JP2020038963A - Ferrite powder for bond magnet and method for manufacturing the same - Google Patents

Abstract

To provide a ferrite powder for a bond magnet with which a bond magnet having a high residual magnetization Br can be obtained through magnetic field orientation, and a method for manufacturing the same.SOLUTION: A powder of complex oxide of iron, strontium, lanthanum, and cobalt, and iron oxide are mixed and granulated and then calcined, and a roughly pulverized powder obtained by roughly pulverizing a calcined product obtained through the calcination is pulverized and annealed, thereby manufacturing a ferrite powder for a bond magnet having a composition of (SrLa) (FeCo)O(wherein 0<x≤0.5, 0<y≤0.04, 10.0≤n≤12.5, -1.0≤z≤3.5) and having an average particle diameter of 1.3 to 2.5 μm.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a ferrite powder for a bonded magnet and a method for producing the same, and more particularly to a ferrite powder for a bonded magnet containing coarse and fine ferrite particles and a method for producing the same.

  Conventionally, ferrite-based sintered magnets have been used as high-magnetism magnets such as small motors used for AV equipment, OA equipment, and automotive electrical parts, and magnets used for magnet rolls of copiers. . However, the ferrite-based sintered magnet has a problem that chipping cracks are generated and the productivity is inferior because polishing is required. In addition, there is a problem that processing into a complicated shape is difficult.

  Therefore, in recent years, bond magnets of rare-earth magnets have been used as high-magnetism magnets for small motors and the like used for AV equipment, OA equipment, automotive electrical components, and the like. However, rare earth magnets cost about 20 times as much as ferrite-based sintered magnets and have a problem that they are easily rusted. Therefore, it is desired to use ferrite-based bonded magnets instead of ferrite-based sintered magnets. I have.

As the ferrite powder for this bonded magnet composition is _{(Sr 1-x A x)} O · n [(Fe 1-y-z Co y Zn z) 2 O 3] ( where, A is La, La-Nd , La-Pr or La-Nd-Pr, n = 5.80-6.10, x = 0.1-0.5, y = 0.0083-0.042, 0 ≦ z <0.0168). there are, saturation magnetization value σs is ^{73Am 2 / kg (73emu / g} ) or more the average particle diameter of 1.0~3.0μm magnetoplumbite type strontium ferrite particles is, and magnetoplumbite-type strontium ferrite There has been proposed a strontium ferrite particle powder for a bonded magnet in which the particle powder contains 60% or more of plate-like particles in a number ratio (for example, see Patent Document 1).

JP-A-2002-175907 (paragraph number 0025)

  However, the strontium ferrite particle powder for a bonded magnet of Patent Document 1 contains a large amount of plate-like particles. Therefore, if the particle powder is aligned in the magnetic field direction by magnetic field orientation, the plate-like particles hinder each other. Therefore, it has been difficult to produce a bonded magnet having high orientation.

  Accordingly, an object of the present invention is to provide a ferrite powder for a bonded magnet and a method for producing the same, which can obtain a bonded magnet having a high remanent magnetization Br due to magnetic field orientation in view of such conventional problems. .

  The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result of mixing and granulating iron, strontium, lanthanum and cobalt composite oxide powder, and iron oxide, followed by firing, The present inventors have found that a bonded magnet having a high remanent magnetization Br can be obtained by magnetic field orientation, and have completed the present invention.

  That is, the method for producing a ferrite powder for a bonded magnet according to the present invention is characterized in that a powder of a composite oxide of iron, strontium, lanthanum and cobalt, and iron oxide are mixed, granulated, and then fired.

  In this method for producing a ferrite powder for a bonded magnet, it is preferable to anneal after coarsely pulverized powder obtained by coarsely pulverizing a fired product obtained by firing. In addition, the powder of the composite oxide is obtained by mixing strontium carbonate, lanthanum oxide, iron oxide, and cobalt oxide, granulating the mixture, and sintering the resultant at 1000 to 1250 ° C. to obtain a crushed product. Is preferred. Further, it is preferable that firing after mixing and granulating the composite oxide powder and iron oxide is performed at 1100 to 1400 ° C. Further, when mixing the composite oxide powder and the iron oxide, the composite oxide is mixed such that the molar ratio Fe / (Sr + La) of Fe in the iron oxide with respect to the sum of Sr and La becomes 4.5 to 11.7. It is preferred to mix iron oxide and iron oxide.

Also, the ferrite powders for bonded magnet according to the present _{invention, (Sr 1-x La x} ) · (Fe 1-y Co y) n O 19-z ( where, 0 <x ≦ 0.5,0 <y ≦ 0 0.04, 10.0 ≦ n ≦ 12.5, −1.0 ≦ z ≦ 3.5, and the average particle size is 1.3 to 2.5 μm.

The ferrite powder for a bonded magnet preferably has a specific surface area of 1.0 to 2.1 m ² / g, and a ratio of a long axis to a short axis of a particle having a long axis of 1.0 μm or more (long axis). It is preferable that the average value of (long / short axis length) is 1.55 or less. Also, 90.0 parts by mass of ferrite powder for a bonded magnet, 0.8 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 8.4 parts by mass of a powdery polyamide resin were charged into a mixer. The mixture obtained by mixing is kneaded at 230 ° C. to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets are injected at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm ² in a magnetic field of 9.7 kOe. When a bond magnet having a diameter of 15 mm and a height of 8 mm was formed to form a cylindrical bond magnet (the orientation direction of the magnetic field was along the central axis of the cylinder), and the residual magnetization Br of the bond magnet was measured with a measurement magnetic field of 10 kOe. Preferably, the residual magnetization Br is 2950 G or more. Further, when the maximum energy product BH _max of the above-mentioned bonded magnet is measured with a measurement magnetic field of 10 kOe, it is preferable that the maximum energy product BH _max is not less than 2.15 MGOe.

