JPS6071528A - Manufacture of m-phase type hexagonal ferrite particle - Google Patents

Abstract

PURPOSE:To obtain the titled uniform and fine particles without carrying out mechanical mixing or grainding by adding the chloride of a specified bivalent metal to an aqueous mixture of Na carbonate with fine Fe oxide to precipitate the carbonate of the bivalent metal, carrying out uniform mixing, separating the solid phase, and calcining it after washing and drying. CONSTITUTION:To an aqueous soln. of Na2CO3 is added Fe oxide or hydroxide such as needlelike gamma-Fe2O3, and they are mixed. An aqueous soln. of the chloride of R<2+> (R is one or more among Ba, Sr, Pb and Ca) such as BaCl2.2H2O is added to the aqueous mixture to precipitate BaCO3. This BaCO3 is uniformly mixed with the gamma-Fe2O3 in the aqueous mixture by stirring the mixture. The solid phase is separated, washed, dried, and calcined at 800-1,400 deg.C in the air. The resulting M-phase type hexagonal ferrite particles have a small particle size such as about 0.1-0.3mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to oxide magnetic particles and a method for producing the same, and its purpose is to produce 1% to 2M star-type hexagonal ferrite particles.

M-phase hexagonal ferrite (hereinafter simply referred to as M-phase ferrite) is currently used in other magnets as an anisotropic magnet with low cost and high performance, as represented by Ba and Sr-based permanent magnet materials. It is as good as anything.

On the other hand, in recent years, a perpendicular magnetic recording system has been proposed as a high-density magnetic recording method, and a 2M phase star hexagonal ferrite element is required as a material for magnetic tapes and disks as its magnetic medium.

Apply it to the pace tape while magnetically aligning it.

Uniaxial anisotropy perpendicular to the tape surface can be achieved
, at least one of Sr, Pb and Ca) and α-Fe205? - It is obtained by mechanically mixing in a Lemile or Raikai machine and firing in the atmosphere at a temperature of 1100°C or higher. In addition, after that, mechanical crushing is carried out in a mill or a vibration mill, and 0.5 to 2. The usual method is to form particles of about Ottm.

However, in the conventional mechanical mixing method mentioned above.

R carbonate and α-Fe20. There was a drawback that a uniform M phase was not obtained during the course of the two reactions due to insufficient mixing between the two, and subsequent mechanical crushing was unable to obtain uniform, fine particles with a narrow particle size distribution.

In view of these points, it is an object of the present invention to provide a manufacturing method for obtaining uniform and fine M-phase ferrite particles without mechanical mixing or mechanical pulverization.

In the method of the present invention, Na carbonate and very fine Fe oxide or hydroxide are mixed in water as starting materials, and R2+ (where R is Ba, S
Adding a chloride of R, Pb and at least one of Ca) to precipitate a carbonate of R2+, stirring the aqueous solution,
R2+ carbonate and Fe oxide or hydroxide are mixed uniformly, and then the solid phase is separated and washed.

This is a method for producing M-phase hexagonal ferrite particles characterized by drying and firing to obtain 2M-phase ferrite particles.

Here, the size of M phase ferrite particles after firing is set to 0.
．． To make the particles as fine as 1 to 0.3 μm and to narrow the particle size distribution, use a low temperature (around 900°C).

It is desirable to perform firing without sintering, and in practical terms, firing is performed at a temperature of 800°C to 1400°C, ranging from several minutes to several centimeters.
It is sufficient to select within the range of 0 hours.

Hereinafter, one embodiment of the present invention will be described in detail.

Example-1 0.0 of sodium carbonate Na2CO3 as starting material
Dissolve 75 mol in 450 cc of water and use this as solution A.

Acicular iron oxide r-Fe2o3 (long axis 0.281
1m.

0.30 mol and 0.27 mol, respectively (minor axis 0.03 μm)
It was weighed and added under four conditions: 5 mol, 0.25 mol, o', and 225 mol. Also, barium chloride BaCt2・2H20
0.05 mol of (dihydrate) was dissolved in 200 cc of water to prepare B solution. Add solution B (50°C) dropwise to solution A at room temperature.

