JP3265368B2 - Method for producing zirconium oxide powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to stabilized or partially stabilized zirconium oxide powder. The stabilized or partially stabilized zirconium oxide powder is used for producing a structural material or the like made of a stabilized or partially stabilized zirconia sintered body by molding and calcining. In the present specification, “hydrated zirconia” refers to what is called zirconium hydroxide, crystalline hydrated zirconia, amorphous hydrated zirconia, or the like.

[0002] In this specification, the term "solid solution reaction" refers to a reaction in which a hydrated zirconia powder containing a stabilizer is converted into a stabilized or partially stabilized zirconia oxide powder by heating.

[0003]

2. Description of the Related Art Hitherto, a stabilized or partially stabilized zirconium oxide powder has been produced by calcining a hydrated zirconia powder containing a stabilizer such as yttria, magnesia or calcia. The calcination is performed by heating the hydrated zirconia powder containing the stabilizer to a temperature at which the hydrated zirconia powder changes to a stabilized or partially stabilized zirconia oxide powder, that is, a temperature equal to or higher than the solid solution reaction temperature. . In this case, the heating rate in the calcination step often depends mainly on the productivity and the performance of the calcination furnace.

[0004]

However, the prior art still has problems. In other words, the powder obtained after calcination has a low stabilization rate or a high calcination temperature in order to obtain a high stabilization rate. An object of the present invention is to provide a method for producing a stabilized or partially stabilized zirconium oxide powder, which solves the above problem.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that when hydrated zirconia powder containing a stabilizer is calcined to produce a stabilized or partially stabilized zirconia oxide powder, the hydrated zirconia powder is produced. In the calcination step, a method for producing a zirconium oxide powder characterized in that the temperature is raised at a rate of 1.0 ° C. or less per minute to a temperature at which a solid solution reaction starts is solved, and the invention was completed. did. The details will be described below.

The hydrated zirconia powder containing a stabilizer in the present invention can be produced by a known method. For example, the concentration of the hydrated zirconia particle suspension may be determined by converting the hydrated zirconia particles in the hydrated zirconia particle suspension into ZrO ₂ , from about 10 to about 2000 g / liter, preferably 100 The suspension can be prepared by preparing a solution having a range of １０００1000 g / liter and drying the suspension. The concentration of the hydrated zirconia particle suspension is not unique due to drying conditions and the like. The method for producing the hydrated zirconia particle suspension is not limited to a water-soluble zirconium salt hydrolysis method, a neutralization precipitation method, and the like. Among them, preferred is a water-soluble zirconium salt hydrolysis method. And particularly preferably a hydrolysis method of an aqueous solution of zirconium oxychloride.

[0007] As stabilizers for the solid solution reaction, Y,
Preference is given to using chlorides, nitrates, sulphates, oxides and / or hydroxides, such as Ca, Ce and Mg, or suspensions of said compounds. Further, a suspension of the hydrated zirconia particles to which a chloride such as Y, Ca, Ce, and Mg, a nitrate, a sulfate, an oxide or a hydroxide, or the above compound is added. That is, it is preferable to form a stabilized or partially stabilized zirconia particle powder after calcination, but the stabilizer may be added at any time before the calcination step, and the addition method is limited. There is no.

The suspension containing the stabilizer may be dried as it is, or Y, Mg, Ca or the like in the suspension may be precipitated as a hydroxide or the like. The average primary particle diameter of the hydrated zirconia particles in the present invention is preferably from 10 to 500 nm, more preferably from 50 to 500 nm.

The hydrated zirconia particle suspension used in the present invention is preferably subjected to washing or the like to reduce impurities such as chloride ions, nitrate ions and alkali metals in advance, but according to the method of the present invention. The amount of impurities can also be reduced by washing the suspension solution after spray drying or calcination.

The hydrated zirconia particle suspension is dried.
Drying is preferably performed by spray drying. Drying methods other than spray drying, for example, in the case of static drying, the dried powder becomes a block, it is difficult to perform a uniform heat treatment by calcination, in order to be uniform, a pulverization step after drying is required, Large loss in energy. The temperature for spray drying may be a commonly used temperature, preferably drying at a temperature of 50 to 250 ° C, more preferably 100 to 200 ° C.

Before the drying, an organic compound or a surface treating agent may be added in order to control the powder properties of the dried hydrated zirconia particles. As the organic compound therefor, alcohols, esters, surfactants and the like are preferably used. Particularly, alcohols having 1 to 10 carbon atoms are preferable. The amount of the organic compound added is 0.01 to 0.01 based on the organic compound-containing Zr in the hydrated zirconia particle suspension.
The range is preferably from 10 to 10 mol%, more preferably from 0.01 to 1 mol% based on the contained Zr.

