JPH04211102A - Production of hexagonal ba ferrite fine particle powder for magnetic recording - Google Patents

Abstract

PURPOSE:To provide a method for industrially producing hexagonal Ba ferrite fine particle powder having appropriate antimagnetic force, high magnetization value and excellent in orientation and dispersive power. CONSTITUTION:Hexagonal Ba ferrite fine particles are created from an aqueous solution and treated in an aqueous solution containing Si(IV) and then subjected to heat treatment at a temperature lower than 900 deg.C thus preventing sintering of the hexagonal Ba ferrite fine particle and interparticle sintering.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to Fe (
III) with a coercive force reducer, for example, Ti(IV)
and Co (I I) or Ti (IV) and Mn, Zn
Divalent metal ions other than Co(II) such as M (II)
The present invention relates to a method for producing a hexagonal plate-shaped Ba ferrite fine particle powder substituted with [0002]

[Prior Art] In recent years, ferromagnetic non-acicular particles having appropriate coercive force (Hc) and large magnetization (M) values and excellent orientation and dispersibility have been used as magnetic materials for recording, especially It is becoming desired as a magnetic material for perpendicular magnetic recording. [0003] Conventionally, one method for producing Ba ferrite has been a method in which an alkaline suspension containing Ba ions and Fe (II I) is subjected to hydrothermal treatment using an autoclave as a reaction device (hereinafter referred to as this). (simply referred to as hydrothermal treatment) is known, and according to this hydrothermal treatment method, Ba ferrite particles are precipitated by selecting reaction conditions. These precipitated particles usually have a hexagonal plate shape, and since they are generated from an aqueous solution, the particles are separated one by one, so they have excellent dispersibility during paint production. [0004] Due to the production method called hydrothermal treatment, ferric salts such as ferric chloride and Ba such as barium chloride
The so-called coprecipitation method involves mixing a salt and an alkaline aqueous solution to form a coprecipitate, followed by heating and firing, using an iron raw material such as ferric oxide, a Ba raw material such as barium carbonate, and a vitrified substance such as H3BO2. Compared to the so-called glass crystallization method, etc., in which a mixture of ) (hereinafter referred to as plate ratio) is large, especially 1
It also has the characteristic that particles of 0 or more can be easily obtained. [0005]

[Problems to be Solved by the Invention] There is currently a demand for plate-shaped Ba ferrite fine particle powder that has appropriate coercive force and large magnetization value, and has excellent orientation and dispersibility. A plate-shaped Ba ferrite fine particle powder that fully satisfies these characteristics has not yet been obtained by the hydrothermal treatment method as described above. (0006), i.e. coercive force reducing agents, such as Ti(IV
) and Co (I I), if necessary Co (I I
) Ba ferrite produced from an aqueous solution by hydrothermal treatment in the presence of divalent metal ions such as Fe, Zn, Mn, etc., such as BaFe+2-2M Ti 0+
9 The hexagonal plate-like particles with the composition (0,6≦X≦1.2) are particles that are separated one by one and have a plate-like ratio of 10 or more, but as M (I I) When Co ions are added, the Hc value decreases as the X value increases, and decreases to about 1000e at an X value of 1.2. [0007] Furthermore, when the X value is 0.3 or more, the magnetization value at 10 KOe is small, and only about 40 emu g-1 can be obtained at most. M (I I) as Co (
When part of II) is changed to Fe, Zn, or Mn, the magnetism changes slightly depending on the type of metal ion and the amount of change. [0008] Conventionally, in order to improve the magnetization value of plate-shaped Ba ferrite particles, a method has been known in which plate-shaped Ba ferrite particles generated from an aqueous solution are heated at a temperature of 800° C. or higher (Japanese Patent Application Laid-Open No. 1983-1999) 160328). However, when using this method, sintering occurs between the particles and each other due to heating and firing, so the particles are separated one by one, making it impossible to obtain plate-shaped Ba ferrite fine particles with a large plate-like ratio. do not have. [0009] Therefore, the technical problem of the present invention is to obtain plate-like Ba ferrite fine particles having a suitable coercive force and a large magnetization value, each particle being disjoint, and having a high plate-like ratio. shall be. [00101