  Further, a bonded magnet according to the present invention includes the ferrite powder for a bonded magnet described above and a binder.

  ADVANTAGE OF THE INVENTION According to this invention, the ferrite powder for bond magnets which can obtain the bond magnet which has high remanent magnetization Br by magnetic field orientation can be manufactured.

FIG. 3 is a view showing a measurement result of a ferrite powder for a bonded magnet obtained in Example 1 by a powder X-ray diffraction method (XRD). 3 is a scanning electron microscope (SEM) photograph of a cross section of the bonded magnet obtained in Example 1. 4 is an SEM photograph of a cross section of the bonded magnet obtained in Comparative Example 1.

In the embodiment of the method for producing a ferrite powder for a bonded magnet according to the present invention, a powder of a composite oxide of iron, strontium, lanthanum and cobalt, and iron oxide (preferably hematite (α-Fe ₂ O ₃ )) are used. After mixing and granulating so that Fe / (Sr + La) in iron oxide with respect to the sum of Sr and La is preferably 4.5 to 11.7, and more preferably 9.0 to 11.0. Preferably at 1100 to 1400 ° C, more preferably at 1100 to 1300 ° C, and most preferably at 1150 to 1250 ° C), and after crushing the crushed product obtained by crushing the calcined product obtained by the calcination, (Preferably at 950 to 1000 ° C.).

  The powder of the composite oxide of iron, strontium, lanthanum, and cobalt is mixed with strontium carbonate, lanthanum oxide, iron oxide, and cobalt oxide, and then granulated. It can be obtained by pulverizing a calcined product obtained by calcining at 1200 ° C, most preferably at 1050 to 1150 ° C.

  The above coarsely pulverized powder is pulverized (wet pulverization) with a wet attritor or the like (preferably for 20 to 80 minutes), the obtained slurry is filtered, and the solid obtained is dried. It is preferable to anneal after crushing the cake obtained by crushing the cake with a mixer using a vibrating ball mill or the like.

In this way, (Sr _1-x La _x ) · (Fe _1-y Co _y ) _n O _19-z (where 0 <x ≦ 0.5, 0 <y ≦ 0.04, 10.0 ≦ n ≦ 12.5, −1.0 ≦ z ≦ 3.5) Ferrite powder for a bonded magnet having a composition represented by the following formula:

Further, the embodiment of the ferrite powder for a bonded magnet according to the present invention is as follows: (Sr _1-x La _x ) · (Fe _1-y Co _y ) _n O _19-z (where 0 <x ≦ 0.5 (preferably Is 0.03 ≦ x ≦ 0.5, more preferably 0.1 ≦ x ≦ 0.5), 0 <y ≦ 0.04 (preferably 0.004 ≦ y ≦ 0.04), 10.0 ≦ n ≦ 12.5 (preferably 10.0 ≦ n ≦ 12.0), −1.0 ≦ z ≦ 3.5 (preferably −0.5 ≦ z ≦ 3.5), The average particle size is 1.3 to 2.5 μm (preferably 1.3 to 2.0 μm).

The specific surface area of the ferrite powder for a bonded magnet is preferably 1.0 to 2.1 m ² / g, and more preferably 1.2 to 2.0 m ² / g.

Further, the density of the ferrite powder for a bonded magnet when 10 g of the ferrite powder for a bonded magnet is filled in a cylindrical mold having an inner diameter of 2.54 cmφ and then compressed at a pressure of 1 ton / cm ² is determined by the compression of the ferrite powder for a bonded magnet. When measured as density (CD), the compressed density (CD) is preferably from 3.0 to 4.0 g / cm ³ , more preferably from 3.2 to 3.6 g / cm ³ .

Further, 8 g of the ferrite powder for bond magnet and 0.4 cc of the polyester resin were kneaded in a mortar, and 7 g of the obtained kneaded material was filled in a mold having an inner diameter of 15 mmφ, and compressed at a pressure of 2 ton / cm ² for 60 seconds. The obtained molded product was extracted from the mold and dried at 150 ° C. for 30 minutes to produce a green compact. The magnetic properties of the green compact were measured using a BH tracer at a measurement magnetic field of 10 kOe. When the coercive force iHc and the residual magnetization Br are measured, the coercive force iHc is preferably 2000 to 4000 Oe, more preferably 2300 to 3500 Oe, and the residual magnetization Br is preferably 1700 to 2000 G, more preferably 1800 to 1950 G. .

  In general, a ferrite magnetic material having a magnetoplumbite type crystal structure has a remanent magnetization Br of a negative temperature coefficient, a coercive force Hc of a positive temperature coefficient, and a coercive force Hc of 0.2 to 0.3. % / ° C. is known. That is, a ferrite magnetic material having a magnetoplumbite type crystal structure has a lower coercive force Hc as the temperature becomes lower. Therefore, when used in a bonded magnet, a ferrite magnetic material having a coercive force Hc higher than necessary is required. If not used, there is a problem that irreversible demagnetization (low temperature demagnetization) occurs due to a temperature cycle from a low temperature to a high temperature. Such low-temperature demagnetization of ferrite magnetic material is a problem particularly when ferrite magnetic material is used as a material for bonded magnets used in outdoor units for air conditioners and motors for automobiles, which are greatly affected by temperature fluctuations outdoors. become. Therefore, 20 mg of the ferrite powder for bond magnet and 10 mg of paraffin are packed in a cell for measurement, kept at 60 ° C. for 10 minutes, and then cooled to fix the ferrite powder for bond magnet in the cell for measurement. The coercive force of the powder was measured at three points of −25 ° C., 0 ° C. and 25 ° C. by a full loop (sweeping speed 200 Oe / sec) applying a magnetic field up to 5T (10,000 Oe). It is preferable that the calculated temperature coefficient of the coercive force Hc of the ferrite powder for a bonded magnet is 0.1% / ° C. or less.

