JP5521622B2 - Magnetic oxide material, sintered ferrite magnet, and method for producing sintered ferrite magnet - Google Patents

Description

  The present invention relates to an oxide magnetic material, a ferrite sintered magnet, and a method for producing a ferrite sintered magnet.

Ferrite sintered magnets are used in various applications such as various motors, generators, and speakers. As typical ferrite sintered magnets, Sr ferrite (SrFe ₁₂ O ₁₉ ) and Ba ferrite (BaFe ₁₂ O ₁₉ ) having a hexagonal M-type magnetoplumbite structure are known. For example, iron oxide and carbonates such as strontium (Sr) and barium (Ba) are used as raw materials and are manufactured at a relatively low cost by powder metallurgy.

In recent years, due to environmental considerations and the like, there has been a demand for improving the magnetic properties of sintered ferrite magnets for the purpose of reducing the size, weight, and efficiency of automotive electrical components and electrical equipment components. In particular, motors used in automotive electrical components have a high intrinsic magnetic flux that is not demagnetized by a demagnetizing field that is generated when the thickness is reduced while maintaining a high residual magnetic flux density B _r (hereinafter simply referred to as “B _r ”). There is a demand for a sintered ferrite magnet having a magnetic force H _cJ (hereinafter simply referred to as “H _cJ ”).

Order to improve the magnetic properties of the ferrite sintered magnet, a portion of Sr in said Sr ferrite substituted with a rare earth element such as La, by substituting a part of Fe with Co, the H _cJ and B _r A method for improving the above has been proposed in JP-A-10-149910 (Patent Document 1), JP-A-11-154604 (Patent Document 2), and the like.

  The Sr ferrite described in Patent Documents 1 and 2 in which a part of Sr is substituted with a rare earth element such as La and a part of Fe is substituted with Co or the like (hereinafter referred to as “SrLaCo ferrite”) has excellent magnet characteristics. Therefore, although it is used for various applications in place of the conventional Sr ferrite and Ba ferrite, further improvement in magnet characteristics is desired.

On the other hand, Ca ferrite is also known as a ferrite sintered magnet together with the Sr ferrite and Ba ferrite. Ca ferrite has a stable structure of CaO—Fe ₂ O ₃ or CaO—2Fe ₂ O ₃ and is known to form hexagonal ferrite by adding La. However, the magnet properties obtained are comparable to those of conventional Ba ferrite and are not sufficiently high.

Patent No. 3181559 (Patent Document 3), the improvement of B _r and H _cJ of the Ca ferrite, and for improving the temperature characteristics of the H _cJ, by replacing part of Ca with rare earth elements such as La, the Fe Ca ferrite partially substituted with Co (hereinafter referred to as “CaLaCo ferrite”) is disclosed. The anisotropic magnetic field H _A (hereinafter simply referred to as “H _A ”) of CaLaCo ferrite is smaller than that of Sr ferrite. It states that a value of 20 kOe or higher can be obtained, which is 10% higher than the maximum.

However, CaLaCo ferrite disclosed in Patent Document 3, although having properties which exceed H _A in SrLaCo ferrite, B _r and H _cJ are comparable to SrLaCo ferrite, while the squareness ratio H _k / H _cJ (hereinafter, (It is simply called “H _k / H _cJ ”) and it cannot satisfy both high H _cJ and high H _k / H _cJ and has not yet been applied to various applications such as motors. .

  In order to improve the magnetic properties of the CaLaCo ferrite, the following proposals have been made.

  Japanese Patent Laid-Open No. 2006-104050 (Patent Document 4) proposes to optimize the atomic ratio and molar ratio n of each constituent element and to contain La and Co at a specific ratio. International Publication No. 2007/060757 (Patent Document 5) proposes replacing a part of Ca with La and Ba. International Publication No. 2007/077811 (Patent Document 6) proposes replacing a part of Ca with La and Sr.

The invention described in Patent Document 4~6, CaLaCo ferrite sintered magnet having a high B _r and a high H _cJ than the SrLaCo ferrite is obtained. However, the ferrite sintered magnets described in Patent Documents 4 to 6 contain Co in an atomic ratio of about 0.3 in order to obtain high magnet properties, and are currently being marketed SrLaCo ferrite sintered magnets (atomic ratio) Therefore, there is a problem that the raw material cost is increased.

One of the biggest features of sintered ferrite magnets is high economy. Therefore, even a ferrite sintered magnet having high magnet properties is not accepted in the market if the price is high. For example, the price of Co and La is equivalent to 10 to several tens of times that of iron oxide, which is the main component, so the higher the content of Co and La, the higher the price of the sintered ferrite magnet (2009 November LMB (London Metal Bulletin) cobalt market price is 21.1-22.0 $ / lb for high-grade products, and is simply 3,100-3,200 yen / kg when converted to Co ₃ O ₄ ; Japan CIF La market price is 10 $ / kg It is about 770 yen / kg when simply converted to La ₂ O ₃ ).

  However, if the Ca content in CaLaCo ferrite is the same as that of SrLaCo ferrite (at an atomic ratio of about 0.2), the magnet characteristics are equivalent to SrLaCo ferrite and the characteristics of CaLaCo ferrite are lost.

Japanese Patent Laid-Open No. 2006-93196 (Patent Document 7) discloses a formula: A _1-x R _x (Fe _12-y (Co _1-m Me _m )) in order to reduce the cost of M-type ferrite containing La and Co. _y ) _z O ₁₉ (where A is at least one selected from Sr, Ba, Ca, and Pb, R is at least one selected from rare earth elements (including Y) and Bi, and must contain La) (Me is one or more of Zn, Ni, and Mg), and a ferrite in which a part of Co is substituted with an inexpensive metal element Me (at least one of Zn, Ni, and Mg) Proposes magnetic materials. Patent Document 7 describes that a decrease in H _cJ accompanying a reduction in Co amount can be suppressed by _setting the ratio of La to (Co + Me) in the range of _{1.1 to 1.8} .

