JPH0319202A - Strontium-ferrite magnet in excellent magnetic properties - Google Patents

Abstract

PURPOSE:To augment the residual flux density and the coercive force by a method wherein the title strontium.ferrite is composed of a sintered body containing CuO, SiO2, Sb2O3 in respectively specified contents as well as the remaining content of SrO.nFe2O3 where n represents 5.8-6.0. CONSTITUTION:The title strontium.ferrite magnet can be manufactured by sintering it so that it may be composed of 0.3-0.6wt.% of CaO, SiO2 and 0.05-0.15wt.% of Sb2O3 as well as the remaining substantial wt.% of SrO.nFe2O3 where n represents 5.8-6.0. Through these procedures, the strontium.ferrite magnet especially for electronic range in combination of high Bv with high Hc can be manufactured.

Description

[Detailed description of the invention] Industrial field in Icheon> The present invention relates to ferrite magnets, and particularly relates to residual magnetic flux density (
B') and coercive force (irlc) are both high. <Prior art> In order to improve the performance of sintered strontium ferrite magnets, it is necessary to (1) increase the density of the sintered body, (2)
) grain size in political world I1! (3) increase the degree of crystal orientation. As a method of satisfying conditions (1) and (2) of these, it is known that it is effective to add a small amount of elements other than the strontium ferrite component. For example, JP-A-55-
141711 discloses that the addition of CaO and S10 is extremely effective in improving the characteristics of sintered magnets. Conventionally, the magnetic properties required for a high-performance magnet for microwave ovens are Br≧43000, illc≧29000e.
However, the characteristics of the two tend to contradict each other, and when sintered under conditions that increase the residual magnetic flux density (Ilr), the coercive force (lllc) decreases. In order to improve the residual magnetic flux density, it is advantageous to strengthen the degree of crystal orientation and increase the sintering density. Therefore, it is preferable to increase the firing temperature and make the crystal structure relatively large. On the other hand, the coercive force (llc) requires that the size of the crystal after sintering be suppressed to a certain level in order to obtain single domain grains (0.94 m for strontium ferrite). Therefore, “Powders and Powder Metallurgy” Volume 3
4 @ No. 4 June 1987 No. 30-32 True,
In order to control the particle size, various amounts and ratios of Cab and Slow are being investigated. CaO and Sin. The sintering mechanism of strontium ferrite added with CaO-S10. -Sr0 ・6
Fears' ternary solid solution grows locally, and as the sintering temperature rises, a grain boundary liquid phase with good wettability is formed between the strontium and ferrite crystal grains, suppressing crystal length and suppressing crystal growth. It is liquid phase sintering that works on densification, and Cab,
Addition amount of Sing and their addition ratio (CaO/Sin
g) has a subtle effect on particle size control. For example, when the amount of CaO added increases (Cab/SiOi ratio increases), grain growth is promoted, and the amount of Sing increases (Cab/SiOi ratio increases).
When the O2 ratio is small), grain growth is suppressed. Furthermore, it has already been disclosed in JP-A-55-138204 that a small amount of N10 is added to Cab, SiOgj at the same time to suppress grain growth and improve coercive force (ILLC). However, CaO and StO. , or the simultaneous addition of Cab, Sing, and /V t O z may cause locally abnormal growth of crystal grains when the sintering temperature is high, resulting in a significant decrease in i11c.
As mentioned above, high-performance magnets for microwave ovens must have high Br and high illc at the same time.
For combined addition of O+ Sing and 8 lx's, the optimum conditions such as their addition amount and CaO/SiOz ratio are +1! !
It was difficult to grasp. Problems to be Solved by the Invention> In view of the above-mentioned current state of strontium ferrite, the present invention has been developed to obtain excellent magnetic properties in B' and illc without producing abnormal crystal structures even at high sintering temperatures, and in particular High performance IF stone characteristics for microwave oven (Br>4300G
, illc≧29000o). <Means for solving the problem> That is, the present invention solves the problem by using strontium ferrite SrO.nF.
axos (n − 5.8 to 0.0) with calcium oxide (Cab) as a subcomponent of 0.3 to 0.6
wt%, silicon dioxide (Sins) from 0.3 to 0.6
wt% and antimony oxide (Sb*03) 0.05
~0. By adding 15 wt% every time, abnormal growth of crystal grains during sintering is suppressed, and evenness is achieved. A fine crystal structure was obtained. As a result, a strontium ferrite magnet with excellent magnetic properties in B' and illc was obtained. Effect> Traditionally, the addition effect of Sing has been to increase the concentration of crystal grains.
It is known that magnets with high coercive force can be obtained by suppressing magnetization. Eight Itch also Sin. The same effects as those of Sing have been recognized, but the effect of coarsening the crystal grains is smaller than that of Sing. On the other hand, CaO, unlike SiO 8 It's, promotes the ferritization reaction and causes coarsening of crystal grains. It is known to have the effect of increasing density. However, the effect of adding SiO₂CaO and SbzOs at the same time has not been investigated. The present inventors recognized the above problems and conducted various studies, and as a result, CaO
+ We discovered that high-performance magnets can be obtained by simultaneously adding SIOt and SbzOs. Next, in the present invention, Ca
b, Sing and Sb! The reason for limiting the amount of 03 added is explained below. Sing: If it is less than 0.3 wt%, the coercive force will be low, and if it exceeds 0.6 wt%, the coercive force will be high, but the residual magnetic flux density will be low, which is not desirable in practical terms. CaO: If it is less than 0.3 wt%, the coercive force will be high but the residual magnetic flux density will be low. On the other hand, if it exceeds 0.6 wL%, the thermal viscosity will be accelerated, crystal grains will become coarser, and the coercive force will drop significantly, which is not preferable.