Also, 90.0 parts by mass of ferrite powder for a bonded magnet, 0.8 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 8.4 parts by mass of a powdery polyamide resin were charged into a mixer. The mixture obtained by mixing is kneaded at 230 ° C. to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets are injected at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm ² in a magnetic field of 9.7 kOe. Then, a cylindrical bond magnet having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field is along the central axis of the cylinder) is produced, and the coercive force iHc, residual magnetization Br, and maximum energy product of the bond magnet are produced. When BH _max is measured with a measurement magnetic field of 10 kOe, the coercive force iHc is 2200 to 3700 Oe, more preferably 2400 to 3500 Oe, and the residual magnetization Br is preferably 295 It is 0 G or more, more preferably 2970 G or more, and the maximum energy product BH _max is preferably 2.15 MGOe or more, more preferably 2.2 to 2.5 MGOe.

Furthermore, the above bond magnet is cut in parallel to the direction of the applied magnetic field, the shape of the particles is observed with an electron microscope at a magnification of 2000 times, and the obtained electron micrograph is binarized to obtain a shape index of the particles. The major axis length (the maximum value of the distance between straight lines when one particle is sandwiched between two parallel straight lines (the length of a line segment drawn perpendicular to the two parallel straight lines)) is 1.0 μm The ratio of the major axis length to the minor axis length (the minimum value of the distance between straight lines when one particle is sandwiched between two parallel straight lines) (long axis length / short axis length) (aspect ratio) is determined. (Assuming each particle to be a plate-like particle, and calculating the volume-average aspect ratio weighted by volume, where the volume is defined as major axis length × major axis length × minor axis length), the aspect ratio is 1.55 or less. It is preferred that If the aspect ratio is 1.55 or less, it is easy to align the particles of the ferrite powder for a bonded magnet in the direction of the magnetic field by the magnetic field orientation, and a bonded magnet having a high particle orientation and a high residual magnetization Br and a high maximum energy product BH _max is obtained. It becomes easy to manufacture.

  Hereinafter, examples of the ferrite powder for a bonded magnet and the method for producing the same according to the present invention will be described in detail.

[Example 1]
(Production of coarse ground powder)
Strontium carbonate (SrCO ₃ , specific surface area 5.8 m ² / g), lanthanum oxide (La ₂ O ₃ , specific surface area 3.8 m ² / g) and hematite (as iron oxide) (α-Fe ₂ O ₃ , specific ratio) Surface area 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) molar ratio Sr: La: Fe: Co = 0.70: 0.30: 0.70: 0 The mixture was weighed and mixed so as to obtain a granulated product having a diameter of 3 to 10 mm into an internal-combustion-type rotary kiln. Firing (primary firing) at 1100 ° C. for 20 minutes in an atmosphere gave a fired product. The fired product was pulverized with a roller mill to obtain a powder of a composite oxide of iron, strontium, lanthanum, and cobalt. The specific surface area of the composite oxide powder was measured by a BET one-point method using a specific surface area measuring device (Monosorb manufactured by Cantachrome), and the specific surface area was 3.5 m ² / g.

This composite oxide powder and hematite (as iron oxide) (α-Fe ₂ O ₃ , specific surface area 5.3 m ² / g) were converted into a molar ratio (Fe / (Sr + La) in the oxide with respect to the sum of Sr and La. )) = 10.0 and weighed and mixed, 0.17% by weight of boric acid and 2.3% by weight of potassium chloride (as additives) were added to the mixture and mixed, Water is added for granulation, and the obtained spherical granules having a diameter of 3 to 10 mm are put into an internal combustion type rotary kiln, and fired (second firing) at 1250 ° C. (firing temperature) in the air for 20 minutes. The obtained fired product was pulverized with a roller mill to obtain a coarsely pulverized powder.

(Manufacture of ferrite powder for bonded magnets)
100 parts by mass of the obtained coarsely pulverized powder and 150 parts by mass of water were put into a wet attritor, and pulverized for 20 minutes to obtain a slurry. The solid obtained by filtering this slurry was dried in the air at 150 ° C. for 10 hours to obtain a dried cake. The crushed product obtained by crushing the dried cake with a mixer is crushed by a vibration ball mill (Uras Vibrator KEC-8-YH manufactured by Murakami Seiki Seisakusho Co., Ltd.) using a steel ball having a diameter of 12 mm as a medium. The crushing treatment was performed at a rotation speed of 1800 rpm and an amplitude of 8 mm for 20 minutes. The pulverized material thus obtained was annealed (annealed) at 985 ° C. for 30 minutes in the air using an electric furnace to obtain a ferrite powder for a bonded magnet.

With respect to the ferrite powder for a bonded magnet, the composition analysis is performed by calculating the component amounts of the respective elements by a fundamental parameter method (FP method) using a fluorescent X-ray analyzer (ZSX100e manufactured by Rigaku Corporation). went. In this composition analysis, a ferrite powder for a bonded magnet was packed in a cell for measurement, and a pressure of 10 ton / cm ² was applied for 20 seconds to mold, a measurement mode was an EZ scan mode, a measurement diameter was 30 mm, and a sample form was an oxide. After performing qualitative analysis in a vacuum atmosphere with the measurement time as a standard time, quantitative analysis was performed on the detected constituent elements. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.3% by mass of MnO, 85.3% by mass of Fe ₂ O ₃ , and 2.4% by mass Of Co ₂ O ₃ , 6.8% by mass of SrO, 0.1% by mass of BaO, and 4.9% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.3% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is expressed as (Sr ₁₋ ) from the analytical values of Sr, La, Fe, and Co, which are the main components. _{x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.026, n = 11. 5, z = 0.79. In addition, z is +2 for the valence of Sr, +3 for the valence of La, +3 for the valence of Fe, +2 for the valence of Co, and -2 for the valence of O. (Zero).