In the method described in Patent Document 7, the raw material cost can be reduced by reducing the amount of Co. However, this ferrite magnetic material reduces H _cJ due to substitution of Co for Me, and increases the amount of R elements such as La ( x / yz is set to 1.1 to 1.8), and the magnet characteristics are not improved as compared with those not replaced by Me. Therefore, sufficiently satisfactory magnet characteristics are not obtained for the recent demand for higher performance.

Japanese Patent Laid-Open No. 10-149910 Japanese Patent Laid-Open No. 11-154604 Japanese Patent No. 3181559 JP 2006-104050 A International Publication No. 2007/060757 Pamphlet International Publication No. 2007/077811 Pamphlet Japanese Unexamined Patent Publication No. 2006-93196

An object of the present invention is to provide an oxide magnetic material and a ferrite sintered magnet having high H _cJ at a low cost, and in particular, in CaLaCo ferrite having excellent magnet characteristics, the raw material cost is reduced by reducing the Co content. with decreasing, while maintaining high B _r and a high H _k / H _cJ, improves H _cJ, to satisfy the recent demand for increasingly become stronger performance, demagnetization by the demagnetizing field generated when the thin It is to provide an oxide magnetic material and a ferrite sintered magnet having a high H _cJ .

In view of the above object, the inventors focused attention on the H _A of CaLaCo ferrite and SrLaCo ferrite. H _cJ of the sintered ferrite magnet is theoretically proportional to _HA . In other words, improvement in H _cJ as H _A material is high is expected. Inventors have found that by measuring the H _A of CaLaCo ferrite and SrLaCo ferrite 0.2 atomic proportion of Co are both from the magnetic hysteresis curve by SPD (Singular Point Detection) method, respectively 1.9 MA / m (about 23.9 kOe) and Since it is 1.8 MA / m (about 22.6 kOe), the CaLaCo ferrite sintered magnet has the same Co content as the SrLaCo ferrite sintered magnet currently offered to the market (at an atomic ratio of about 0.2), It is predicted that higher H _cJ than SrLaCo ferrite will be obtained. However, magnetic properties of the resulting CaLaCo ferrite sintered magnet becomes a same level as that of SrLaCo ferrite sintered magnets, high H _cJ as expected from the values of H _A was obtained.

Therefore, as a result of further intensive research aimed at improving the magnetic properties of CaLaCo ferrite with an atomic ratio of about 0.2 in terms of atomic ratio, particularly _HcJ , a part of Fe was replaced with a small amount of Mg, and the atomic ratio of Co and Mg by the sum of the specific range, it found that can improve the H _cJ of high B _r and a high H _k / H _cJ while maintaining the CaLaCo ferrite sintered magnet, and conceived the present invention.

As described above, Patent Document 7 describes that the cost can be reduced by substituting part of Co of M-type ferrite containing La and Co with Mg or the like. However, in Patent Document 7, the decrease in H _cJ due to substitution of Me is compensated by an increase in R elements such as La (rare earth elements and Bi), and the technical idea of improving H _cJ by including Mg is Absent.

  Although there is a description in Patent Document 7 that at least one of Sr, Ba, Ca, and Pb can be selected as the A element, what is described in the examples is the SrLaCo ferrite in which Sr is selected as the A element However, it is unclear whether the configuration of the invention according to Patent Document 7 can be adopted in BaLaCo ferrite or CaLaCo ferrite and the required effect can be obtained.

Of the present invention, a portion of Fe was replaced with Mg, by a specific range of total atomic ratio of Co and Mg, high B _r and a high H _k / H _cJ of CaLaCo ferrite sintered magnet while maintaining the The feature that _HcJ can be improved cannot be obtained with SrLaCo ferrite, as shown in Examples described later. That is, it can be said that the SrLaCo ferrite described in Patent Document 7 and the CaLaCo ferrite of the present invention are completely different ferrites.

The oxide magnetic material of the present invention has a composition ratio of R, which is at least one of Ca and rare earth elements and essentially contains La, A element which is Ba and / or Sr, Fe, Co and Mg metal elements. ,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y and y ′ representing the atomic ratio of R element, A element, Co and Mg, respectively, and n representing the molar ratio,
0.4 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.1 ≦ y ≦ 0.3,
0 <y '≦ 0.25,
0.25 ≦ y + y ′ ≦ 0.37, and
4 ≦ n ≦ 6
It is a numerical value that satisfies ).

  The x is preferably a numerical value satisfying 0.45 ≦ x ≦ 0.55.

  The x ′ is preferably a numerical value satisfying 0 <x ′ ≦ 0.15.

  X ′ is preferably a numerical value satisfying 0.03 ≦ x ′ ≦ 0.1.

  The y is preferably a numerical value satisfying 0.15 ≦ y ≦ 0.24.

  The y ′ is preferably a numerical value satisfying 0.05 ≦ y ′ ≦ 0.2.

  The y + y ′ is preferably a numerical value satisfying 0.27 ≦ y + y ′ ≦ 0.35.

  The n is preferably a numerical value satisfying 4.5 ≦ n ≦ 5.6.

The sintered ferrite magnet of the present invention includes a ferrite phase having a hexagonal M-type magnetoplumbite structure,
A ferrite sintered magnet having a grain boundary phase essentially containing Si,
The composition ratio of Ca, R element which is at least one of rare earth elements and essentially contains La, Ba element and / or Sr element A, Fe, Co and Mg metal elements,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio,
0.288 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.07 ≦ y ≦ 0.3,
0 <y '≦ 0.2,
0.18 ≦ y + y ′ ≦ 0.37, and
3.08 ≦ n ≦ 6
It is a numerical value that satisfies And 2% by mass or less of Si in terms of SiO _{2 in the} entire sintered ferrite magnet.

