CN111533550A - 铁氧体烧结磁铁 - Google Patents

铁氧体烧结磁铁 Download PDF

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CN111533550A
CN111533550A CN201911353366.6A CN201911353366A CN111533550A CN 111533550 A CN111533550 A CN 111533550A CN 201911353366 A CN201911353366 A CN 201911353366A CN 111533550 A CN111533550 A CN 111533550A
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ferrite
sintered magnet
ferrite sintered
less
raw material
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池田真规
森田启之
村川喜堂
室屋尚吾
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TDK Corp
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TDK Corp
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Abstract

该铁氧体烧结磁铁以下述式(1)所示的原子比含有金属元素，Ca1‑w‑xRwSrxFezCom···(1)，式(1)中，R为选自稀土元素和Bi中的至少一种元素，R至少包含La，式(1)中，w、x、z和m满足下述式(2)～(5)：0.360≤w≤0.420···(2)；0.110≤x≤0.173···(3)；8.51≤z≤9.71···(4)；0.208≤m≤0.269···(5)，在与易磁化轴平行的截面中，将总铁氧体晶粒的数量设为N、将具有层叠缺陷的铁氧体晶粒的数量设为n时，满足0≤n/N≤0.20。

Description

铁氧体烧结磁铁
技术领域
本发明涉及铁氧体烧结磁铁。
背景技术
作为由氧化物构成的永磁体的材料，已知有六方晶系的M型(磁铅石(magnetoplumbite)型)Sr铁氧体或Ba铁氧体。包含这些铁氧体的铁氧体磁铁以铁氧体烧结磁铁或粘结磁铁的形态作为永磁体被提供。近年来，随着电子部件的小型化、高性能化，对于铁氧体磁铁也要求具有小型且较高的磁特性。
作为永磁体的磁特性的指标，一般使用剩余磁通密度(Br)和矫顽力(HcJ)，被评价为这些指标越高而具有越高的磁特性。目前，从提高永磁体的Br和HcJ的观点来看，使铁氧体磁铁含有预定的元素等来改变组成而进行研究。
例如，在专利文献1中记载了添加有各种元素的六方晶系的铁氧体烧结磁铁。
现有技术文献
专利文献1：WO2011/004791号公报
发明内容
如上所述，进行了各种改变所添加的元素的组合的尝试，但哪种添加元素的组合赋予较高的矫顽力还未知。特别是如La的稀土元素和Co的组合等那样，添加价数和离子半径相互显著不同的元素的组合的情况下，有时矫顽力不充分。
本发明是鉴于上述状况而完成的发明，其目的在于：提供矫顽力优异的铁氧体磁铁。
本发明提供一种铁氧体烧结磁铁，其包含具有六方晶结构的铁氧体晶粒。该铁氧体烧结磁铁以下述式(1)所示的原子比含有金属元素。
Ca1-w-xRwSrxFezCom···(1)
式(1)中，R为选自稀土元素和Bi中的至少一种元素，R至少包含La，
式(1)中，w、x、z和m满足下述式(2)～(5)：
0.360≤w≤0.420···(2)；
0.110≤x≤0.173···(3)；
8.51≤z≤9.71···(4)；