[Means for Solving the Problems] The above technical problems can be achieved by the present invention as follows. [0011] That is, the present invention provides hexagonal plate-shaped B from an aqueous solution.
5i (IV
This is a method for producing a hexagonal plate-shaped Ba ferrite fine particle powder for magnetic recording, which is characterized in that it is treated with an aqueous solution containing (1) and then heat-treated at a temperature of 900° C. or less. [00121 Next, various conditions for implementing the present invention will be described. [0013] As the particles to be treated in the present invention, plate-shaped Ba ferrite fine particle powder produced from an aqueous solution by a hydrothermal treatment method can be used, and if necessary, Fe(
A part of I I
i(IV) and Co(II), or Ti(IV)
and particles substituted with divalent metal ions M(II) other than Co(II) such as Mn and Zn, for example, BaFe+2
Particles having a composition of -2 MTi019 (0,6≦X≦1.2) can be used. [0014] As the aqueous solution containing 5i(IV) in the present invention, well-known water glass, colloidal silica, potassium silicate, etc. can be used. [0015] The amount of Si (IV) is 0.1 to 2.5% by weight in terms of Si with respect to the plate-shaped Ba ferrite fine particles. If it is less than 0.1% by weight, the effect of preventing sintering between particles and between particles will not be sufficient. 2.5% by weight
Although the effect of preventing sintering between particles and between particles can be obtained even when the value exceeds 50%, the magnetization value of the obtained hexagonal plate-shaped Ba ferrite particles decreases due to an increase in 5t (IV), which does not affect magnetism. [0016tThe heating temperature in the present invention is 900°C or lower. If the temperature exceeds 900°C, sintering of particles and particles occurs, and the BET specific surface area becomes less than 30 m2g-1. The lower limit of heating temperature is 600℃, preferably 7
00℃ or higher. [0017] [Operation] First, the most important point in the present invention is to generate hexagonal plate-shaped Ba ferrite fine particles from an aqueous solution, treat the fine particles with an aqueous solution containing 5t(IV), and then heat the particles at 900°C.
It is a fact that when heat-treated at the following temperature, plate-shaped Ba ferrite fine particles having appropriate coercive force and large magnetization value and excellent orientation and dispersibility can be obtained. [0018tIn the present invention, for example, the plate-like particles have a diameter of 0.1 to 0.4 μm, a plate-like ratio of 10 to 44, and B
The ET specific surface area (S) value is 30 to 50 m''g-', and the magnetization (M) value under a magnetic field of 10 KOe is 40 em
ug' or more and the coercive force (Hc) value is 500 to 100
0 0e hexagonal plate-shaped BaFe+2-2M Ti
019 (0゜6≦X≦1.2, M is Co (I I
) or Co (I I) and a divalent metal ion other than Co. ) can be obtained. [0019] A representative part of the numerous experimental examples conducted by the present inventor will now be extracted and explained as follows. [00201 Figures 1 and 2 show two representative samples, BaFe+o, 5COo6Tio, s019 and BaFe9.8 CO+, +Ti+, +019, which were heated for 2 hours in the air at each temperature from 300 to 900°C. The (M) value and Hc value for each case are plotted against each treatment temperature. (In the diagram 00211, ○ mark is BaFe+o, 5COo6T
iO,6019, * mark is BaFe9. s Co+, +
This is a case where Ti+, +019 is used. These samples were treated with an aqueous solution containing 4% by weight of 5t(IV) and then subjected to the same heat treatment. Magnetism at each heat treatment temperature is 5i (IV) although there is no significant difference from the above.
It has been found that the progress of sintering at high temperatures (above 700° C.) is significantly hindered by the presence of . [00221 Figure 3 shows BaFe+o, 5CO as a representative example.
5i(I) when using o7sT i O,75019
This figure shows the processing temperature dependence of the S value depending on the presence or absence of V). In the figure, the ◯ marks are for the case without Si treatment, and the * marks are for the case with St treatment. According to electron microscopy, there is little change in the particle shape and size of the heat-treated product at 700° C. or lower before and after the heat treatment, regardless of the presence or absence of 5t (IV). Processing temperature is 700
℃ or higher, S becomes small due to sintering between particles in the absence of 5i(IV). [0023t Figures 4 and 5 are electron micrographs (X100000) of Ba ferrite particles obtained by heat treatment at 800°C, and Figure 4 is 5i (IV)
In the case of no treatment, FIG. 5 shows the case of 5t(IV) treatment. [0024t Figures 6 and 7 are electron micrographs (X100OOO) of Ba ferrite particles obtained by heat treatment at 900°C, and Figure 6 shows the case of 5i (IV) untreated, and Figure 7 shows the case of 5i (IV). (IV) This is a case of processing. 90
It can be seen that the growth and sintering of each particle is significantly hindered by the presence of 5i(IV) at a high temperature of 0°C. The sintering start temperature of each particle depends on the type of atmosphere and the dissolved 5i (I
V) It was economically effective at temperatures of 900° C. or lower, although it depended on the amount of adsorption 5i (IV) due to concentration and pH. [0025tFigure 8 shows the BET specific surface area (S) value of 40 to 6.
B aF e+2-2M T with 0 m2 g-1
By heat-treating the i 0+9 sample in air at a temperature of 600°C for 2 hours, the obtained S value is 30 to 50 m2.
g-1, the Hc value of a heat-treated sample having a magnetization (M) value of 43 to 45 emug-1 is plotted against composition X. As is clear from Figure 8, Hc has an X value of 0.6 to 1.
．． It can be controlled within the range of 2 to 500-10000e. [0026]