The method of the present invention for producing a sintered ferrite magnet includes at least one of Ca, a rare earth element, and an R element that essentially contains La, an A element that is Ba and / or Sr, a metallic element of Fe, Co, and Mg. The composition ratio of
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio,
0.4 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.1 ≦ y ≦ 0.3,
0 <y '≦ 0.25,
0.25 ≦ y + y ′ ≦ 0.37, and
4 ≦ n ≦ 6
It is a numerical value that satisfies ) And a step of preparing a ferrite calcined body containing a ferrite phase having a hexagonal M-type magnetoplumbite structure, the calcined body is 2 in terms of CaO with respect to 100% by mass of the calcined body. A step of adding CaCO ₃ of 2 mass% or less and SiO ₂ of 2 mass% or less, crushing the calcined body to which CaCO ₃ and SiO ₂ have been added, obtaining a powder, molding the powder, and molding And a firing step of firing the shaped body to obtain a sintered body.

Another method of the present invention for producing a sintered ferrite magnet has a ferrite phase having a hexagonal M-type magnetoplumbite structure and a grain boundary phase essentially containing Si, and contains at least one of Ca and a rare earth element. The composition ratio of the R element, which is a seed and essentially containing La, the A element which is Ba and / or Sr, the metal element of Fe, Co and Mg,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio,
0.288 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.07 ≦ y ≦ 0.3,
0 <y '≦ 0.2,
0.18 ≦ y + y ′ ≦ 0.37, and
3.08 ≦ n ≦ 6
It is a numerical value that satisfies ) And is a method for producing a ferrite sintered magnet containing 2 mass% or less of Si in terms of SiO ₂ out of the entire ferrite sintered magnet,
Preparing a ferrite calcined body,
The step of adding to the calcined body 100% by mass of the calcined body, 2% by mass or less of CaCO ₃ and 2% by mass or less of SiO ₂ in terms of CaO,
Crushing the calcined body to which CaCO ₃ and SiO ₂ have been added to obtain a powder;
The method includes a molding step of molding the powder to obtain a molded body, and a firing step of firing the molded body to obtain a sintered body.

The present invention, while maintaining high B _r and a high H _k / H _cJ, it is possible to improve the H _cJ, satisfy the requirements in recent years increasingly become stronger performance occurs when the thinned anti An oxide magnetic material and a sintered ferrite magnet having high H _cJ that are not demagnetized by a magnetic field can be provided.

It is possible to reduce the Co content than the CaLaCo ferrite disclosed in Patent Document 4 to 6 described above, while maintaining a high B _r and a high H _k / H _cJ, oxides with improved H _cJ Magnetic materials and sintered ferrite magnets can be provided at low cost.

  By substituting a part of Fe with Mg, the optimum range of n value (range in which high magnet characteristics can be obtained) is shifted to a larger side, and the content of Fe is relatively increased. Therefore, the content of expensive elements such as Co and La is reduced, the raw material cost is further reduced, and an inexpensive oxide magnetic material and ferrite sintered magnet can be provided.

  By using the oxide magnetic material and the sintered ferrite magnet of the present invention, it is possible to provide an electric component for an automobile and a component for an electric device which are reduced in size, weight and efficiency.

It is a graph showing the relationship between the atomic ratio of Mg ferrite sintered magnet of Example 1 and (y ') and B _r. 3 is a graph showing the relationship between the Mg atomic ratio (y ′) and H _cJ of the sintered ferrite magnet of Example 1. FIG. It is a graph showing the relationship between the total atomic ratio of Co and Mg ferrite sintered magnet of Example 1 and (y + y ') and B _r. 4 is a graph showing the relationship between the total of the atomic ratios of Co and Mg (y + y ′) of the sintered ferrite magnet of Example 1 and H _cJ . Is a graph showing the relationship between the La atom ratio of the ferrite sintered magnet of Example 2 (x) and B _r and H _cJ. Is a graph showing the relationship between the molar ratio n and B _r and H _cJ of the sintered ferrite magnets of Example 3. Is a graph showing the relationship between the atomic ratio of A element of the ferrite sintered magnet of Example 4 and (x ') and B _r and H _cJ. It is a graph showing the relationship between the atomic ratio of the ferrite sintered magnet Mg in Example 7 and (y ') and B _r and H _cJ.

[1] Oxide magnetic material The oxide magnetic material of the present invention is an element R, Ba and / or Sr, which is at least one of Ca and rare earth elements and contains La as essential, Fe, Co, and Mg. The composition ratio of the metal element is
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y and y ′ representing the atomic ratio of R element, A element, Co and Mg, respectively, and n representing the molar ratio are 0.4 ≦ x ≦ 0.6, 0 ≦ x ′ ≦ 0.2, 0.1 ≦ y ≦ 0.3, 0 <y ′ ≦ 0.25, 0.25 ≦ y + y ′ ≦ 0.37, and 4 ≦ n ≦ 6.

The atomic ratio of Ca (1-x-x ′) is 0.2 ≦ 1-x-x ′ ≦ 0.6 from the range of x and x ′. The atomic ratio of less than 0.2 of Ca, R element and the element A B _r and H _k / H _cJ is reduced because relatively increased.

The R element is at least one kind of rare earth element and contains La as an essential element. In order to impart high magnet properties, the ratio of La in the R element is preferably 50 atomic% or more, more preferably 70 atomic% or more, and La alone (however, inevitable impurities are allowed) ) Is most preferred. Of the R elements, La is most easily dissolved in the M phase. Therefore, the larger the ratio of La, the greater the effect of improving magnetic properties. The atomic ratio (x) of the R element is 0.4 ≦ x ≦ 0.6. x is B _r and H _k / H _cJ is reduced when it exceeds 0.4 and less than 0.6. A more preferable range is 0.45 ≦ x ≦ 0.55.

The element A is Ba and / or Sr. The atomic ratio (x ′) of the A element is 0 ≦ x ′ ≦ 0.2. Even if the element A is not contained, the effect of the present invention is not impaired. However, by adding the element A, the crystal in the calcined body is refined and the aspect ratio is reduced, so that _HcJ is further improved. A preferable range of x ′ is 0 <x ′ ≦ 0.15, and a more preferable range is 0.03 ≦ x ′ ≦ 0.1.