Further, with respect to the ferrite powder for a bonded magnet, using a powder X-ray diffractometer (Rigaku Miniflex600), a tube voltage of 40 kV, a tube current of 15 mA, a measurement range of 15 ° to 60 °, and a scan speed of The measurement was performed by powder X-ray diffraction (XRD) at 1 ° / min and a scan width of 0.02 °. FIG. 1 shows the measurement results. Note that the lower side of FIG. 1 shows the peak position of SrFe ₁₂ O ₁₉ having a general M-type ferrite structure. From FIG. 1, all peaks were observed at the same position as SrFe ₁₂ O _19, and it was confirmed that the ferrite powder for a bonded magnet of this example had an M-type ferrite structure. This result was the same in Examples 2 to 8 and Comparative Examples 1 to 3 described below.

The average particle size (APD) of the ferrite powder for a bonded magnet was measured by an air permeation method using a specific surface area measuring device (SS-100 manufactured by Shimadzu Corporation). The average particle size was 1.72 μm. Was. When the specific surface area of the ferrite powder for a bonded magnet was measured by the same method as described above, the specific surface area was 1.47 m ² / g.

Further, the density of the ferrite powder for a bonded magnet when 10 g of the ferrite powder for a bonded magnet is filled in a cylindrical mold having an inner diameter of 2.54 cmφ and then compressed at a pressure of 1 ton / cm ² is determined by the compression of the ferrite powder for a bonded magnet. It was 3.45 g / cm < ³ > when measured as density (CD).

Further, 8 g of ferrite powder for bond magnet and 0.4 cc of polyester resin (P-resin manufactured by Nihon Geikagaku Co., Ltd.) were kneaded in a mortar, and 7 g of the obtained kneaded material was filled in a mold having an inner diameter of 15 mmφ. The molded product obtained by compressing at a pressure of / cm ² for 60 seconds was extracted from the mold and dried at 150 ° C. for 30 minutes to obtain a green compact. The coercive force iHc and residual magnetization Br of the green compact were measured using a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.) at a measurement magnetic field of 10 kOe. iHc was 3060 Oe and residual magnetization Br was 1870G.

  In addition, 20 mg of ferrite powder for bond magnet and 10 mg of paraffin were packed in a cell for measurement, held at 60 ° C. for 10 minutes, and then cooled to fix the ferrite powder for bond magnet in the cell for measurement. (VSM-5HSC manufactured by Toei Kogyo Co., Ltd.), the coercive force of the ferrite powder for a bonded magnet was set to -25 ° C. by a full loop (sweep application speed of 200 Oe / sec) applying a magnetic field up to 5 T (10,000 Oe). And 0 ° C. and 25 ° C., and the temperature coefficient of the coercive force Hc was calculated from the rate of change of the coercive force Hc. As a result, the temperature coefficient of the coercive force Hc of the ferrite powder for a bonded magnet was −0.024% / ° C. Note that this temperature coefficient was obtained by determining the coercive force Hc as y and the temperature as x, obtaining the relational expression between y and x by the least square method, and calculating the slope of the relational expression.

(Manufacture of bonded magnets)
90.0 parts by mass of the obtained ferrite powder for a bonded magnet, 0.8 parts by mass of a silane coupling agent (Z-6094N manufactured by Toray Dow Corning Co., Ltd.), and a lubricant (VPN-212P manufactured by Henkel Co.) were added. 8 parts by mass and 8.4 parts by mass of a powdery polyamide resin (P-1011F manufactured by Ube Industries, Ltd.) are weighed, filled in a mixer and mixed, and the mixture obtained is kneaded at 230 ° C. To obtain a kneaded pellet having an average diameter of 2 mm. The kneaded pellets were loaded into an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.), and injection-molded at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm ² in a magnetic field of 9.7 kOe, and a diameter of 15 mm × high An 8 mm-thick cylindrical bonded magnet (FC: 90.0% by mass, 9.7 kOe) (the orientation direction of the magnetic field is along the central axis of the cylinder) was obtained.

Using a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.), the coercive force iHc, residual magnetization Br and maximum energy product BH _max of the bond magnet were measured at a measurement magnetic field of 10 kOe as the magnetic properties of the bond magnet. However, the coercive force iHc was 3017 Oe, the residual magnetization Br was 3069 G, and the maximum energy product BH _max was 2.33 MGOe.

  Further, the bonded magnet was cut in parallel to the direction of the applied magnetic field, the shape of the particles was observed at a magnification of 2000 with a scanning electron microscope (SEM), and the obtained SEM photograph was binarized to obtain the particles. As the shape index, the length of the major axis of the 200 or more particles in the SEM photograph (the long axis length at which the entire outer edge portion is observed in one or more visual fields of the SEM photograph (between straight lines when one particle is sandwiched between two parallel straight lines) The ratio of the major axis length to the minor axis length (minimum value of the distance between straight lines when one particle is interposed between two parallel straight lines) for 200 or more particles having a maximum value of 1.0 μm or more). The average value (aspect ratio) of (long axis length / short axis length) was found to be 1.43. In addition, as this aspect ratio, assuming that each particle is a plate-like particle, and calculating the volume as the major axis length × the major axis length × the minor axis length, the volume average aspect ratio weighted by the volume was calculated.