[Examples] Next, the present invention will be explained with reference to Examples and Comparative Examples. [0027] In addition, the specific surface area value of the particles in the examples is N
This is a value measured by the BET method using 2. In addition, the magnetization value was measured in a powder state in a magnetic field of 10 KOe, and the coercive force was measured at a filling degree of 1.6 g/cm.
This is the value measured in 3. [0028tExample I Fe (NOa) a 14mo 1, Co (N
0.807 m each of O3) 2 and T i C14
ol and Ba(OH)2 8H201,76mol and N
165 mol of aOH was added to 20 1 of CO2-free water in an autoclave, heated to 270°C, and maintained at this temperature for 5 hours with mechanical stirring to form a ferromagnetic brown precipitate. [0029] After cooling to room temperature, the ferromagnetic brown precipitate was filtered off and the adsorbed Ba (II) was removed by treatment with 3M HClO4101 three times.

[0030] As a result of electron microscopic observation, the obtained ferromagnetic brown particle powder was found to be hexagonal plate-shaped particles with a uniform particle size and each particle separated, and the diameter was 0.2 to 0.4 μm.
, plate ratio 22-44, and as a result of fluorescent X-ray analysis, Ba
The composition was Fe+o76COo62Tio620+9. Further, the specific surface area (S) value is 46 m2 g-1, the magnetization (M) value is 28 emug-', and the coercive force Hc
The value was 3680e.