The atomic ratio (y) of Co is 0.1 ≦ y ≦ 0.3. In the CaLaCo ferrite sintered magnets described in Patent Documents 4 to 6, the optimum value of the Co atomic ratio is about 0.3, and when it is less than that, H _cJ is lowered, and the CaLaCo ferrite is superior in magnetic properties than SrLaCo. Features are lost. However, in the present invention, by substituting a part of Fe with Mg, it is possible to improve the H _cJ remains atomic ratio of Co is maintaining high B _r and a high H _k / H _cJ even 0.3 following areas it can. If the atomic ratio (y) of Co is less than 0.1, the effect of improving the magnet properties by adding Co cannot be obtained. On the other hand, even if y exceeds 0.3, the magnetic properties do not deteriorate, and with increasing y, _HcJ is further improved, but the raw material cost is increased. Therefore, in order to make H _cJ higher than that of a general SrLaCo ferrite and to make the raw material cost comparable to that of a general SrLaCo ferrite, y is set to 0.3 or less. A more preferable range is 0.15 ≦ y ≦ 0.24.

The atomic ratio (y ′) of Mg is 0 <y ′ ≦ 0.25. The feature of the present invention is that a part of Fe is replaced with Mg. When y ′ is 0, the effect of improving _HcJ and the effect of reducing raw material costs due to the reduction of Co cannot be obtained. Conversely, when y ′ exceeds 0.25, H _cJ decreases. A more preferable range is 0.05 ≦ y ′ ≦ 0.2.

The sum (y + y ′) of the atomic ratio (y) of Co and the atomic ratio (y ′) of Mg is 0.25 ≦ y + y ′ ≦ 0.37. y + y 'is lowered H _cJ and B _r is less than 0.25, y + y' is not preferable because the H _cJ is reduced when it exceeds 0.37. A more preferable range is 0.27 ≦ y + y ′ ≦ 0.35.

n is a value that reflects the molar ratio of (Ca + R + A) to (Fe + Co + Mg), and is represented by 2n = (Fe + Co + Mg) / (Ca + R + A). n is preferably 4 ≦ n ≦ 6. More than 4 and less than 6 when H _cJ, undesirably B _r and H _k / H _cJ is reduced. A more preferable range is 4.5 ≦ n ≦ 5.6.

  As long as the oxide magnetic material of the present invention is an oxide magnetic material having the above composition, the state, shape, etc. are not limited. For example, the state may be a calcined body or a sintered magnet (sintered body), and the shape is a clinker after calcining, a powder of the calcined body, a molded body of the calcined body, It may be a powder of a sintered body.

  When the oxide magnetic material is a calcined body, the calcined body is composed of a ferrite phase having a hexagonal M-type magnetoplumbite structure having the above composition.

  When the oxide magnetic material is a sintered body, the sintered body is composed of a ferrite phase having a hexagonal M-type magnetoplumbite structure having the above composition, or a hexagonal M-type having substantially the same composition as the above composition. It is composed of a ferrite phase having a magnetoplumbite structure and other compositions. The composition other than that is a composition or grain boundary phase present at the grain boundary of the ferrite phase, or a grain boundary phase present at the triple point portion of the grain boundary.

A sintered magnet (sintered body) is generally added with a sintering aid such as SiO ₂ or CaCO ₃ during firing in order to generate a liquid phase and promote sintering. Most of the added SiO ₂ , CaCO _3, etc. forms a grain boundary phase at the grain boundary of the ferrite phase. The oxide magnetic material of the present invention includes a sintered magnet to which these sintering aids are added, but when a sintering aid such as SiO ₂ or CaCO ₃ is added, the numerical value of x and the numerical value of n in particular. May change greatly and deviate from the composition range. The sintered magnet added with these sintering aids to form a grain boundary phase will be described in detail in “[2] Ferrite sintered magnet” below.

  “Has a hexagonal M-type magnetoplumbite structure” means that the X-ray diffraction pattern of the hexagonal M-type magnetoplumbite structure is measured when the X-ray diffraction of the calcined body is measured under general conditions. Mainly observed. The presence of foreign phases (orthoferrite, spinel phase, etc.), impurity phases, unreacted raw material powders, etc. observed in very small amounts (about 5% by mass or less) by X-ray diffraction or the like is allowed. Quantification of heterogeneous phases from X-ray diffraction can be performed by a technique such as Rietveld analysis.

[2] Ferrite sintered magnet The ferrite sintered magnet of the present invention has a ferrite phase having a hexagonal M-type magnetoplumbite structure, and a grain boundary phase essentially containing Si, and contains at least Ca and a rare earth element. The composition ratio of the R element, which is one kind of essential elements including La, Ba, and / or Sr, the A element, Fe, Co, and Mg metal elements,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio are 0.288 ≦ x ≦ 0.6, 0 ≦ x ′ ≦ 0.2, 0.07 ≦, respectively. y ≦ 0.3,0 <y '≦ 0.2,0.18 ≦ y + y' ≦ 0.37, and is a numerical value satisfying 3.08 ≦ n ≦ 6.) is represented by two in terms of SiO ₂ in the entire ferrite sintered magnet Contains Si by mass or less.

As described above, when a ferrite sintered magnet is generally produced, a sintering aid such as SiO ₂ or CaCO ₃ is added in order to generate a liquid phase at the time of firing to promote sintering. For example, after adding ₂ % by mass of SiO ₂ to the above-mentioned calcined oxide magnetic material and 2% by mass of CaCO ₃ in terms of CaO, pulverizing, molding and firing, the composition of the entire sintered magnet The Ca atomic ratio is relatively increased, and other elements are relatively decreased by the inclusion of Si. Therefore, the lower limit of R element (x) was 0.4 in the calcined body, but it was reduced to 0.288 in the sintered magnet. Similarly, the lower limit of Co (y) was 0.1 to 0.07, and the atomic ratio of Co and Mg The lower limit of the total (y + y ') decreases from 0.25 to 0.18, and the lower limit of n decreases from 4 to 3.08.