[Example 2]
A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1, except that the pulverization time by a wet attritor was set to 40 minutes.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 85.1% by mass of Fe ₂ O ₃ , and 2.5% by mass and of _Co 2 _{O 3,} and 0.1 wt% of ZnO, and 6.7 wt% SrO, and 0.1 wt% BaO, includes a 4.9 wt% _La 2 _{O 3,} Sr, La, Fe, and Co, which were main components of the ferrite powder for a bonded magnet, were detected. In addition, elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.4% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.028, n = 11. 6, z = 0.64.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.62 μm, the specific surface area was 1.62 m ² / g, the compression density (CD) was 3.40 g / cm ³ , the coercive force iHc of the compact was 3130 Oe, and the residual magnetization Br was 1870 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 3052Oe, remanence Br is 3038G, The maximum energy product BH _max was 2.28 MGOe, and the aspect ratio was 1.54.

[Example 3]
A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1, except that the pulverization time by a wet attritor was set to 80 minutes.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 85.0% by mass of Fe ₂ O ₃ , and 2.5% by mass of Of Co ₂ O ₃ , 0.1% by mass of ZnO, 6.7% by mass of SrO, 0.1% by mass of BaO, and 5.0% by mass of La ₂ O ₃ , Sr, La, Fe, and Co, which were main components of the ferrite powder for a bonded magnet, were detected. In addition, elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.4% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.028, n = 11. 5, z = 0.79.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.42 μm, the specific surface area was 1.96 m ² / g, the compression density (CD) was 3.42 g / cm ³ , the coercive force iHc of the compact was 3310 Oe, and the residual magnetization Br was 1870 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 3193Oe, remanence Br is 3036G, The maximum energy product BH _max was 2.28 MGOe, and the aspect ratio was 1.50.

[Example 4]
A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1 except that the temperature for the secondary firing was set at 1150 ° C.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 85.0% by mass of Fe ₂ O ₃ , and 2.6% by mass Of Co ₂ O ₃ , 6.8% by mass of SrO, 0.1% by mass of BaO, and 4.9% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. In addition, elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.4% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.31, y = 0.029, n = 11. 5, z = 0.83.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.53 μm, the specific surface area was 1.65 m ² / g, the compression density (CD) was 3.29 g / cm ³ , the coercive force iHc of the compact was 3410 Oe, and the residual magnetization Br was 1820 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 3407Oe, remanence Br is 2985 grams, The maximum energy product BH _max was 2.21 MGOe, and the aspect ratio was 1.54.

[Example 5]
The same composite oxide powder as in Example 1 and hematite (as iron oxide) (α-Fe ₂ O ₃ , specific surface area 5.3 m ² / g) were mixed with Fe in iron oxide with respect to the sum of Sr and La. A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1, except that the mixture was weighed and mixed so that the molar ratio (Fe / (Sr + La)) = 10.4.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.4% by mass of MnO, 85.7% by mass of Fe ₂ O ₃ , 2.4% by mass of Co ₂ O ₃ , and 0.1% by mass of Of ZnO, 6.5% by mass of SrO, 0.1% by mass of BaO, and 4.7% by mass of La ₂ O ₃ . La, Fe, and Co were detected. Note that elements such as Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were as small as 0.4 mass% in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.31, y = 0.026, n = 12. 0, z = −0.04.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.70 μm, the specific surface area was 1.56 m ² / g, the compression density (CD) was 3.40 g / cm ³ , the coercive force iHc of the compact was 2780 Oe, and the residual magnetization Br was 1890 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. For this bonded magnet, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. As a result, the coercive force iHc was 2546 Oe, the residual magnetization Br was 3009 G, The maximum energy product BH _max was 2.23 MGOe, and the aspect ratio was 1.53.

[Example 6]
Strontium carbonate (SrCO _3, a specific surface area of 5.8 m ² / g) and lanthanum oxide _(La 2 _{O 3,} a specific surface area of 3.8 m ² / g) and hematite _(α-Fe 2 _{O 3,} a specific surface area of 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) such that the molar ratio is Sr: La: Fe: Co = 0.70: 0.30: 0.85: 0.15. A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1 except for weighing and mixing.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.3% by mass of MnO, 86.4% by mass of Fe ₂ O ₃ , and 1.2% by mass Of Co ₂ O ₃ , 6.7% by mass of SrO, 0.1% by mass of BaO, and 5.0% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.3% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.014, n = 11. 5, z = 0.73.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.87 μm, the specific surface area was 1.27 m ² / g, the compression density (CD) was 3.43 g / cm ³ , the coercive force iHc of the compact was 2650 Oe, and the residual magnetization Br was 1880 G. there were. Further, the coercive force Hc of the ferrite powder for a bonded magnet was measured in the same manner as in Example 1, and the temperature coefficient of the coercive force Hc was calculated to be -0.063% / ° C.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2724Oe, remanence Br is 3038G, The maximum energy product BH _max was 2.29 MGOe, and the aspect ratio was 1.52.

[Example 7]
A ferrite powder for a bonded magnet was obtained in the same manner as in Example 6, except that the temperature for the secondary firing was 1300 ° C.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.3% by mass of MnO, 86.5% by mass of Fe ₂ O ₃ , and 1.2% by mass Of Co ₂ O ₃ , 6.7% by mass of SrO, 0.1% by mass of BaO, and 5.0% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.3% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.013, n = 11. 5, z = 0.61.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.84 μm, the specific surface area was 1.36 m ² / g, the compression density (CD) was 3.49 g / cm ³ , the coercive force iHc of the compact was 2390 Oe, and the residual magnetization Br was 1910 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2473Oe, remanence Br is 3043G, The maximum energy product BH _max was 2.29 MGOe, and the aspect ratio was 1.49.

