JPS6183628A - Production of fine poder of oxides of metal containing nb - Google Patents

Abstract

PURPOSE:A Nb solution acidified with oxalic acid is allowed to react with Mg and/or Mn and the resultant solution is thermally decomposed to give the titled fine particles of uniform size which has high purity, good dispersibility, uniform composition and reactivity. CONSTITUTION:A precipitate of niobium pentahydroxide and a powder of oxalic acid are mixed and dissolved in water and the resultant solution is allowed to react with Mg and/or Mn of 0.1-1mm particle sizes. Then, the reaction mixture is made into fine drops by spraying or atomizing and subjected to thermal decomposition in a short time in a reactor such as an electric furnace at 600-1,300 deg.C, further roasted, if the thermal decomposition is incomplete, to give the title fine powder.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing Nb-containing metal oxide fine powder, more specifically, a method for producing Nb-containing metal oxide fine powder obtained by reacting an acidic solution of Nb with oxalic acid and Mg and/or Mn. The present invention relates to a method for producing Nb-containing metal oxide fine powder with high purity and uniform composition by thermally decomposing a solution.

(Prior art and its problems) Nb-containing metal oxide powder, for example (Mgl/3Nb'/
3)02 powder, (Mn 731Jb ”/3)02 powder, etc. are important as raw materials for producing electroceramics such as piezoelectric materials, pyroelectric materials, and ferroelectric materials.To explain further, these are piezoelectric materials. , PbT 03 series, PbZr, which are well known as ferroelectric materials etc.
Pb(Mg1/
3Nb2/3)o3, Pb(Mn1/3Nb2/3)
It is used as an IJK material such as 03.

At this time, the Nb-containing metal oxide powder is required to have high purity, small particle size, and uniformity and excellent dispersibility, compositional uniformity, and reactivity.

Conventionally, Nb-containing metal acids (N
There is a so-called solid-phase method in which compound powders such as oxides, carbonates, etc. of Mg, Mu, etc. are weighed, calcined, and then solid-phase reaction by crushing and calcining is repeated many times. With this method, it was difficult to produce highly pure powder due to impurities mixed in during pulverization. In addition, pulverization increases efficiency (the particle size of powder that can be produced is limited to a few squares, and the particle size tends to be non-uniform, resulting in poor reactivity; furthermore, the solid phase method produces powder with a highly uniform composition). As a method to improve the disadvantages of these solid-phase methods, a coprecipitation method is known in which a powder is produced using a solution starting material.In this method, a nitric acid solution, a hydrochloric acid solution, or a sulfuric acid solution is used as a starting solution. When inorganic acids such as solutions are used, inorganic anion impurities such as nitrates, chlorides, and sulfates that remain in the resulting powder pose a problem.To remove these inorganic anion impurities, precipitation is performed from the starting solution. After production, it is common to undergo a filtration and washing process, but it is particularly difficult to completely precipitate Mg, which has the disadvantage that it is eluted during the filtration and washing process, making it impossible to obtain the desired composition.

In addition, in the coprecipitation method, the properties of the precipitates produced are different, such as Nb being a hydroxide and Mg being an oxalate, so that the precipitates inevitably separate, resulting in poor composition uniformity. Therefore, spray pyrolysis of an organic acid solution such as oxalic acid can be considered as a method that does not introduce inorganic anion impurities during the filtration and cleaning process, but IA
Since the oxalic acid acidic solution of g can only be prepared at a low concentration, it is very expensive and cannot be used industrially. In addition, since only a low-concentration stock solution can be prepared, the thermal decomposition efficiency is low and energy costs are high, making it impractical.

In addition, in the case of Fb(Mg1/3Nb2/z)03 solid solution, PbO.

Pb(Mg
1/5Nb2/z)03 When making a solid solution, 3Pb
O-2Nb205 or 2F'bO-Nb2057', C
(7) The solid solution is a by-product 1, -CL, Pb (Mgl
/, Nb2/3) o33 It was very difficult to form a solid solution.

[National Technical Shi? - Volume 23, No. 1 (
1977), pp. 95-102 “Na5ion&lT
electrical report J Vow 23
/161 (1977) 95-102]] This is due to the reactivity of MgO and Nb206 powder, and the reactivity of Mg and N'
It is thought that the uniformity of the composition of b is also related, and Pl
)(Mg1/5Nb2/s)03 It is one of the objects of the present invention to provide a Nb-containing oxide powder that does not form a solid solution or the like.

(Means for Solving the Problems) The present inventors have found that it is possible to produce Nt+-containing fine powder with a uniform particle size and a stable oxalic acid mixture at a high concentration. Heading This invention has been achieved. That is, the present invention is a method for producing N'b-containing fine powder, which is characterized by thermally decomposing a solution obtained by reacting an acidic solution of Nb with oxalic acid and Mg and/or Mn.

The present invention will be explained in more detail below.