  Thus, the composition of the obtained sintered magnet deviates from the composition range of the oxide magnetic material (in this case, the calcined body) depending on the amount of the sintering aid added. The sintered ferrite magnet according to the present invention is also a sintered magnet to which such a sintering aid is added and a grain boundary phase is formed. In the sintered ferrite magnet of the present invention, upper limit and lower limit of Ca (1-x-x ′), R element (x), A element (x ′), Co (y), Mg (y ′) and n The reason is the same as that of the oxide magnetic material described above.

The ferrite sintered magnet of the present invention is obtained by adding SiO ₂ and CaCO ₃ as sintering aids to the above-described oxide magnetic material (calcined body), followed by pulverization, molding and firing. Most of the added sintering aid forms a grain boundary phase at the grain boundary of the ferrite phase. Further, as described above, when the oxide magnetic material is a calcined body, the calcined body is a ferrite having a hexagonal M-type magnetoplumbite structure having the same composition as the composition shown in “[1] Oxide magnetic material”. It is composed of phases. Thus, the sintered ferrite magnet of the present invention has a ferrite phase having a hexagonal M-type magnetoplumbite structure derived from the ferrite phase of the calcined body and a grain boundary phase containing Si. . The grain boundary phase is not observed in the X-ray diffraction pattern but can be confirmed with a transmission electron microscope or the like.

[3] Method for Producing Ferrite Sintered Magnet The method for producing a ferrite sintered magnet according to the present invention includes an element A, which is at least one of Ca, a rare earth element, and contains R as an essential element, Ba and / or Sr. The composition ratio of metallic elements of Fe, Co and Mg is
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio are 0.4 ≦ x ≦ 0.6, 0 ≦ x ′ ≦ 0.2, 0.1 ≦ y ≦ 0.3, 0 <y ′ ≦ 0.25, 0.25 ≦ y + y ′ ≦ 0.37, and 4 ≦ n ≦ 6)), and a ferrite having a hexagonal M-type magnetoplumbite structure Step of preparing a ferrite calcined body containing a phase, to the calcined body, 100% by mass of the calcined body, 2% by mass or less of CaCO _{3 in} terms of CaO and 2% by mass or less of SiO ₂ are added. Crushing the calcined body to which CaCO ₃ and SiO ₂ have been added, obtaining a powder, forming the powder, forming the powder, obtaining the formed body, firing the formed body, It is preferable to include the baking process to obtain.

(a) Preparation process of the calcined ferrite body
The reasons for limiting upper and lower limits of Ca (1-x-x ′), R element (x), A element (x ′), Co (y), Mg (y ′) and n are the same as those of the oxide magnetic material described above. It is the same. An example of a preferable preparation process is given below.

Prepare raw material powders such as CaCO ₃ , La (OH) ₃ , SrCO ₃ , BaCO ₃ , Fe ₂ O ₃ , Co ₃ O ₄ , MgO, etc., and blend them in the preferred ranges based on the aforementioned composition formula .

The raw material powder may be a hydroxide, nitrate, chloride or the like in addition to oxides and carbonates regardless of the valence, or may be in a solution state. Specifically, as the Ca compound, it is preferable to use Ca carbonate, oxide, chloride or the like. As the R element compound, it is preferable to use oxides such as La ₂ O ₃ , hydroxides such as La (OH) ₃ , carbonates such as La ₂ (CO ₃ ) ₃ .8H ₂ O, and the like. As the element A compound, it is preferable to use carbonates, oxides, chlorides and the like of Ba and / or Sr. As the iron compound, it is preferable to use iron oxide, iron hydroxide, iron chloride, mill scale or the like. Examples of the Co compound include oxides such as CoO and Co ₃ O ₄ , hydroxides such as CoOOH, Co (OH) ₂ , and Co ₃ O ₄ · m ₁ H ₂ O (m ₁ is a positive number), CoCO ₃ like carbonates, and _{m 2 CoCO 3 · m 3 Co} (OH) 2 · m 4 H 2 O or the like basic carbonate _{(m 2, m 3, m} 4 are positive numbers) using It is preferable to do this.

Raw material powders such as Ca compound, R element compound, A element compound, Fe compound, Co compound, Mg compound, etc. may be added all at the time of raw material mixing and calcined, or partly added after calcining May be. For example, all of CaCO ₃ , Fe ₂ O ₃ and MgO, a part of La (OH) _{3, and} a part of Co ₃ O ₄ are mixed, mixed and calcined to prepare a calcined body, which will be described later In the process, the remainder of La (OH) _{3 and} the remainder of Co ₃ O ₄ may be added and pulverized, shaped and fired. Regarding MgO, a calcined body excluding only MgO may be prepared, and MgO may be added in the pulverization step. At this time, the calcined body composition may deviate from the calcined body composition in anticipation of adding MgO later.

In the preparatory process of the calcined body, a compound containing B ₂ O ₃ , H ₃ BO ₃ or the like may be added in order to accelerate the reaction during the calcining. The addition of H ₃ BO ₃ is effective in improving the H _cJ and B _r. The amount of H ₃ BO ₃ added is preferably 0.3% by mass or less with respect to 100% by mass of the blended powder or calcined body. The most preferred addition amount is about 0.2% by mass. H ₃ BO amount of ₃ to not obtained the effect of improving the B _r With less than 0.1 wt%, to the B _r many lower than 0.3 wt%. H ₃ BO ₃ has effects such as controlling the size of crystal grains during sintering, so it may be added after calcination (before fine pulverization or before sintering). Both may be added.

  The blending of the raw material powder may be either wet or dry. When the raw material powder is stirred together with a medium such as a steel ball, it can be mixed more uniformly. In the case of a wet type, water is used as a dispersion medium. For the purpose of more stably dispersing the raw material powder, a known dispersant such as ammonium polycarboxylate or calcium gluconate may be used. The mixed raw material slurry is dehydrated to obtain a mixed raw material powder.