Example 8
A ferrite powder for a bonded magnet was obtained in the same manner as in Example 6, except that the temperature of the secondary firing was 1200 ° C.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.3% by mass of MnO, 86.2% by mass of Fe ₂ O ₃ , 1.3% by mass of Co ₂ O ₃ , and 0.2% by mass of Contains 6.8% by mass of SrO, 0.1% by mass of BaO, and 5.0% by mass of La ₂ O ₃ . La, Fe, and Co were detected. In addition, elements such as Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.3% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.014, n = 11. 4, z = 0.85.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.71 μm, the specific surface area was 1.49 m ² / g, the compression density (CD) was 3.40 g / cm ³ , the coercive force iHc of the compact was 2870 Oe, and the residual magnetization Br was 1870 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2865Oe, remanence Br is 3061G, The maximum energy product BH _max was 2.32 MGOe, and the aspect ratio was 1.47.

[Example 9]
Except that the composite oxide powder and hematite (as iron oxide) were weighed and mixed such that the molar ratio in the oxide to the sum of Sr and La (Fe / (Sr + La)) = 9.8. A ferrite powder for a bonded magnet was obtained in the same manner as in Example 6.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 85.7% by mass of Fe ₂ O ₃ , and 1.3% by mass of It contains Co ₂ O ₃ , 6.9% by mass of SrO, 0.1% by mass of BaO, and 5.3% by mass of La ₂ O _{3 and} is a main component of the ferrite powder for a bonded magnet. Sr, La, Fe, and Co were detected. Note that elements such as Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.33, y = 0.015, n = 11. 0, z = 1.46.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.90 μm, the specific surface area was 1.32 m ² / g, the compression density (CD) was 3.41 g / cm ³ , the coercive force iHc of the compact was 2840 Oe, and the residual magnetization Br was 1840 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 3038Oe, remanence Br is 3004G, The maximum energy product BH _max was 2.23 MGOe, and the aspect ratio was 1.50.

[Example 10]
Except that the powder of the composite oxide and hematite (as iron oxide) were weighed and mixed such that the molar ratio (Fe / (Sr + La)) in the oxide to the sum of Sr and La was 10.4. A ferrite powder for a bonded magnet was obtained in the same manner as in Example 6.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.4% by mass of MnO, 86.5% by mass of Fe ₂ O ₃ , 1.2% by mass of Co ₂ O ₃ , and 0.2% by mass of Contains 6.7% by mass of SrO, 0.1% by mass of BaO, and 4.8% by mass of La ₂ O ₃ . La, Fe, and Co were detected. Note that elements such as Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.31, y = 0.014, n = 11. 7, z = 0.41.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.97 μm, the specific surface area was 1.21 m ² / g, the compression density (CD) was 3.39 g / cm ³ , the coercive force iHc of the compact was 2540 Oe, and the residual magnetization Br was 1870 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2564Oe, remanence Br is 3013G, The maximum energy product BH _max was 2.24 MGOe, and the aspect ratio was 1.51.

[Example 11]
Strontium carbonate (SrCO _3, a specific surface area of 5.8 m ² / g) and lanthanum oxide _(La 2 _{O 3,} a specific surface area of 3.8 m ² / g) and hematite _(α-Fe 2 _{O 3,} a specific surface area of 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) so that the molar ratio Sr: La: Fe: Co = 0.80: 0.20: 0.80: 0.20 A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1 except for weighing and mixing.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 86.5% by mass of Fe ₂ O ₃ , and 1.6% by mass Of Co ₂ O ₃ , 7.7% by mass of SrO, 0.2% by mass of BaO, and 3.5% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.22, y = 0.018, n = 11. 5, z = 0.67.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.98 μm, the specific surface area was 1.20 m ² / g, the compression density (CD) was 3.40 g / cm ³ , the coercive force iHc of the compact was 2600 Oe, and the residual magnetization Br was 1870 G. there were. Further, the coercive force Hc of the ferrite powder for a bonded magnet was measured in the same manner as in Example 1, and the temperature coefficient of the coercive force Hc was calculated to be 0.020% / ° C.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2748Oe, remanence Br is 3031G, The maximum energy product BH _max was 2.26 MGOe, and the aspect ratio was 1.49.

[Example 12]
Strontium carbonate (SrCO _3, a specific surface area of 5.8 m ² / g) and lanthanum oxide _(La 2 _{O 3,} a specific surface area of 3.8 m ² / g) and hematite _(α-Fe 2 _{O 3,} a specific surface area of 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) such that the molar ratio is Sr: La: Fe: Co = 0.80: 0.20: 0.90: 0.10. A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1 except for weighing and mixing.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1 mass% of Cr ₂ O ₃ , 0.4 mass% of MnO, 87.2 mass% of Fe ₂ O ₃ , and 0.9 mass% of Of Co ₂ O ₃ , 7.9% by mass of SrO, 0.2% by mass of BaO, and 3.2% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.20, y = 0.010, n = 11. 5, z = 0.74.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 2.11 μm, the specific surface area was 1.11 m ² / g, the compression density (CD) was 3.45 g / cm ³ , the coercive force iHc of the compact was 2340 Oe, and the residual magnetization Br was 1890 G. there were. The coercive force Hc of the ferrite powder for a bonded magnet was measured in the same manner as in Example 1, and the temperature coefficient of the coercive force Hc was calculated. As a result, it was 0.052% / ° C.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2371Oe, remanence Br is 3064G, The maximum energy product BH _max was 2.31 MGOe, and the aspect ratio was 1.43.

