at 500 rpm.
At this time, the pressure became 0.31 MPa. It was kept at 120 ° C for 2 hours. After cooling, the mixture was filtered with a Buchner funnel and sprinkled twice with 500 ml of pure water for washing. The obtained precipitate was air-dried and then calcined in the air at 800 ° C. for 1 hour to obtain 19.67 g of yttrium oxide (yield 99.6%). The center particle size of this oxide as measured by the laser diffraction scattering method was 2.60 μm. Also, when observed with an electron microscope, the length is 2 to 4 μm and the thickness is 0.
It consisted of acicular particles of 1 to 0.2 μm.

Example 2 Example 1 was repeated except that a gadolinium nitrate aqueous solution was used instead of yttrium nitrate.
And treated in the same manner as above to obtain 31.57 g of gadolinium oxide in a yield of 99.5.
Earned in%. The center particle size of this oxide as measured by the laser diffraction scattering method was 2.75 μm. Further, when observed with an electron microscope, it consisted of needle-shaped particles having a length of 2 to 4 μm and a thickness of 0.1 to 0.2 μm.

(Comparative Example) To 700 ml of a 0.05 mol / L yttrium nitrate aqueous solution, 52.5 g of urea was added and completely dissolved. This solution was put into a three-necked round bottom flask equipped with a reflux condenser and a stirring blade, and heated to 98 ° C. with a mantle heater while stirring with a motor at about 500 rpm. It was kept as it was at 97 to 99 ° C for 2 hours. After cooling, the mixture was filtered with a Buchner funnel and sprinkled with 200 ml of pure water twice for washing. The obtained precipitate was air dried and then calcined in the air at 800 ° C. for 1 hour to obtain 3.66 g of yttrium oxide (yield 92.6%). The center particle size of this oxide as measured by the laser diffraction scattering method was 0.61 μm. Also, when observed with an electron microscope, it consisted of spherical particles.

[0009]

Industrial Applicability According to the present invention, needle-like particles of rare earth element oxide useful as a ceramic raw material and the like can be obtained in high yield, and its utility value is industrially extremely high.

Claims (2)

[Claims] 1. Rare earth element oxide acicular particles consisting of acicular particles having a length of 1 to 10 μm, a thickness of 1 μm or less and (length / thickness) = 10 or more. 2. The rare earth element oxidation according to claim 1, wherein urea is added to an aqueous solution of a salt of a rare earth element and the precipitate obtained by heating in an autoclave at a temperature of 100 ° C. or higher for 1 hour or more is separated, dried and calcined. A method for producing needle-shaped particles.