Next, the ferromagnetic brown particles were treated with an aqueous solution containing 5% by weight of water glass, filtered and dried, and then heated in air at 800°C. Ferromagnetic BaFe+o4s C0o62Ti obtained by heat treatment
o, the specific surface area (S) value of 52019 fine particle powder is 43 m
2g-', and the magnetization (M) value is 47 emu g-1
The coercive force Hc value was 7500e. Also,
As a result of electron microscopy, the particle size was uniform, and the particles were hexagonal plate-shaped particles that were separated one by one, and the diameter was 0.2 to 0.4.
μm and plate ratio were 20 to 44. [0032] Example 2 Fe (NO3) 314 mol, Co (NO3)2
and 1.235 mol each of T i Cl 4 and 1.75 mol of Ba(OH) 2 8H and NaOH 1
69 mol was added to water 201 from which CO2 had been removed in an autoclave, heated to 300°C, and treated in the same manner as in Example 1 to generate a ferromagnetic brown precipitate. [0033] As a result of electron microscopy observation, the obtained ferromagnetic brown particles were found to be hexagonal plate-shaped particles with uniform particle size and each particle having a diameter of 0. 1~0.2μ
m, plate ratio 11-25, and as a result of fluorescent X-ray analysis, B
The composition was aFe+o2o C0o9oTio9oO+9. Further, the specific surface area (S) value was 52 m2 g-1, the magnetization (M) value was 33.4 emug-1, and the coercive force (Hc) value was 1150e. [0034] Next, the ferromagnetic brown particles were subjected to Si treatment in the same manner as in Example 1, followed by heat treatment. BaFe+o2o CO obtained by heat treatment
o,90T i O,90019 fine particle powder has a specific surface area (S) value of 46 m2g −1 and a magnetization (M) value of 5.
1 emug-' and the coercive force (Hc) value is 570 0
It was e. Furthermore, as a result of electron microscopy, the particles were found to be hexagonal plate-like particles with uniform particle size and individual particles, with a diameter of 0.1 to 0.2 μm and a plate ratio of 10 to 22. [0035] Example 3 A ferromagnetic brown precipitate was produced in the same manner as in Example 1 except that 0°404 mol of each of Co (II) and Zn was used as divalent metal ions. [0036] As a result of electron microscopy observation, the obtained ferromagnetic brown particle powder was found to be hexagonal plate-shaped particles with uniform particle size and individual particles, and the diameter was 0.2 to 0.4 μm.
, plate ratio 20-44, and as a result of fluorescent X-ray analysis, Ba
Fe+o7e COo, s+Zno3+Tio, s20
The composition was +9. In addition, the specific surface area (S) value is 43
．． 3 m” g-', and the magnetization (M) value is 35.5.
emug-1 with a coercive force (Hc) value of 6880e
Met. [0037] Next, the ferromagnetic brown particles were subjected to Si treatment in the same manner as in Example 1, and then heat treated at 700°C. BaFe+o7 obtained by heat treatment
The specific surface area (S) value of sCoo31Zno31Tio62019 fine particle powder is 40 m2g-', and the magnetization (M)
The value is 52 emug-1 and the coercive force (Hc) value is 9.
It was 600e. In addition, as a result of electron microscopy, the particle size was uniform, and each particle was a hexagonal plate-shaped particle, the diameter was 0.2 to 0.4 μm, and the plate ratio was 20 to 40.
Met. [0038] Example 4 Mn (I I) 0.4 instead of Zn (I I)
A ferromagnetic brown precipitate was produced in the same manner as in Example 3, except that 04 mol was used. [0039] As a result of electron microscopy observation, the obtained ferromagnetic brown particle powder was found to be hexagonal plate-shaped particles with uniform particle size and individual particles, and the diameter was 0.2 to 0.4 μm.
, the plate ratio is 20 to 40, and as a result of fluorescent X-ray analysis, Ba
Fe+o4e Mno3+CO0,31Tio620+
The composition was 9. Moreover, the specific surface area (S) value is 40.
2m2g-', and the magnetization (M) value is 31.2emu
g-' and the coercive force (Hc) value was 5800e. [00401 Next, the above ferromagnetic brown particles were subjected to Si treatment in the same manner as in Example 1, and then heated at 900 °C in a N2 atmosphere.
Heat treatment was performed at ℃. BaFe1076Mn031COO31Ti06201 obtained by heat treatment
The specific surface area (S) value of the 9 fine particle powder was 32 m2 g', the magnetization (M) value was 52 emu g-', and the coercive force (Hc) value was 985 Oe. In addition, as a result of electron microscopy, the particle size was uniform, and each particle was a hexagonal plate-shaped particle with a diameter of 0.2 to 0.4 μm.
The plate ratio was 14-31. [00411] [Effects of the Invention] According to the method for producing hexagonal plate-shaped Ba ferrite particles according to the present invention, as shown in the above example, the powder has an appropriate coercive force and a large magnetization value, and has good orientation. Since a hexagonal plate-shaped Ba ferrite particle powder having excellent dispersibility can be obtained, it is suitable as a magnetic particle powder for magnetic recording, particularly for perpendicular magnetic recording. [0042]

[Brief explanation of the drawing]

Figures 1 and 2 show BaFe+o, 5COo, and e, respectively.
TiO, 6019 and BaFe9. sTi1. +
The (M) value and Hc value when COI and I019 are heated in the air at temperatures of 300° C. to 900° C. for 2 hours are plotted against the treatment temperature. In the figure, ○ mark is BaF
e+o, 5COo, e Tio, s O19, ・mark is B
aFe9. This is the case using s Tit, + COI, I 019. [0043] Figure 3 shows BaFe+o, 5CO as a representative example.
5i(I) when using o7sT i O,75019
This figure shows the processing temperature dependence of the S value depending on the presence or absence of V). [0044] FIGS. 4 to 7 are electron micrographs (X 100
000). 4 and 5 show Ba ferrite particles obtained by heat treatment at 800°C,
Figure 4 shows 5i (IV) untreated, Figure 5 shows 5i (IV)
This is the case when it is processed. Figures 6 and 7 show Ba ferrite particles obtained by heat treatment at 900°C; Figure 6 shows 5i (IV) untreated, and Figure 7 shows 5t (I
V) In the case of processing. [0045tFigure 8 shows BaFe+2-CoTi
The S value obtained by heat-treating the 019 particle powder in air at a temperature of 600°C for 2 hours is 30 to 50 m2g-
1. HC values of heat-treated samples with magnetization (M) values of 43 to 45 emug-1 are plotted against composition X.

[Figure 1]

[Figure 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 8]

Claims (1)

[Claims] 1. A hexagonal plate for magnetic recording, characterized in that hexagonal plate-shaped Ba ferrite fine particles are generated from an aqueous solution, the fine particles are treated with an aqueous solution containing 5i (IV), and then heat-treated at a temperature of 900° C. or less. A method for producing Ba-like ferrite fine particle powder.