Example 13
Strontium carbonate (SrCO _3, a specific surface area of 5.8 m ² / g) and lanthanum oxide _(La 2 _{O 3,} a specific surface area of 3.8 m ² / g) and hematite _(α-Fe 2 _{O 3,} a specific surface area of 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) such that the molar ratio is Sr: La: Fe: Co = 0.90: 0.10: 0.90: 0.10. A ferrite powder for a bonded magnet was obtained in the same manner as in Example 1 except for weighing and mixing.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 87.6% by mass of Fe ₂ O ₃ , and 0.9% by mass Of Co ₂ O ₃ , 8.3% by mass of SrO, 0.2% by mass of BaO, and 2.4% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.15, y = 0.010, n = 11. 6, z = 0.53.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 2.01 μm, the specific surface area was 1.09 m ² / g, the compression density (CD) was 3.39 g / cm ³ , the coercive force iHc of the compact was 2290 Oe, and the residual magnetization Br was 1920 G. there were. Further, the coercive force Hc of the ferrite powder for a bonded magnet was measured in the same manner as in Example 1, and the temperature coefficient of the coercive force Hc was calculated to be 0.056% / ° C.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2414Oe, remanence Br is 3038G, The maximum energy product BH _max was 2.27 MGOe, and the aspect ratio was 1.44.

[Example 14]
A ferrite powder for a bonded magnet was obtained in the same manner as in Example 6, except that the primary firing temperature was 1200 ° C.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 86.2% by mass of Fe ₂ O ₃ , and 1.3% by mass Of Co ₂ O ₃ , 6.8% by mass of SrO, 0.1% by mass of BaO, and 5.0% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.014, n = 11. 3, z = 0.90.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.62 μm, the specific surface area was 1.53 m ² / g, the compression density (CD) was 3.40 g / cm ³ , the coercive force iHc of the compact was 3010 Oe, and the residual magnetization Br was 1570 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 3298Oe, remanence Br is 2999G, The maximum energy product BH _max was 2.24 MGOe, and the aspect ratio was 1.49.

[Example 15]
A ferrite powder for a bonded magnet was obtained in the same manner as in Example 6, except that the temperature of the primary firing was set at 1050 ° C.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.4% by mass of MnO, 86.4% by mass of Fe ₂ O ₃ , and 1.3% by mass Of Co ₂ O ₃ , 6.5% by mass of SrO, 0.1% by mass of BaO, and 5.1% by mass of La ₂ O _3. Certain Sr, La, Fe, and Co were detected. Note that elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.34, y = 0.014, n = 11. 7, z = 0.40.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.88 μm, the specific surface area was 1.21 m ² / g, the compression density (CD) was 3.41 g / cm ³ , the coercive force iHc of the compact was 2950 Oe, and the residual magnetization Br was 1850 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. For this bonded magnet, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. As a result, the coercive force iHc was 2880 Oe, the residual magnetization Br was 2998 G, The maximum energy product BH _max was 2.23 MGOe, and the aspect ratio was 1.53.

[Comparative Example 1]
Strontium carbonate (SrCO _3, a specific surface area of 5.8 m ² / g) and lanthanum oxide _(La 2 _{O 3,} a specific surface area of 3.8 m ² / g) and hematite _(α-Fe 2 _{O 3,} a specific surface area of 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) so that the molar ratio Sr: La: Fe: Co = 0.70: 0.30: 11.70: 30.30 Weighed and mixed, a ferrite powder for a bonded magnet was obtained in the same manner as in Example 1 except that the temperature of the primary firing was changed from 1100 ° C. to 1250 ° C. and the secondary firing was not performed.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.3% by mass of MnO, 85.3% by mass of Fe ₂ O ₃ , and 2.4% by mass Of Co ₂ O ₃ , 7.0% by mass of SrO, and 4.9% by mass of La ₂ O ₃ , and Sr, La, Fe, and Co, which are main components of the ferrite powder for a bonded magnet, are contained. was detected. In addition, elements such as Cr and Mn, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.3% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is expressed as (Sr ₁₋ ) from the analytical values of Sr, La, Fe, and Co, which are the main components. _{x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.31, y = 0.026, n = 11. 3, z = 1.12.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.26 μm, the specific surface area was 2.19 m ² / g, the compression density (CD) was 3.34 g / cm ³ , the coercive force iHc of the compact was 3590 Oe, and the residual magnetization Br was 1830 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 3332Oe, remanence Br is 2882G, The maximum energy product BH _max was 2.04 MGOe, and the aspect ratio was 1.56.

[Comparative Example 2]
A ferrite powder for a bonded magnet was obtained in the same manner as in Comparative Example 1 except that the temperature of the primary firing was 1200 ° C.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.3% by mass of MnO, 85.3% by mass of Fe ₂ O ₃ , and 2.4% by mass Of Co ₂ O ₃ , 7.1 mass% of SrO, and 4.7 mass% of La ₂ O ₃ , and Sr, La, Fe, and Co, which are main components of the ferrite powder for a bonded magnet, are contained. was detected. In addition, elements such as Cr and Mn, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.3% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.30, y = 0.026, n = 11. 3, z = 1.09.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.25 μm, the specific surface area was 2.21 m ² / g, the compression density (CD) was 3.26 g / cm ³ , the coercive force iHc of the compact was 3950 Oe, and the residual magnetization Br was 1790 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 3609Oe, remanence Br is 2867G, The maximum energy product BH _max was 2.02 MGOe, and the aspect ratio was 1.62.

[Comparative Example 3]
A ferrite powder for a bonded magnet was obtained in the same manner as in Comparative Example 1, except that the temperature of the primary firing was 1300 ° C.