0.208≤m≤0.269···(5)。
另外，在与易磁化轴平行的截面中，将总铁氧体晶粒的数量设为N、将具有层叠缺陷的铁氧体晶粒的数量设为n时，满足0≤n/N≤0.20。
该磁铁的矫顽力特别优异。
所述铁氧体烧结磁铁还可以含有以Al2O3换算计为0.03～0.3质量％的Al。铁氧体烧结磁铁通过在上述范围内含有Al，能够进一步提高HcJ。
上述铁氧体烧结磁铁可以含有以H3BO3换算计为0.037～0.181质量％的B。
由此，通过抑制烧结体的粒生长，并减小一次粒径，具有更加提高Hcj的效果。另外，通过含有B的晶界相均质地形成，能够抑制铁氧体晶粒间的磁相互作用，能够抑制Hcj的降低。
根据本发明，能够提供矫顽力优异的铁氧体烧结磁铁。
附图说明
图1为本发明实施方式涉及的铁氧体磁铁的与易磁化轴平行的截面的示意图，易磁化轴为图的垂直方向A；
图2为实施例2的铁氧体烧结磁铁的与易磁化轴方向平行的截面的TEM照片，易磁化轴为图的方向A。
附图标记说明
G…铁氧体晶粒、SF…线状区域。
具体实施方式
以下对本发明的优选实施方式进行说明。但是，本发明不限定于以下的实施方式。
(铁氧体烧结磁铁)
本实施方式涉及的铁氧体烧结磁铁包含具有六方晶结构的铁氧体晶粒。作为上述铁氧体，优选为磁铅石型铁氧体(M型铁氧体)。
本实施方式涉及的铁氧体烧结磁铁是以下述式(1)所示的原子比含有金属元素的氧化物。
Ca1-w-xRwSrxFezCom···(1)
式(1)中，R是选自稀土元素(包含Y)和Bi中的至少一种元素，R至少包含La。
另外，式(1)中，w、x、z和m满足下述式(2)～(5)。通过w、x、z和m满足下述式(2)～(5)，铁氧体烧结磁铁能够具有稳定且优异的剩余磁通密度Br和矫顽力HcJ。
0.360≤w≤0.420···(2)
0.110≤x≤0.173···(3)
8.51≤z≤9.71···(4)
0.208≤m≤0.269···(5)
本实施方式涉及的铁氧体烧结磁铁中的金属元素的原子比中的Ca的系数(1-w-x)优选超过0.435且低于0.500。当Ca的系数(1-w-x)超过0.435时，容易将铁氧体制成M型铁氧体。另外，除了减少α-Fe2O3等的非磁性相的比例之外，还具有抑制R过量而生成正铁氧体等的非磁性的异相，且能够抑制磁特性(特别是Br或HcJ)的降低的倾向。从同样的观点来看，更优选Ca的系数(1-w-x)为0.436以上，进一步优选超过0.445。另一方面，当Ca的系数(1-w-x)低于0.500时，容易将铁氧体制成M型铁氧体，除此之外，还能够减少CaFeO3-x等的非磁性相，能够容易得到优异的磁特性。从同样的观点来看，更优选Ca的系数(1-w-x)为0.491以下。
本实施方式涉及的铁氧体烧结磁铁中的金属元素的原子比中的R为选自稀土元素和Bi中的至少一种元素，至少包含La。作为稀土元素，可以列举La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu以及Y。R优选为La。R为La时，能够提高各向异性磁场。
本实施方式涉及的铁氧体烧结磁铁中的金属元素的原子比中的R的系数(w)为0.360以上、0.420以下。通过R的系数(w)处于上述范围内，能够得到良好的Br、HcJ和矩形比Hk/HcJ。当R的系数(w)成为0.360以上时，铁氧体烧结磁铁中的Co的固溶量变得充分，能够抑制Br和HcJ的降低。从同样的观点来看，优选R的系数(w)超过0.370，更优选为0.380以上。另一方面，R的系数(w)为0.420以下时，能够抑制生成正铁氧体等的非磁性的异相，能够将铁氧体烧结磁铁制成HcJ高的实用的磁铁。从同样的观点来看，优选R的系数(w)低于0.410。