  The mixed raw material powder is heated using an electric furnace, a gas furnace or the like, and a hexagonal M-type magnetoplumbite ferrite compound is formed by a solid phase reaction. This process is called “calcination” and the resulting compound is called “calcination”.

  The calcination step is preferably performed in an atmosphere having an oxygen concentration of 5% by volume or more. This is because the solid phase reaction hardly proceeds when the oxygen concentration is less than 5% by volume. A more preferable oxygen concentration is 20% by volume or more.

In the calcination step, a ferrite phase is formed by a solid-phase reaction as the temperature rises and is completed at about 1100 ° C. Below 1100 ° C., unreacted hematite (iron oxide) remains and the magnet properties are lowered. In order to exert the effect of the present invention, it is necessary to set the temperature to 1100 ° C. or higher. On the other hand, if the calcining temperature exceeds 1450 ° C., crystal grains grow too much, and thus a great amount of time is required for pulverization in the pulverization step. Therefore, the calcination temperature is preferably 1100 ° C to 1450 ° C, more preferably 1200 ° C to 1350 ° C. The calcination time is preferably 0.5 to 5 hours. When H ₃ BO ₃ is added before calcination, the reaction is promoted, so that calcination can be performed at 1100 ° C. to 1300 ° C.

(b) Sintering auxiliary agent addition step In the method for producing a sintered ferrite magnet, before the pulverization step, with respect to 100% by mass of the calcined body, 2% by mass or less of CaCO ₃ in terms of CaO, and 2% by mass % Or less of SiO ₂ is added as a sintering aid. With this sintering aid, a liquid phase can be generated during firing to promote sintering, and _HcJ of the ferrite sintered magnet can be improved. CaCO _3, the SiO ₂ both added amount exceeds 2 mass% is not preferable because the B _r and H _k / H _cJ is reduced. The preferable addition amount is 0.7 to 2.0% by mass for CaCO ₃ in terms of CaO, and 0.6 to 1.2% by mass for SiO ₂ .

Although SiO ₂ is most preferably added to the calcined body, a part of the total addition amount can be added before calcining (when the raw material powder is blended). By adding before calcination, the size control of crystal grains during calcination can be performed.

(c) Ferrite calcined body pulverizing step The ferrite calcined body to which the sintering aid is added is pulverized by a vibration mill, a ball mill and / or an attritor to obtain a pulverized powder. The average particle size of the pulverized powder is preferably about 0.4 to 0.8 μm (air permeation method). The pulverization step may be either dry pulverization or wet pulverization, but is preferably performed in combination.

  In the wet pulverization, an aqueous dispersion medium such as water or various non-aqueous dispersion media (for example, organic solvents such as acetone, ethanol, xylene, etc.) can be used. By the wet pulverization, a slurry in which the solvent and the calcined body are mixed is generated. It is preferable to add 0.2 to 2% by mass of known various dispersants and surfactants to the slurry in a solid content ratio. The slurry after wet pulverization is preferably concentrated and kneaded.

In the pulverization step, in addition to the above-described CaCO ₃ and SiO ₂ , additives such as Cr ₂ O ₃ and Al ₂ O ₃ can be added to the calcined body in order to improve magnet characteristics. When these additives are added, Cr ₂ O ₃ is preferably 5% by mass or less, and Al ₂ O ₃ is preferably 5% by mass or less.

(d) Forming step Next, press forming is performed in a magnetic field or in a non-magnetic field while removing the solvent in the slurry. By press molding in a magnetic field, the crystal orientation of the powder particles can be aligned (oriented), and the magnet characteristics can be dramatically improved. Furthermore, in order to improve the orientation, 0.01 to 1% by mass of a dispersant and / or a lubricant may be added. The slurry may be concentrated by centrifugation, filter press or the like before molding.

(e) Firing step The molded body obtained by press molding is subjected to a degreasing step as necessary and then subjected to a firing step. The firing step is performed using an electric furnace, a gas furnace, or the like.

  The firing step is preferably performed in an atmosphere having an oxygen concentration of 10% by volume or more. If the oxygen concentration is less than 10% by volume, abnormal grain growth and heterogeneous phase generation are caused, and the magnet characteristics are deteriorated. The oxygen concentration is more preferably 20% by volume or more, and most preferably the oxygen concentration is 100% by volume.

  The firing temperature is preferably 1150 to 1250 ° C., and the firing time is preferably 0.5 to 2 hours. The average crystal grain size of the sintered magnet obtained by the firing process is about 0.5 to 2 μm.

  After the firing step, a ferrite sintered magnet product is finally completed through known manufacturing processes such as a processing step, a cleaning step, and an inspection step.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
In the composition formula: Ca _0.5 La _0.5 Fe _{10.8-y ′} Co _y Mg _{y ′} , CaCO ₃ powder, La (OH) ₃ so that y and y ′ have the values shown in Table 1-1 and Table 1-2. Powder, Fe ₂ O ₃ powder, Co ₃ O ₄ powder and MgO powder were blended, and 0.1% by mass of H ₃ BO ₃ was added to 100% by mass of the blended powder to obtain a mixed raw material powder. Water is added to this mixed raw material powder, mixed for 4 hours with a wet ball mill, dried and sized, then calcined in the atmosphere at 1300 ° C for 3 hours, and the resulting calcined product is roughly crushed with a hammer mill Thus, coarsely pulverized powder was obtained.

With respect to 100% by mass of the calcined body coarsely pulverized powder, 1.3% by mass of CaCO ₃ powder and 0.6% by mass of SiO ₂ powder are mixed, water is added, and the average particle size by an air permeation method is 0.6 μm with a wet ball mill. A finely pulverized slurry was obtained. The finely pulverized slurry was molded while applying a pressure of about 50 MPa and removing water while applying a magnetic field of about 1 T so that the pressure direction and the magnetic field direction were parallel. The obtained compact was fired in the atmosphere at about 1200 ° C. for 1 hour to obtain a sintered ferrite magnet.