This ferrite powder for a bonded magnet was subjected to composition analysis in the same manner as in Example 1. As a result, in the ferrite powder for a bonded magnet, 0.1% by mass of Cr ₂ O ₃ , 0.3% by mass of MnO, 85.4% by mass of Fe ₂ O ₃ , and 2.4% by mass Of Co ₂ O ₃ , 7.0 mass% of SrO, and 4.7 mass% of La ₂ O ₃ , wherein Sr, La, Fe, and Co, which are main components of the ferrite powder for a bonded magnet, are contained. was detected. In addition, elements such as Cr and Mn, which are considered to be derived from impurities in the raw material, were also detected, but all were trace amounts of 0.3% by mass in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bond magnet is expressed as (Sr _{1− x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.30, y = 0.026, n = 11. 4, z = 0.95.

The average particle diameter, specific surface area, compression density (CD), coercive force iHc of the compact, and residual magnetization Br were measured for the ferrite powder for a bonded magnet in the same manner as in Example 1. As a result, the average particle size was 1.22 μm, the specific surface area was 2.41 m ² / g, the compression density (CD) was 3.42 g / cm ³ , the coercive force iHc of the compact was 3140 Oe, and the residual magnetization Br was 1800 G. there were.

A bonded magnet was obtained in the same manner as in Example 1 using this ferrite powder for a bonded magnet. This bonded magnet, in the same manner as in Example 1, coercive force iHc, where the residual magnetization Br and maximum energy product _{BH max} was measured to calculate the aspect ratio, the coercive force iHc is 2885Oe, remanence Br is 2930G, The maximum energy product BH _max was 2.11 MGOe, and the aspect ratio was 1.58.

  Tables 1 to 4 show the results of these examples and comparative examples. FIGS. 2 and 3 show scanning electron microscope (SEM) photographs of the cross sections of the bonded magnets obtained in Example 1 and Comparative Example 1, respectively.

  From the results of Examples 1 to 15 and Comparative Examples 1 to 3, in Examples 1 to 15, it is possible to produce a bonded magnet ferrite powder capable of obtaining a bonded magnet having a high residual magnetization Br due to magnetic field orientation. I understand.

Further, the ferrite powders for bonded magnets of Examples 1, 6 and 11 to 13 have a very low temperature coefficient of coercive force Hc of 0.1% / ° C. or less, and are hardly affected by low-temperature demagnetization. It can be seen that it is. In particular, the ferrite powders for bonded magnets of Examples 1 and 6 have excellent negative coercive force Hc temperature coefficients, indicating that they are excellent ferrite powders for bonded magnets that are extremely unlikely to be affected by low-temperature demagnetization. .

Claims (12)

A method for producing a ferrite powder for a bonded magnet, comprising mixing and granulating a powder of a composite oxide of iron, strontium, lanthanum and cobalt, and iron oxide, followed by firing. The method for producing a ferrite powder for a bonded magnet according to claim 1, wherein a coarsely pulverized powder obtained by coarsely pulverizing the calcined product obtained by the calcining is annealed and then annealed. The composite oxide powder is obtained by mixing and granulating strontium carbonate, lanthanum oxide, iron oxide, and cobalt oxide, and then pulverizing a fired product obtained by firing at 1000 to 1250 ° C. The method for producing a ferrite powder for a bonded magnet according to claim 1, wherein: The ferrite for a bonded magnet according to any one of claims 1 to 3, wherein firing after mixing and granulating the composite oxide powder and the iron oxide is performed at 1100 to 1400 ° C. Powder manufacturing method. When mixing the powder of the composite oxide and the iron oxide, the composite is mixed so that the molar ratio Fe / (Sr + La) of Fe in the iron oxide to the sum of Sr and La becomes 4.5 to 11.7. The method for producing a ferrite powder for a bonded magnet according to any one of claims 1 to 4, wherein an oxide powder and the iron oxide are mixed. (Sr _1-x La _x ) · (Fe _1-y Co _y ) _n O _19-z (where 0 <x ≦ 0.5, 0 <y ≦ 0.04, 10.0 ≦ n ≦ 12.5 , -1.0 ≦ z ≦ 3.5), and the average particle diameter is 1.3 to 2.5 μm. Wherein the specific surface area of the ferrite powders for the bond magnet is 1.0~2.1m 2 / ^g, ferrite powder for bonded magnets according to claim 6. The average value of the ratio (major axis length / minor axis length) of the major axis length to the minor axis length of particles having a major axis length of 1.0 μm or more of the ferrite powder for a bonded magnet is 1.55 or less. The ferrite powder for a bonded magnet according to claim 6. 90.0 parts by mass of the ferrite powder for a bonded magnet, 0.8 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 8.4 parts by mass of a powdery polyamide resin are charged into a mixer and mixed. The obtained mixture is kneaded at 230 ° C. to produce a kneaded pellet having an average diameter of 2 mm, and the kneaded pellet is injection-formed at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm ² in a magnetic field of 9.7 kOe. Then, a columnar bond magnet having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field is along the central axis of the column) is produced, and when the residual magnetization Br of the bond magnet is measured with a measurement magnetic field of 10 kOe. The ferrite powder for a bonded magnet according to any one of claims 6 to 8, wherein the residual magnetization Br is 2950G or more. The bond magnet according to any one of claims 6 to 9, wherein when the maximum energy product BH _max of the bond magnet is measured with a measurement magnetic field of 10 kOe, the maximum energy product BH _max is equal to or greater than 2.15 MGOe. For ferrite powder. The ferrite powder for a bonded magnet according to any one of claims 6 to 10, wherein the temperature coefficient of the coercive force Hc of the ferrite powder for a bonded magnet is 0.1% / ° C or less. A bonded magnet, comprising: the ferrite powder for a bonded magnet according to any one of claims 6 to 11; and a binder.

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