Precipitate barium carbonate B a CO5, r-Fe20
5 and baked while stirring. The saturation magnetization moment σ8 and coercive force XHc per unit weight of the fired ferrite particles were measured using a sequential vibrating magnetometer. Furthermore, the grain size and distribution state were observed using a scanning electron microscope, and phase changes were investigated using X-ray diffraction. The results are shown in Table 1.

As is clear from Table 1, the saturation magnetization σB per unit weight increases as the firing temperature increases, and the maximum value was 60.7 emu/at 1100°C for 3 hours at 0.25 mol.
gr was obtained. Furthermore, as the temperature increases, the coercive force I'Hc decreases because grain growth occurs and the grain size increases. The particle size is 90 when r-Fe203 is 0.25 mol.
Since sintering does not occur near 0°C and 1000°C, single grain growth does not become coarse (0.1 to 0.3 μm, fine particles with a narrow distribution width were obtained. According to X-ray diffraction At 900°C, unreacted Fe2O3 still remained, but at 1000°C it almost disappeared, and at 1100°C it was a complete square plate-shaped M phase.

Under conditions of 1000° C. for 3 hours, ideal particles of fine and uniform M phase single phase of 0.2 to 0.3 μm were obtained.

Example-2 0.05 of sodium carbonate Na2CO3 as starting material
Dissolve 5 moles in 450 cc of water and use this as Solution A.

Acicular goethite α-FeOOH (long axis 0.5
0μm.

0.60 mole (minor axis 0.07 μm), 0.55 mo/I
/, 0.50 mol, and 0.45 mol were weighed and added under four conditions. Also, barium chloride BaC62・2H20 (dihydrate)
0.05 mol of the solution was dissolved in 200 cc of water to prepare solution B. Solution B (50°C) was added dropwise to solution A at room temperature to precipitate Norium carbonate naco5, and this aqueous solution was stirred to thoroughly mix BaCO3 and α-FeOOH. After that, solid-liquid separation, water washing, and drying are performed at 900℃~
It was baked in the air for 3 hours at a temperature of 1,100 mm. The thus obtained powder was subjected to magnetic measurement, scanning electron microscopy, and X-ray diffraction in the same manner as in Example-1. The results are shown in Table 2.

As is clear from Table 2, σS increases as the calcination temperature increases, reaching a maximum value of 63.0 at 9.50 mol and 3 hours at 1100°C. Oemu/gr was obtained at 90. On the other hand, the particle size increased with increasing temperature.

M-phase particles were obtained, and particles with a relatively small particle size and narrow particle size distribution were obtained near 900°C and 1000°C.

According to X-ray diffraction, only a small amount of unreacted Fe was found at 900°C.
If the temperature is higher than 2O3, it will be completely 4M.
It was phase.

0.2-0.3μ under the condition of 900℃ for 3 hours.
M-phase fine particles with a fineness of about 100 m and high uniformity were obtained.

2 As is clear from the above examples, according to the method of the present invention, 12+ chloride is chemically reacted with Na carbonate to precipitate R2+ carbonate, and very fine Fe oxide or By mixing with hydroxide, uniform fine M-phase hexagonal ferrite particles can be obtained.

Therefore, when comparing the ferrite particles obtained by the method of the present invention with the ferrite particles obtained by conventional mechanical crushing using an anisotropic magnet, it is found that the pressability is not good because the particles are uniform, the density, and the magnetic properties ( Br, 'tic) were both improved by more than 5 inches.

Claims (1)

[Claims] 1. As a starting material, Na carbonate and very fine Fe oxide or hydroxide are mixed in water, and R2+ (where R is Ba, Sr. pb) is added to the solution. and at least one type of Ca) and R
2+ carbonate is precipitated, the aqueous solution is stirred to uniformly mix R8+ carbonate and Fe oxide or hydroxide, and then the solid phase is separated, washed, and dried. A method for producing nine M-phase hexagonal ferrite particles, characterized by obtaining fine and uniform M-phase ferrite particles by firing.