本实施方式涉及的铁氧体烧结磁铁中的金属元素的原子比中的Sr的系数(x)为0.110以上、0.173以下。通过Sr的系数(x)处于上述范围内，能够得到良好的Br、HcJ以及Hk/HcJ。Sr的系数(x)成为0.110以上时，Ca和/或La的比率变小，能够抑制HcJ降低。另一方面，Sr的系数(x)为0.173以下时，能够容易得到充分的Br和HcJ。从同样的观点来看，Sr的系数(x)优选低于0.170，更优选低于0.165。
本实施方式涉及的铁氧体烧结磁铁中的金属元素的原子比中的Fe的系数(z)为8.51以上、9.71以下。通过Fe的系数(z)处于上述范围内，能够得到良好的Br、HcJ以及Hk/HcJ。从得到更良好的HcJ的观点来看，Fe的系数(z)优选超过8.70且低于9.40。另外，从得到更良好的Hk/HcJ的观点来看，Fe的系数(z)优选超过8.90且低于9.20。
本实施方式涉及的铁氧体烧结磁铁中的金属元素的原子比中的Co的系数(m)为0.208以上、0.269以下。Co的系数(m)成为0.208以上时，能够得到更优异的HcJ。从同样的观点来看，Co的系数(m)优选超过0.210，更优选超过0.220，进一步优选超过0.250以上。另一方面，Co的系数(m)为0.269以下时，能够得到更优异的Br。从同样的观点来看，Co的系数(m)优选为0.250以下。另外，通过铁氧体烧结磁铁含有Co，能够提高各向异性磁场。
本实施方式涉及的铁氧体烧结磁铁还可以含有Al(铝)。优选铁氧体烧结磁铁中的Al的含量以Al2O3换算计为0.03质量％以上、0.3质量％以下。铁氧体烧结磁铁含有以Al2O3换算计为0.03质量％以上的Al，由此，抑制预烧时的粒生长，所得到的铁氧体烧结磁铁的矫顽力进一步提高。另一方面，通过将铁氧体烧结磁铁中的Al的含量以Al2O3换算设为0.3质量％以下，能够得到优异的Br和HcJ。
本实施方式涉及的铁氧体烧结磁铁能够含有B(硼)。铁氧体烧结磁铁中的B的优选含量以H3BO3换算计为0.037质量％以上、0.181质量％以下。铁氧体烧结磁铁含有以H3BO3换算计为0.037质量％以上的B，由此，能够降低HcJ对预烧温度的依赖。从同样的观点来看，优选B的含量以H3BO3换算计为0.050质量％以上，更优选为0.070质量％以上。另一方面，通过将铁氧体烧结磁铁中的B的含量以H3BO3换算设为0.181质量％以下，能够维持较高的HcJ。从同样的观点来看，优选B的含量以H3BO3换算计为0.165质量％以下，更优选为0.150质量％以下。
本实施方式涉及的铁氧体烧结磁铁还可以含有Si(硅)。铁氧体烧结磁铁中的Si的含量以SiO2换算计可以为0.1～3质量％。通过铁氧体烧结磁铁在上述范围内含有Si，容易得到较高的HcJ。从同样的观点来看，Si的含量以SiO2换算计也可以为0.5～1.0质量％。
本实施方式涉及的铁氧体烧结磁铁还可以含有Ba(钡)。在铁氧体烧结磁铁含有Ba的情况下，铁氧体烧结磁铁中的Ba的含量能够以BaO换算计为0.001～0.068质量％。即使铁氧体烧结磁铁在上述范围内含有Ba，也能够以较高的值维持铁氧体烧结磁铁的HcJ。但是，当以BaO换算计含有超过0.068质量％的Ba时，具有烧制温度依赖性降低且矫顽力也降低的倾向。
本实施方式涉及的铁氧体烧结磁铁还可以含有Cr、Ga、Mg、Cu、Mn、Ni、Zn、In、Li、Ti、Zr、Ge、Sn、V、Nb、Ta、Sb、As、W和Mo等。各元素的含量以氧化物换算计优选为3质量％以下，进一步优选为1质量％以下。另外，从避免磁特性降低的观点来看，这些元素的合计含量也可以设为2质量％以下。
本实施方式涉及的铁氧体烧结磁铁优选不含碱金属元素(Na、K、Rb等)。碱金属元素具有容易降低铁氧体烧结磁铁的饱和磁化的倾向。但是，碱金属元素也有时包含在例如用于得到铁氧体烧结磁铁的原料中，如果是这样不可避免地包含的程度，则也可以包含于铁氧体烧结磁铁中。不显著影响磁特性的碱金属元素的含量为3质量％以下。
铁氧体烧结磁铁的组成能够通过荧光X射线定量分析测定。另外，主相的存在能够通过X射线衍射或电子射线衍射而确认。