B _r , H _cJ and H _k / H _cJ of the obtained sintered magnet were measured (H _k is the second quadrant of the J (magnetization strength) -H (magnetic field strength) curve). H value when the value is B _r × 0.95). The results are shown in Table 1-1, Table 1-2, and FIGS. 1 to 4 are plots of data of sample Nos. 1 to 6, 7 to 12, 18 to 22, 27 to 30, and 31 to 34. FIG. 1 shows the atomic ratio (y ′) of Mg and B relationship with _r, 2 atomic proportions of Mg (y ') relationship between H _cJ and, Figure 3 is the sum of the atomic ratio of Co and Mg (y + y' relationship between) and B _r, 4 The relationship between the total of the atomic ratios of Co and Mg (y + y ′) and H _cJ is shown.

These results, the sintered ferrite magnet of the present invention, the atomic ratio in the range of 0.25 or less of Mg, although the absolute value of H _cJ will vary depending on the Co atomic ratio (y), H _cJ increases A range exists. This has a high H _cJ are obtained while maintaining high B _r and a high H _k / H _cJ in the range, it can be seen that the particular atomic ratio of Mg has good magnetic properties in a range of 0.05 to 0.2 . Moreover, the range of the total atomic ratio of Co and Mg (y + y ') is from 0.25 to 0.37, although the absolute value of H _cJ will vary depending on the Co atomic ratio (y), a high B _r and a high H _It can be _seen that high H _cJ was obtained while maintaining _{k 2} / H _cJ , and in particular, it has good magnet characteristics in the range of 0.27 to 0.35.

2 and 4 that the absolute value of H _cJ obtained increases as the atomic ratio (y) of Co increases. However, increasing the atomic ratio (y) of Co increases the raw material cost. Reducing raw material cost, and to improve while H _cJ maintaining high B _r and a high H _k / H _cJ, Co atomic ratio (y) is 0.15 ≦ y ≦ 0.24, Mg atomic ratio (y ' ) Satisfies 0 <y ′ ≦ 0.25, and the total atomic ratio of Co and Mg (y + y ′) preferably satisfies 0.25 to 0.37.

Example 2
Composition formula: Ca _1-x La _x Fe _{2n-0.2-y ′} Co _0.2 Mg _{y ′} Example 1 except that the raw material powder was blended so that x, y ′ and n had the values shown in Table 2. A sintered magnet was obtained in the same manner.

B _r , H _cJ and H _k / H _cJ of the obtained sintered magnet were measured in the same manner as in Example 1. The results are shown in Table 2 and FIG. Figure 5 shows the relationship between the La of the atomic ratio (x) and B _r and H _cJ. From these results, the ferrite sintered magnet of the present invention improves H _cJ especially when the atomic ratio of La is in the range of _0.4 to 0.6, particularly in the range of 0.45 to _0.55 , by replacing part of Fe with Mg. It can be seen that high H _cJ is obtained and that the magnetic properties are good.

Example 3
Composition formula: Ca _0.5 La _0.5 Fe _{2n-0.2-y ′} Co _0.2 Mg _{y ′} was calcined in the same manner as in Example 1 except that the raw material powder was blended so that y ′ and n had the values shown in Table 3. A magnet was obtained.

B _r , H _cJ and H _k / H _cJ of the obtained sintered magnet were measured in the same manner as in Example 1. The results are shown in Table 3 and FIG. Figure 6 shows the relationship between the molar ratio n and B _r and H _cJ. From these results, in the sintered ferrite magnet of the present invention, by replacing a part of Fe with Mg, n _c is improved in the range of 4 to 6, especially high H _{cJ in} the range of _4.5 to _5.6. It can be seen that it has good magnet properties.

Example 4
Composition formula: Ca _{0.5-x ′} La _0.5 A _{x ′} Fe _10.5 Co _0.2 Mg _{0.1 In} Example 1 except that the raw material powder was blended so that the A element and x ′ had the elements and atomic ratios shown in Table 4. A sintered magnet was obtained in the same manner.

B _r , H _cJ and H _k / H _cJ of the obtained sintered magnet were measured in the same manner as in Example 1. The results are shown in Table 4 and FIG. Figure 7 shows the relationship between B _r and H _cJ and the atomic ratio (x ') of the element A. From these results, the ferrite sintered magnet of the present invention improves H _cJ when the atomic ratio of the A element is in the range of ₀ to 0.2, and higher H _cJ is obtained in the range of 0 to _0.15 , particularly 0.03 to 0.1. It can be _seen that even higher H _cJ is obtained in this range, and it has good magnetic properties, and when Ba is used as the A element, it has good magnetic properties like Sr.

Example 5
A calcined body coarsely pulverized powder was prepared in the same manner as in Example 1 except that the raw material powder was blended so that the composition formula was Ca _0.5 La _0.5 Fe _10.5 Co _0.2 Mg _0.1 . The same procedure as in Example 1 was conducted except that 100% by mass of the coarsely pulverized calcined powder was mixed with CaCO ₃ powder (shown in terms of CaO in the table) and SiO ₂ powder shown in Table 5. Thus, a sintered magnet was obtained.

B _r , H _cJ and H _k / H _cJ of the obtained sintered magnet were measured in the same manner as in Example 1. The results are shown in Table 5. From these results, it can be seen that good magnetic properties can be obtained when CaCO ₃ is in the range of 0.7 to 2.0 mass% in terms of CaO and SiO ₂ is in the range of 0.6 to 1.2 mass%.

Example 6
Composition formula: Ca _0.5 La _0.5 Fe _10.5 Co _0.2 Mg _0.1 (Sample No. 20), Ca _0.5 La _0.5 Fe _9.4 Co _0.2 (Sample No. 49) and Ca _0.5 La _0.5 Fe _10.1 Co _0.3 (Sample No. 87) A calcined body coarsely pulverized powder and sintered magnet were obtained in the same manner as in Example 1 except that the raw material powder was blended.