Further, if necessary to control the powder characteristics of the dried particles, the viscosity of the hydrated zirconia particle suspension is adjusted before drying. It is preferable that the viscosity is adjusted so that the viscosity of the hydrated zirconia suspension is about 50 to 5000 cP. The viscosity may be adjusted with an acid or an alkali, or a coagulant, a surfactant, an organic polymer, or the like may be added.

The hydrated zirconia powder used in the present invention preferably has a light bulk density of 1.0 to 2.0 g / cm ³ . The water content of the hydrated zirconia powder is preferably 15% or less, more preferably 10% or less. The dried hydrated zirconia particles are calcined.

The calcination may be performed by a usual method such as no pressurization in an oxygen atmosphere. The calcination temperature is preferably from 600 to 1300 ° C., and the holding time at the temperature is preferably 1 hour or more.

In the present invention, the rate of temperature rise in the calcination step is 1.0 to 1 min.
It is essential to raise the temperature at a rate of not more than ° C.

The temperature at which the solid solution reaction starts depends on the amount and type of the stabilizer, but is generally 300 to 900 ° C.

Preferably, the temperature is raised at a rate of 0.5 ° C. or less per minute. Further, it is more preferable that the temperature is raised from 300 ° C. to the temperature at which the solid solution reaction starts at a rate of 1.0 ° C. or less per minute, and it is particularly preferable that the temperature be raised at a rate of 0.5 ° C. or less. If the heating rate exceeds 1.0 ° C. per minute, the powder obtained after calcination tends to have a low stabilization rate or a high calcination temperature in order to obtain a high stabilization rate.

The solid solution reaction can be confirmed by the appearance of a tetragonal peak by observing, for example, an X-ray diffraction image, a Raman spectrum and the like of the powder.

The heating rate may be any rate after the start of the solid solution reaction. If the heating rate does not affect the properties of the powder up to the drying temperature, the temperature may be increased at an arbitrary heating rate. From the viewpoint of productivity, etc., the temperature is raised at a rate of about 5 ° C./min up to the drying temperature, and then is raised at a rate of 1.0 ° C./min or less until the temperature at which the solid solution reaction starts. After the start temperature, the temperature is preferably raised at a rate of 2.0 ° C./min or less. The generated zirconium oxide powder is washed and pulverized as necessary to obtain a zirconium oxide powder.

[0020]

The reason why the zirconium oxide powder obtained by the production method of the present invention can obtain a high stabilization rate at a high or low calcination temperature of the powder obtained after calcination is high or low. Although not always clear, it is presumed to be due to the following reasons.

When calcining a hydrated zirconia powder containing a stabilizer, the following reaction is considered. (1) Before the solid solution reaction: change in the state of the hydrated zirconia particles containing the stabilizer by heating, and (2) during the solid solution reaction: the hydrated zirconia powder containing the stabilizer is stabilized by heating or (3) During and after the solid solution reaction: a solid solution reaction changed into partially stabilized zirconium oxide powder: particle growth caused by heating of the stabilized or partially stabilized zirconium oxide powder changed by the solid solution reaction. Here, it can be assumed that the solid solution reaction of (2) is greatly affected by the state of the powder before the start of the reaction. Furthermore, the state before the solid solution reaction of (1) affects the particle growth of the stabilized or partially stabilized zirconium oxide powder of (3), and the stabilized or partially stabilized zirconium oxide powder becomes a product. It is estimated that there will be differences in characteristics and the like.

In the present invention, in the calcination step, the temperature is raised at a rate of 0.5 ° C. or less per minute to a temperature at which the solid solution reaction starts, whereby the hydration containing the stabilizer in (1) is performed. It is presumed that rapid aggregation of the zirconia particles is suppressed and the state of the hydrated zirconia particles in which the stabilizer is uniformly dispersed is obtained. Therefore, since the stabilizer is uniformly dispersed in the subsequent solid solution reaction, the solid solution reaction proceeds uniformly in each particle, and as a result, the stabilization rate is higher or lower than the conventional method. It is estimated that a high stabilization rate can be obtained by using On the other hand, in the conventional method, in (1), the hydrated zirconia particles containing the stabilizing agent rapidly agglomerate, so that the stabilizing agent is in a non-uniform state, and a low stabilizing rate or a high stabilizing rate is obtained. Therefore, it is presumed that a high calcination temperature is required.