本实施方式涉及的铁氧体烧结磁铁中的铁氧体晶粒的平均结晶粒径优选为1.5μm以下，更优选为1.0μm以下，进一步优选为0.5～1.0μm。通过具有这种平均结晶粒径，容易得到较高的HcJ。铁氧体烧结磁铁的结晶粒径能够通过SEM或TEM测定。
本实施方式涉及的铁氧体烧结磁铁在与易磁化轴平行的截面中，将总铁氧体晶粒的数量设为N、将具有层叠缺陷的铁氧体晶粒的数量设为n时，满足0≤n/N≤0.20。这种磁铁的矫顽力特别优异。以下有时将n/N称为层叠缺陷比例。n/N优选为0.15以下，更优选为0.07以下。
n和N能够设为例如包含50～100个左右的铁氧体晶粒的TEM照片中的值。图1是与易磁化轴A平行的截面的TEM照片的示意图。铁氧体晶粒G的c轴实际上与易磁化轴A的方向平行。
优选像铁氧体晶粒G’那样仅其一部分出现于照片的铁氧体晶粒不计算在N中，而计算像铁氧体晶粒G那样全部出现于照片的铁氧体晶粒的个数。即，N能够设为与易磁化轴A平行的截面TEM照片内的全部出现的铁氧体晶粒G的数量。另一方面，n是上述的铁氧体晶粒G中、晶粒内具有直线状的明区域或暗区域的晶粒的数量。以下，将直线状的明区域或暗区域称为线状区域SF。线状区域SF的长度可以为0.1μm以上，通常，将铁氧体晶粒的大小设为上限，不延伸到铁氧体晶粒之外。通常，线状区域SF与易磁化轴A垂直或相对易磁化轴A呈45°以上的角度地倾斜。有时一个铁氧体晶粒G中包含多个线状区域SF。线状区域SF与结晶中的层叠缺陷对应。
通过本实施方式涉及的铁氧体烧结磁铁满足上述的n/N的条件而矫顽力提高的原因虽然不清楚，但发明人认为以下。
磁铅石结构这样的六方晶铁氧体的氧离子如ABAB····那样层叠并六方最密充填。层叠缺陷是该ABAB···那样的层叠的顺序混乱的面缺陷。当存在层叠缺陷时，一个铁氧体晶粒被磁分割，因此认为反磁场系数增加，矫顽力降低。认为通过将层叠缺陷比例设为0～0.19，能够得到较高的特性。
(铁氧体烧结磁铁的制造方法)
以下表示本实施方式涉及的铁氧体烧结磁铁的制造方法的一例。上述制造方法包括原料粉末制备工序、预烧工序、粉碎工序、成型工序以及烧制工序。另外，上述制造方法也可以在上述粉碎工序与上述成型工序之间包括微粉碎浆料的干燥工序和混炼工序，也可以在上述成型工序与上述烧制工序之间包括脱脂工序。以下说明各工序。
＜原料粉末制备工序＞
在原料粉末制备工序中，将铁氧体烧结磁铁的原料混合，得到原料混合物，根据需要，对其进行粉碎，由此得到原料粉末。首先，作为铁氧体烧结磁铁的原料，可以举出含有构成其的元素中的1种或2种以上的化合物(原料化合物)。原料化合物例如优选为粉末状的化合物。作为原料化合物，可以举出各元素的氧化物或通过烧制而形成氧化物的化合物(碳酸盐、氢氧化物、硝酸盐等)。例如，可以例示：SrCO3、La2O3、Fe2O3、BaCO3、CaCO3、Co3O4、H3BO3、Al2O3和SiO2等。
Fe化合物的平均一次粒径优选为0.5μm以下，更优选为0.4μm以下，进一步优选为0.3μm以下。
Sr化合物的平均一次粒径优选为2.0μm以下，更优选为1.0μm以下，进一步优选为0.5μm以下。
Ca化合物的平均一次粒径优选为1.0μm以下，更优选为0.3μm以下。
其它的原料颗粒的平均一次粒径优选为2μm以下。
平均一次粒径可以设为利用激光衍射式粒度分布装置得到的体积基准的粒度分布的D50。
通过使用微细且粒径一致的原料颗粒，能够使预烧体的一次粒径均匀。其结果，能够减少层叠缺陷的比例。
以能够得到例如所期望的铁氧体烧结磁铁的组成的量，称量各原料，并混合之后，使用湿式磨碎机、球磨机等，进行0.1～20小时左右的混合、粉碎。原料化合物的粉末的平均粒径从例如能够均匀配合的观点来看，优选设为0.1～5.0μm左右。原料粉末至少含有Ca、R、Sr、Fe、Co和B。特别是通过原料粉末含有B，能够进一步降低铁氧体烧结磁铁的磁特性对预烧温度的依赖性。另外，在铁氧体烧结磁铁含有Al的情况下，原料粉末还含有Al。由此，能够抑制预烧中的粒生长，并能够减小预烧体的一次粒径。