  The obtained calcined body and sintered metal elements were analyzed by inductively coupled plasma (ICP) emission analysis. The quantification results of the metal elements are shown in Table 6 and Table 7, respectively, and the atomic ratio and molar ratio calculated from these analysis results are shown in Table 8 and Table 9, respectively. From Table 6 to Table 9, the calcined bodies and sintered magnets of the examples of the present invention (sample No. 20) have the La and Co contents greatly reduced by replacing part of Fe with Mg. I understand that.

Example 7
Composition formula: Ca _{1-x-x '} La _x Sr _x' Fe _{2n-0.2-y '} Co _0.2 Mg _{y' so} that x, x ', y' and n have the atomic ratio and molar ratio shown in Table 10 A sintered magnet was obtained in the same manner as in Example 1 except that the raw material powder was blended.

B _r , H _cJ and H _k / H _cJ of the obtained sintered magnet were measured in the same manner as in Example 1. The results are shown in Table 10 and FIG. These samples are all comparative examples, sample Nos. 88 to 91 are known SrLaCo ferrites disclosed in Patent Documents 1 and 2, etc., and sample Nos. 92 to 95 are sample Nos. 18 to 18 of Example 1. This is SrLaCo ferrite in which all of Ca in 21 CaLaCo ferrite is replaced with Sr. These sintered magnets do not contain Ca in addition to the sintering aid. Figure 8 shows the relationship between B _r and H _cJ and the atomic ratio of Mg (y '). From these results, it can be seen that SrLaCo ferrite does not have the effect of improving the magnet properties due to Mg substitution like CaLaCo ferrite.

Claims (9)

The composition ratio of Ca, R element which is at least one of rare earth elements and essentially contains La, Ba element and / or Sr element A, Fe, Co and Mg metal elements,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y and y ′ representing the atomic ratio of R element, A element, Co and Mg, respectively, and n representing the molar ratio,
0.4 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.15 ≦ y ≦ 0.24 ,
0.05 ≦ y '≦ 0.2 ,
0.25 ≦ y + y ′ ≦ 0.37, and
4 ≦ n ≦ 6
It is a numerical value that satisfies An oxide magnetic material characterized by the following:   2. The oxide magnetic material according to claim 1, wherein x is a numerical value satisfying 0.45 ≦ x ≦ 0.55.   3. The oxide magnetic material according to claim 1, wherein x ′ is a numerical value satisfying 0 <x ′ ≦ 0.15.   4. The oxide magnetic material according to claim 3, wherein x ′ is a numerical value satisfying 0.03 ≦ x ′ ≦ 0.1. 5. The oxide magnetic material according to claim 1 , wherein the y + y ′ is a numerical value satisfying 0.27 ≦ y + y ′ ≦ 0.35. 6. The oxide magnetic material according to claim 1 , wherein n is a numerical value satisfying 4.5 ≦ n ≦ 5.6. A ferrite phase having a hexagonal M-type magnetoplumbite structure;
A ferrite sintered magnet having a grain boundary phase essentially containing Si,
The composition ratio of Ca, R element which is at least one of rare earth elements and essentially contains La, Ba element and / or Sr element A, Fe, Co and Mg metal elements,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio,
0.288 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.15 ≦ y ≦ 0.24 ,
0.05 ≤ y '≤ 0.2,
0.18 ≦ y + y ′ ≦ 0.37, and
3.08 ≦ n ≦ 6
It is a numerical value that satisfies The sintered ferrite magnet is characterized in that it contains 2% by mass or less of Si in terms of SiO _{2 in the} entire sintered ferrite magnet. The composition ratio of Ca, R element which is at least one of rare earth elements and essentially contains La, Ba element and / or Sr element A, Fe, Co and Mg metal elements,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio,
0.4 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.15 ≦ y ≦ 0.24 ,
0.05 ≦ y '≦ 0.2 ,
0.25 ≦ y + y ′ ≦ 0.37, and
4 ≦ n ≦ 6
It is a numerical value that satisfies )
Preparing a calcined ferrite body containing a ferrite phase having a hexagonal M-type magnetoplumbite structure;
The step of adding to the calcined body 100% by mass of the calcined body, 2% by mass or less of CaCO ₃ and 2% by mass or less of SiO ₂ in terms of CaO,
Crushing the calcined body to which CaCO ₃ and SiO ₂ have been added to obtain a powder;
The manufacturing method of the ferrite sintered magnet characterized by including the shaping | molding process which shape | molds the said powder and obtains a molded object, and the baking process which bakes the said molded object and obtains a sintered compact. A ferrite phase having a hexagonal M-type magnetoplumbite structure;
Having a grain boundary phase essentially containing Si,
The composition ratio of Ca, R element which is at least one of rare earth elements and essentially contains La, Ba element and / or Sr element A, Fe, Co and Mg metal elements,
General formula Ca _{1-x-x '} R _x A _x' Fe _{2n-y-y '} Co _y Mg _y'
(However, x, x ′, y, y ′ representing the atomic ratio of R element, A element, Co and Mg, and n representing the molar ratio,
0.288 ≦ x ≦ 0.6,
0 ≦ x ′ ≦ 0.2,
0.15 ≦ y ≦ 0.24 ,
0.05 ≤ y '≤ 0.2,
0.18 ≦ y + y ′ ≦ 0.37, and
3.08 ≦ n ≦ 6
It is a numerical value that satisfies ) And is a method for producing a ferrite sintered magnet containing 2 mass% or less of Si in terms of SiO ₂ out of the entire ferrite sintered magnet,
Preparing a ferrite calcined body,
The step of adding to the calcined body 100% by mass of the calcined body, 2% by mass or less of CaCO ₃ and 2% by mass or less of SiO ₂ in terms of CaO,
Crushing the calcined body to which CaCO ₃ and SiO ₂ have been added to obtain a powder;
The manufacturing method of the ferrite sintered magnet characterized by including the shaping | molding process which shape | molds the said powder and obtains a molded object, and the baking process which bakes the said molded object and obtains a sintered compact.

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