[0023]

According to the method for producing zirconium oxide particles of the present invention, the stabilization rate of the stabilized or partially stabilized powder obtained even at the calcination temperature in the conventional method is high. Products with the same degree of stabilization can be obtained at low calcination temperatures.

[0024]

【Example】

3 _mol% in terms of Example _{1 Y 2 O 3 (Y 2} O 3 in terms of value and Zr
O ₂ in terms of value to the sum of the. The same applies to the following)
including l _3, after boiling hydrolyzing zirconium oxychloride aqueous solution of ZrO ₂ concentration in terms 50 g / liter, the Z
Concentration was performed until the concentration in terms of rO ₂ became 300 g / liter, and a suspension of hydrated zirconia particles having an average primary particle diameter of 100 nm (by a particle size distribution analyzer using a photon correlation method) and a crystallite diameter of 4 nm. A liquid was obtained.

The solution was spray-dried with a spray drier. The obtained dried particles were spherical and had a light bulk density of 1.25 g / cm ³ . After heating the dried powder at various temperatures, the result of measuring Raman spectrum,
A tetragonal peak was observed at 500 ° C.

The dried powder was calcined. In the calcination, the temperature is raised at a rate of 0.5 ° C./min up to 500 ° C., and then at a rate of 2.0 ° C./min up to 600 ° C., and the temperature is maintained at 600 ° C. for 2 hours. Obtained. The stabilization rate (%) was calculated from the formula shown by Garvie and Nicholson as follows. (. Hereinafter, the same) stabilized rate (%) = It / (It + Im1 + Im2) × 100 (%) It: integrated intensity of tetragonal in X-ray diffraction (111) Im1: Monoclinic in the X-ray diffraction of the (111) Integrated intensity Im2: Integrated intensity of monoclinic (11 -1 ) in X-ray diffraction The stabilization rate (%) of the obtained powder was 82%.

Even when the obtained powder was pulverized to an average particle diameter of about 1 μm, the decrease in the stabilization ratio was small.

Example 2 The calcination conditions were such that the temperature was raised at a rate of 0.5 ° C./min up to 500 ° C., and then at a rate of 2.0 ° C./min up to 700 ° C.
The procedure was performed under the same conditions as in Example 1 except that the temperature was kept at 00 ° C. for 2 hours. The obtained powder had a stabilization ratio (%) of 88%. Even if the obtained powder was pulverized to an average particle size of about 1 μm, the stabilization ratio was only slightly reduced.

Example 3 The same procedure as in Example 1 was carried out except that the calcination condition was raised to 700 ° C. at a rate of 0.5 ° C./min and maintained at 700 ° C. for 2 hours. The stabilization rate (%) of the obtained powder was 92%. Even if the obtained powder was pulverized to an average particle diameter of about 1 μm, the stabilization ratio was only slightly lowered.

Example 4 Including YCl ₃ in an amount of ₃ mol% in terms of Y ₂ O ₃ ,
An aqueous solution of zirconium oxychloride having a concentration of 50 g / liter in terms of ZrO ₂ was hydrolyzed by boiling and then neutralized with an aqueous alkali solution. The obtained hydrated zirconia suspension was dried to obtain a hydrated zirconia powder. After heating the dried powder at various temperatures, the Raman spectrum was measured.
As a result, a tetragonal peak was confirmed.

The dried powder was calcined. In the calcination, the temperature is raised at a rate of 0.5 ° C./min up to 400 ° C., and then at a rate of 2.0 ° C./min. Obtained. The stabilization rate (%) of the obtained powder was 90%. Even if the obtained powder was pulverized to an average particle diameter of about 1 μm, the stabilization ratio was only slightly lowered.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the calcination conditions were raised to 600 ° C. at a rate of 5.0 ° C./min and maintained at 600 ° C. for 2 hours. The stabilization rate (%) was 74%. When the obtained powder was pulverized to an average particle diameter of about 1 μm, the stabilization rate was greatly reduced.

Comparative Example 2 The same conditions as in Example 1 were used except that the calcination conditions were increased to 700 ° C. at a rate of 5.0 ° C./min and maintained at 700 ° C. for 2 hours. The stabilization rate (%) was 83%. When the obtained powder was pulverized to an average particle diameter of about 1 μm, the stabilization rate was greatly reduced.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C01G 25/02 CA (STN)

Claims (1)

(57) [Claims] 1. A hydrated zirconia powder containing a stabilizer is calcined to produce a stabilized or partially stabilized zirconium oxide powder. A method for producing zirconium oxide powder, wherein the temperature is raised at a rate of 1.0 ° C. or less.