原料的一部分也能够在后述的粉碎工序添加。但是，在本实施方式中，优选在粉碎工序中不添加原料的一部分。即，优选构成得到的铁氧体烧结磁铁的Ca、R、Sr、Fe、Co和B的全部(除不可避免地混入的元素之外)由原料粉末制备工序中的原料粉末供给。特别优选构成铁氧体烧结磁铁的B的全部由原料粉末制备工序中的原料粉末供给。另外，优选构成铁氧体烧结磁铁的Al的全部由原料粉末制备工序中的原料粉末供给。由此，更容易得到原料粉末含有B或Al产生的上述的效果。
＜预烧工序＞
在预烧工序中，将原料粉末制备工序中得到的原料粉末进行预烧。预烧优选在例如空气(大气)中等的氧化性氛围中进行。预烧的温度优选为1100～1400℃的温度范围，更优选为1100～1300℃，进一步优选为1150～1300℃。在本实施方式涉及的铁氧体烧结磁铁的制造方法中，在上述预烧温度的任意温度下都能够得到稳定的磁特性。预烧的时间(以预烧的温度保持的时间)可以为1秒～10小时，优选为1秒～5小时。通过预烧得到的预烧体含有70％以上的上述那样的主相(M相)。预烧体的一次粒径优选为5μm以下，更优选为2μm以下，进一步优选为1μm以下。通过抑制预烧中的粒生长，并减小预烧体的一次粒径(例如1μm以下)，能够进一步提高所得到的铁氧体烧结磁铁的HcJ。
＜粉碎工序＞
在粉碎工序中，将预烧工序中成为颗粒状或块状的预烧体粉碎，再制成粉末状。由此，后述的成型工序中的成型变得容易。在该粉碎工序中，也可以进一步添加在原料粉末制备工序中未混合的原料。但是，从得到预烧温度依赖性的效果或预烧中的粒生长的抑制效果的观点来看，优选原料在原料粉末制备工序中全部混合。粉碎工序也可以包括以例如使预烧体成为粗粉末的方式进行粉碎(粗粉碎)后，将其进一步微细地粉碎(微粉碎)的两个阶段的工序。
粗粉碎使用例如振动磨机等进行至平均粒径成为0.5～5.0μm。微粉碎中，将粗粉碎中得到的粗粉碎材料进一步利用湿式磨碎机、球磨机或喷射磨等进行粉碎。在微粉碎中，以得到的微粉碎材料的平均粒径优选成为0.08～2.0μm、更优选成为0.1～1.0μm、进一步优选成为0.1～0.5μm左右的方式，进行微粉碎。微粉碎材料的比表面积(例如，通过BET法求得。)优选为4～12m2/g左右。优选的粉碎时间根据粉碎方法不同而不同，在例如湿式磨碎机的情况下，优选为30分钟～20小时左右，利用球磨机的湿式粉碎中，优选为10～50小时左右。
在微粉碎工序中，在湿式法的情况下，作为分散介质，除了水之外，还可以使用甲苯和二甲苯等非水系分散介质。在使用非水系分散介质的情况下，具有在后述的湿式成型时能够得到高取向性的倾向。另一方面，在使用水系分散介质的情况下，从生产力的观点来看是有利的。
另外，在微粉碎工序中，为了提高烧制后所得到的烧结体的取向度，例如，作为分散剂，也可以添加通式Cn(OH)nHn+2所示的多元醇。在此，作为多元醇，通式中，n优选为4～100，更优选为4～30，进一步优选为4～20，特别优选为4～12。作为多元醇，例如可以举出山梨糖醇。另外，也可以并用两种以上的多元醇。另外，除了多元醇之外，还可以并用其它公知的分散剂。
在添加多元醇的情况下，其添加量相对于添加对象物(例如，粗粉碎材料)优选为0.05～5.0质量％，更优选为0.1～3.0质量％，进一步优选为0.2～2.0质量％。此外，在微粉碎工序中所添加的多元醇在后述的烧制工序中进行热分解除去。
＜成型工序＞
在成型工序中，将粉碎工序后所得到的粉碎材料(优选为微粉碎材料)在磁场中成型，得到成型体。成型通过干式成型和湿式成型的任意方法均能够进行。从提高磁取向度的观点来看，优选通过湿式成型进行。