The method for preparing the Nb oxalic acid solution used in the present invention is not particularly limited, but the method of preparing the Nb oxalic acid solution is the method of preparing the hydrate of each mallet metal and the oxalic acid powder as previously proposed by the present applicant. Examples include the method disclosed in Japanese Patent Application No. 156293/1983 in which mixed condensate is added. Regarding the form of the metal Mg and/or Mn, the more reactive it is in powder form, the reaction is completed in a short time, but the heat generation and generation of hydrogen gas associated with the reaction are intense, so the particle size is 0.1~ 1 friendliness level is preferable.

Further, as a method for reacting Mg and/or Mn with an oxalic acid solution of Nb, a general method of mixing while stirring may be used, and the reaction temperature is not particularly limited.

Please note that gas is generated during the reaction, so care must be taken. Examples of thermal decomposition methods include spraying a solution into fine droplets, introducing the droplets into a reactor heated with an electric furnace, or into a flame of flammable gas for heat exchange. , a method of pyrolysis in as short a time as possible is preferred.

Furthermore, if thermal decomposition is incomplete in these methods, the obtained powder is further calcined. In the case of thermal decomposition in a heated reactor, the reactor temperature is preferably 600 to 1300°C. At temperatures below 6008C, heat exchange is incomplete and production efficiency is low. Furthermore, if the temperature exceeds 300°C, the equipment becomes expensive and impractical. In the case of thermal decomposition using a flame such as a flammable gas, the droplets are rapidly heated and cooled, so it is easy to obtain a fine powder, which is preferable.

Further, the calcination temperature for calcination to be carried out when thermal decomposition is incomplete is preferably 600 to 1000°C.

At a temperature of 600°C, the efficiency of thermal decomposition is low;
If the temperature exceeds °C, the powders tend to sinter and form hard aggregates (this is not preferable as it reduces the properties of the powder.Also, it is more efficient to shorten the calcination time to prevent the formation of aggregates due to sintering. be.

Examples will be further described below.

〔Example〕

Example 1 a) Production of niobium in oxalic acid solution A niobium hydroxide precipitate produced by adding ammonia water to a niobium in hydrofluoric acid solution was thoroughly washed to give a fluorine concentration of 500 pp.
m or less. An acidic solution of niobium in oxalic acid was prepared using the obtained niobium hydroxide precipitate. As a result of analyzing this solution, the niobium metal concentration Q was 465 mol/l, and the citric acid concentration was 1.228 mol/1. The analytical methods used were inductively coupled plasma analysis and redox titration, respectively.

b) Production of niobium-containing metal oxide Add metallic Mg powder to an acidic solution of niobium in oxalic acid with stirring so that the atomic ratio of Mg:Nb is 1:2,
The obtained solution was sprayed into a vertical electric furnace maintained at a temperature of 1000°C, and the resulting powder was further heated to a temperature of 900°C.
A fine powder of (Mg''/3Nb2/3)02 was obtained by calcination for 30 minutes.This powder was examined under an electron microscope (31!iM).
A photograph is shown in Figure 1. This powder had a particle size of 0.1 μm N degrees, was uniform in particle size, and had good dispersibility. Further, powder X-ray diffraction revealed that it was MgNb2O, a single phase. As a result of emission analysis and carbon analysis, impurities were found to be highly pure with almost no impurities being contained at a few ppm or less.

In addition, in order to evaluate the reactivity and compositional uniformity of this powder, Pb (Mgl/5Nb2/,)O! 3 composition): - Pb (M
g1/3Nb''/3)o3 single phase ivy. Its powder X-ray diffraction pattern is shown in Figure 2.

Example 2 Example 1 so that the atomic ratio of Mn:Nb was 1=2.
Example 1 was carried out in the same manner as in Example 1, except that metallic Mn powder was added to the oxalic acid acidic Nb solution obtained in . The results had the same characteristics as Example 1 (Mn1/2Nb2//,)
02 fine powder was obtained.

Example 3 Same as Example 1 except that metal Mg and metal Mn were added to the oxalic acid acid solution of Nb obtained in Example 1 so that the atomic ratio of Mg:Nb:Mn was 4:8:1. I did it. Are the results similar to those in Example 1? A fine powder was obtained.

〔Effect of the invention〕

According to the present invention, it is possible to efficiently and inexpensively produce Nb-containing fine powder that is highly pure, has a small and uniform particle size, and has excellent dispersibility, compositional uniformity, and reactivity.

[Brief explanation of drawings]

FIGS. 1 and 2 are an SKM photograph and an X-ray diffraction diagram showing the particle structure of the powder obtained in Example 1, respectively. Patent applicant Denki Kagaku Kogyo Co., Ltd. 14-2-P-Pengzhou

Claims (1)

[Claims] Nb characterized by thermally decomposing a solution obtained by reacting an oxalic acid acidic solution of Nb with Mg and/or Mn
Method for producing fine metal oxide powder.