Method for producing iron-based oxide magnetic particle powder

Patent metadata

Field	Value
Publication number	US-2018208479-A1
Application number	US-201615746459-A
Country	US
Kind code	A1
Filing date	Jul 26, 2016
Priority date	Jul 27, 2015
Publication date	Jul 26, 2018
Grant date	—

Abstract

To provide iron-based oxide magnetic particle powder that has a narrow particle size distribution and a small content of fine particles that do not contribute to the magnetic recording characteristics, which result in a narrow coercive force distribution, and is suitable for the enhancement of the recording density of the magnetic recording medium, and a method for producing the same. An alkali is added to an aqueous solution containing a trivalent iron ion and an ion of the metal substituting a part of Fe sites to neutralize the aqueous solution to pH of 1.0 or more and 3.0 or less; a hydroxycarboxylic acid D is added in an amount providing a molar ratio D/Fe with respect to the amount of the trivalent iron ion or a molar ratio (D/(Fe+M)) with respect to the total amount of the trivalent iron ion and the ion of the metal M in the case where the substituting metal ion is contained of 0.125 or more and 1.0 or less; an alkali is further added to neutralize to pH of 7.0 or more and 10.0 or less; and then the iron oxyhydroxide containing the substituting metal element is coated with a silicon oxide and heated, so as to provide ε-type iron-based oxide magnetic particle powder containing the substituting metal element.

First claim

1 . A method for producing an iron-based oxide magnetic particle powder containing ε-Fe 2 O 3 , or ε-Fe 2 O 3 , a part of Fe sites of which is substituted by another metal element M, having an average particle diameter measured with a transmission electron microscope of 10 nm or more and 30 nm or less, the iron-based oxide magnetic particle powder having a value of I L /I H according to the following definition of 0.7 or less, and a value of α s /ε s according to the following definition of 0.5 or less,
the method comprising:
a first neutralizing step of neutralizing an aqueous solution containing a trivalent iron ion, or containing a trivalent iron ion and an ion of the metal M substituting a part of Fe sites to pH of 1.0 or more and 3.0 or less;
a step of adding a hydroxycarboxylic acid D to the aqueous solution after the neutralization in an amount providing a molar ratio D/Fe with respect to the amount of the trivalent iron ion in the case where the substituting metal ion is not contained, or a molar ratio D/(Fe+M) with respect to the total amount of the trivalent iron ion and the ion of the metal M in the case where the substituting metal ion is contained of 0.125 or more and 1.0 or less;
a second neutralizing step of neutralizing the aqueous solution having the hydroxycarboxylic acid added thereto, to pH of 7.0 or more and 10.0 or less;
a step of coating a silicon oxide on iron oxyhydroxide or iron oxyhydroxide containing the substituting metal element formed in the second neutralizing step; and
a step of heating the iron oxyhydroxide or the iron oxyhydroxide containing the substituting metal element coated with a silicon oxide, so as to provide iron oxide or iron oxide containing the substituting metal element coated with a silicon oxide,
wherein I H represents an intensity of a peak present on a high magnetic field side in a differential B-H curve obtained by numerical differentiation of a B-H curve obtained by measuring under conditions of an applied magnetic field of 1,035 kA/m (13 kOe), an M measurement range of 0.005 A·m 2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec, and I L represents an intensity of an intercept of an ordinate at zero magnetic field in the differential B-H curve, and
α s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 27.2° or more and 29.7° or less, and ε s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 42° or more and 44° or less.

2 . The method for producing an iron-based oxide magnetic particle powder according to claim 1 , wherein the first neutralizing step to the second neutralizing step are performed at a temperature retained at 60° C. or less.

3 . A method for producing an iron-based oxide magnetic particle powder containing ε-Fe 2 O 3 , or ε-Fe 2 O 3 , a part of Fe sites of which is substituted by another metal element M, having an average particle diameter measured with a transmission electron microscope of 10 nm or more and 30 nm or less, the iron-based oxide magnetic particle powder having a value of I L /I H according to the following definition of 0.7 or less, and a value of α s /ε s according to the following definition of 0.1 or less,
the method comprising:
a first neutralizing step of neutralizing an aqueous solution containing a trivalent iron ion, or containing a trivalent iron ion and an ion of the metal M substituting a part of Fe sites to pH of 1.0 or more and 3.0 or less at a temperature retained at 5° C. or more and 25° C. or less;
a step of adding a hydroxycarboxylic acid D to the aqueous solution after the neutralization at a temperature retained at 5° C. or more and 25° C. or less in an amount providing a molar ratio D/Fe with respect to the amount of the trivalent iron ion in the case where the substituting metal ion is not contained, or a molar ratio D/(Fe+M) with respect to the total amount of the trivalent iron ion and the ion of the metal M in the case where the substituting metal ion is contained of 0.125 or more and 1.0 or less;
a second neutralizing step of neutralizing the aqueous solution having the hydroxycarboxylic acid added thereto, to pH of 7.0 or more and 10.0 or less at a temperature retained at 5° C. or more and 25° C. or less;
a step of coating a silicon oxide on iron oxyhydroxide or iron oxyhydroxide containing the substituting metal element formed in the second neutralizing step; and
a step of heating the iron oxyhydroxide or the iron oxyhydroxide containing the substituting metal element coated with a silicon oxide, so as to provide iron oxide or iron oxide containing the substituting metal element coated with a silicon oxide,
wherein I H represents an intensity of a peak present on a high magnetic field side in a differential B-H curve obtained by numerical differentiation of a B-H curve obtained by measuring under conditions of an applied magnetic field of 1,035 kA/m (13 kOe), an M measurement range of 0.005 A·m 2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec, and I L represents an intensity of an intercept of an ordinate at zero magnetic field in the differential B-H curve, and
α s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 27.2° or more and 29.7° or less, and ε s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 42° or more and 44° or less.

4 . The method for producing an iron-based oxide magnetic particle powder according to claim 1 , wherein the method further comprises a step of removing the silicon oxide coated on the iron oxide or the iron oxide containing the substituting metal element.

5 . The method for producing an iron-based oxide magnetic particle powder according to claim 3 , wherein the method further comprises a step of removing the silicon oxide coated on the iron oxide or the iron oxide containing the substituting metal element.

6 . The method for producing iron-based oxide magnetic particle powder according to claim 1 , wherein the iron-based oxide is ε-A x B y C z Fe 2-x-y-z O 3 (wherein A represents at least one divalent metal element selected from Co, Ni, Mn, and Zn; B represents at least one tetravalent metal atom selected from Ti and Sn; C represents at least one trivalent metal element selected from In, Ga, and Al; and 0≤x, y, z<1).

7 . The method for producing iron-based oxide magnetic particle powder according to claim 1 , wherein the hydroxycarboxylic acid D is one or more selected from tartaric acid, citric acid, and malic acid.

Assignees

• Dowa Electronics Materials Co Ltd

Inventors

• Sakane Kenji
• Kawahito Tetsuya

Classifications

• C01P2004/04

  obtained by TEM, STEM, STM or AFM · CPC title

• H01F1/11

  in the form of particles {(for magnetic record carriers G11B5/70626)} · CPC title

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title

• C01P2002/52

  containing elements as dopants · CPC title

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title