在通过湿式成型进行成型的情况下，优选例如通过以湿式进行上述的微粉碎工序而得到浆料后，将该浆料浓缩成规定的浓度，得到湿式成型用浆料，使用其进行成型。浆料的浓缩能够通过离心分离或压滤等进行。湿式成型用浆料优选在其总量中、微粉碎材料占30～80质量％左右。在该情况下，也可以向浆料中添加葡萄糖酸、葡萄糖酸盐以及山梨糖醇等表面活性剂。另外，作为分散介质，也可以使用非水系分散介质。作为非水系分散介质，能够使用甲苯和二甲苯等有机分散介质。在该情况下，优选添加油酸等表面活性剂。此外，湿式成型用浆料也可以通过向微粉碎后的干燥状态的微粉碎材料中添加分散介质等而制备。
在湿式成型中，接着对该湿式成型用浆料进行磁场中成型。在该情况下，成型压力优选为9.8～49MPa(0.1～0.5ton/cm2)左右，施加的磁场优选设为398～1194kA/m(5～15kOe)左右。
＜烧制工序＞
在烧制工序中，将成型工序中得到的成型体烧制而设为烧结体。由此，能够得到上述那样的铁氧体磁铁的烧结体即铁氧体烧结磁铁。烧制能够在大气中等氧化性氛围中进行。烧制温度优选为1120～1270℃，更优选为1150～1240℃。另外，烧制时间(烧制温度下的保持时间)优选为0.5～3小时左右。
在利用上述那样的湿式成型得到成型体的情况下，在未使该成型体充分干燥的状态下，在烧制工序中急剧地加热时，分散介质等的挥发剧烈地产生，可能在成型体上产生裂纹。因此，从避免这种不良情况的观点来看，优选在达到上述的烧制温度之前，例如以1℃/分钟左右的低升温速度从室温加热到100℃左右，使成型体充分干燥，由此抑制裂纹的产生。另外，在添加表面活性剂(分散剂)等的情况下，优选在例如100～500℃左右的温度范围，以3℃/分钟左右的升温速度进行加热，由此将它们充分除去(脱脂处理)。此外，这些处理也可以在烧制工序的开始进行，也可以在烧制工序之前另外进行。
另外，从1100℃到烧制温度的升温速度优选为4℃/分钟以下，更优选为3℃/分钟以下，进一步优选为1℃/分钟以下。另一方面，从烧制温度到1100℃的降温速度优选为6℃/分钟以上，更优选为10℃/分钟以上。通过在1100℃以上的升温速度和直到1100℃的降温速度处于上述范围内，容易降低层叠缺陷比例。
以上，对铁氧体烧结磁铁的优选制造方法进行说明，但只要制造本发明的铁氧体烧结磁铁，其制造方法就不限定于上述中说明的制造方法，条件等能够适当变更。
铁氧体烧结磁铁的形状没有特别限定。铁氧体烧结磁铁也可以是圆盘那样的板状，也可以是圆柱或四棱柱那样的柱状，也可以是C形、弓形和拱门形状等形状，也可以是环形状。
本实施方式涉及的铁氧体烧结磁铁能够用于例如电动机和发电机等的旋转机以及各种传感器等。
实施例
以下，通过实施例更详细地说明本发明，但本发明不限定于以下的实施例。
(铁氧体烧结磁铁的制作)
[实施例1]
＜原料粉末制备工序＞
作为构成铁氧体烧结磁铁的金属元素的原料，准备平均一次粒径0.3μm的碳酸钙(CaCO3)颗粒、氧化镧(La2O3)颗粒、平均一次粒径0.5μm的碳酸锶(SrCO3)颗粒、平均一次粒径0.3μm的氧化铁(Fe2O3：作为杂质，包含Mn、Cr、Al、Si和Cl)、以及氧化钴(Co3O4)颗粒。以下述式(1a)所示的原子比含有金属元素的铁氧体烧结磁铁中、大致成为w＝0.388、x＝0.133、z＝8.721、m＝0.247的量称量上述原料并混合。接着，作为铁氧体烧结磁铁的原料，进一步准备硼酸(H3BO3)颗粒和氧化铝(Al2O3)颗粒。以相对于得到的铁氧体烧结磁铁整体、硼的含量以H3BO3换算计为0.144质量％、铝的含量以Al2O3换算计为0.060质量％的量，分别称量硼酸颗粒和氧化铝颗粒，并添加至上述混合物中。将得到的原料混合物利用湿式磨碎机混合、粉碎、干燥，得到原料粉末。
Ca1-w-xLawSrxFezCom···(1a)
＜预烧和粉碎工序＞
相对于原料粉末，在大气中进行以1200℃保持2小时的预烧，得到预烧体。将得到的预烧体以通过BET法求得的比表面积成为0.5～2.5m2/g的方式，利用小型棒振动磨机进行粗粉碎。将得到的粗粉碎材料使用湿式球磨机微粉碎32小时，得到具有通过BET法求得的比表面积为7.0～10m2/g的微粉碎颗粒的湿式成型用浆料。将微粉碎后的浆料利用离心分离机脱水，将固体成分浓度调整成70～80质量％，由此得到湿式成型用浆料。
＜成型和烧制工序＞
将湿式成型用浆料使用湿式磁场成型机，在10kOe的施加磁场中成型，得到直径30mm×厚度15mm的圆柱状的成型体。将得到的成型体在大气中以室温充分干燥。接着，在大气中升温，特别是在1100℃以上以1.0℃/分钟升温，并以1205℃保持1小时，然后以10.0℃/分钟降温至1100℃，然后进行降温至室温的烧制，得到实施例1的铁氧体烧结磁铁。
[实施例2]
在原料粉末制备工序中，使用平均一次粒径为0.4μm的Fe2O3颗粒代替平均一次粒径为0.3μm的Fe2O3颗粒，使用平均一次粒径为1.0μm的SrCO3颗粒代替平均一次粒径为0.5μm的SrCO3颗粒，除此以外，与实施例1相同，得到实施例2的铁氧体烧结磁铁。
[实施例3]
在原料粉末制备工序中，使用平均一次粒径为0.5μm的Fe2O3颗粒代替平均一次粒径为0.3μm的Fe2O3颗粒，使用平均一次粒径为2.0μm的SrCO3颗粒代替平均一次粒径为0.5μm的SrCO3颗粒，使用平均一次粒径为1.0μm的CaCO3颗粒代替平均一次粒径为0.3μm的CaCO3颗粒，除此以外，与实施例2相同，得到实施例3的铁氧体烧结磁铁。
[比较例1]
在烧制工序中，设为在1100℃以上的升温速度5.0℃/分钟，将烧制温度设为1220℃，将直到1100℃的降温速度设为5.0℃/分钟，除此以外，与实施例3相同，得到比较例1的铁氧体烧结磁铁。
(评价方法)
[层叠缺陷比例]
拍摄各实施例的磁铁的与易磁化轴平行的截面的TEM照片。图像的范围设为：纵为4μm，横为7.4μm，将纵向设为易磁化轴。求得图像的范围内出现所有的区域的铁氧体晶粒的数量N之后，求得N中、在晶粒内具有线状区域的晶粒的数量n，并求得作为层叠缺陷比例的n/N。将实施例2中的TEM照片的例子表示在图2中。白箭头表示线状区域SF的一例。
[磁特性]
对实施例和比较例中得到的圆柱状的各铁氧体烧结磁铁的上下表面进行加工后，使用最大施加磁场25kOe的B-H示踪器，求得它们的剩余磁通密度Br(mT)和矫顽力HcJ(kA/m)，并且测定磁通密度成为Br的90％时的外部磁场强度(Hk)。根据Hk和HcJ的测定结果求得矩形比Hk/HcJ。
将产品的分析组成、制造条件、n/N和磁特性表示在表1中。
[表1]
Figure BDA0002335237930000141
在层叠缺陷比例n/N低的实施例中，与比较例相比，特别能够看到矫顽力的提高。

Claims (3)

1.一种铁氧体烧结磁铁，其特征在于：
包含具有六方晶结构的铁氧体晶粒，
所述铁氧体烧结磁铁以下述式(1)所示的原子比含有金属元素，
Ca1-w-xRwSrxFezCom···(1)
式(1)中，R为选自稀土元素和Bi中的至少一种元素，R至少包含La，
式(1)中，w、x、z和m满足下述式(2)～(5)：
0.360≤w≤0.420···(2)；
0.110≤x≤0.173···(3)；
8.51≤z≤9.71···(4)；
0.208≤m≤0.269···(5)，
在与易磁化轴平行的截面中，将总铁氧体晶粒的数量设为N、将具有层叠缺陷的铁氧体晶粒的数量设为n时，满足0≤n/N≤0.20。
2.如权利要求1所述的铁氧体烧结磁铁，其特征在于：
还含有以Al2O3换算计为0.03～0.3质量％的Al。
3.如权利要求1或2所述的铁氧体烧结磁铁，其特征在于：
还含有以H3BO3换算计为0.037～0.181质量％的B。
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