SbzOs: In the above limited range of CaO and Sing amounts, if SbmOt is less than 0.05 wL%, the coercive force will be low, and if it exceeds 0.15 wt%, the magnetic east density will drop significantly, which is not preferable. Therefore, the content of additives is CaO: 0.30-0.60wt%, Si(h:
0.30-0.60wt%, SbzOs: 0.
05 to 0.15 wt%. If n4i (molar ratio of FetOi/SrO): n{a of strondium ferrite is less than 5.8, the residual magnetic flux density will be high but the coercive force will be low, which is not desirable in practical terms. On the other hand n{! ! If it exceeds 6, hematite becomes excessive and the magnetic properties deteriorate, which is undesirable. Therefore, the n value was set to 5.8≦n≦6.0. Examples are shown below to clarify the effects of this invention. Examples Example 1 A basic composition of raw materials consisting of strontium ferrite with a molar ratio of Fi3tOz/SrO = 6 was mixed in a Henschel mixer, then pelletized and calcined at 1260°C. This calcined left was coarsely ground using an atomizer. Next, the additives shown in Table 1 were added using an attritor, mixed in the form of a 40w1% slurry, and pulverized.
After finely pulverizing the average particle size (a) to 0.8μ, the slurry was centrifuged in a ram (40→60% slurry) 7
It was molded under a pressure of It/C- in a magnetic field of 000 ersted. After thoroughly drying the compact, it was baked at 1250°C for 3 hours. The magnetic properties of the obtained sintered body are shown in Table 1. As is clear from Table 1, in addition to CaO and SiO2,
Further, by adding 0.05 to 0.15% of SbgOs in a composite manner, a material in which both B' and illc sufficiently satisfy the characteristics of a high-performance magnet for microwave ovens is obtained, and the effect of adding antimony is clear. However, as in samples Nn26 to 30, Sbg03 was added to 0.
When 20 wt% is added, illc improves, but Br decreases, making the properties unfavorable. Also, like wipe ill~5, tab, 510. As for additives, as the amount of Cano increases, Br tends to increase, but 111c decreases on the contrary. On the other hand, samples like Samples 6 to 10 in which MtOs was added in addition to Cab, SiO richness decreased Dr but l
llc will be improved. However, due to its low Br, it does not fully satisfy the characteristics as a high-performance magnet for microwave ovens. From the above results, appropriate amounts of Can, SiO* and Sbt
It can be seen that the combined addition of Os modifies both Br and lflc. Figure 1 shows the results of microstructural observation using an optical a-microscope after mirror polishing and etching treatment for Wiryokakure 3 and N[Ll3. FIG. 1(a) (Sample Shame 13) according to the present invention
) has a relatively uniform and fine grain size, and the IJI microstructure shows that it has excellent magnetic properties. On the other hand, in the case of the conventional method as shown in Fig. 1 (c) Wipe cutter 3, the crystal structure is non-uniform and coarse grains can be seen locally.
This is thought to be causing a decline in ? As a result of qualitative analysis of additives using IMMA, C
It was found that ab, SlO■ is concentrated at the grain boundaries, but sb is evenly distributed within the grains (solid solution within the grains). Although it is not clear, some kind of suppressive effect is working! II
It is measured. Example 2 Strondium with molar ratio Fe,0,/SrO = 6
The raw materials for the basic composition consisting of ferrite were mixed and calcined in the same manner as in Example 1. After pulverization, the additives shown in Table 2 were added using an attritor, and samples were prepared in the same manner as in Example 1 to obtain the magnetic properties shown in Table 2. As is clear from Table 2, CaO: 0.3 to 0.6
wt%. Sins: 0.3 to 0.6 wt%, SbtOs: 0.05 to 0. By simultaneously adding 15%, magnetic properties suitable for a high-performance microwave oven magnet can be obtained. Example 3 Molar ratio of PezO,/SrO (n value) -5.6,
5.7. 5.8.5.9. The basic & IIFfA raw materials consisting of 6.0 strontium ferrite were mixed, calcined, and pulverized in the same manner as in Example 1, and then the additives shown in Table 3 were added in an attritor, and then the Prepare a sample using the same method as in 1.3.j! The magnetic properties shown are obtained. As is clear from Table 3, magnetic properties suitable for a high-performance microwave oven magnet were obtained in the range of 5.8≦n≦6.0. <Effects of the Invention> The present invention provides high Br and high 11L that surpass the conventional ones.
A strontium ferrite magnet is obtained that is particularly suitable as a high-performance magnet for microwave ovens, and is highly effective in terms of energy saving.

[Brief explanation of drawings]

Claims (1)

[Claims] CaO: 0.3 to 0.6 wt%, SiO_2: 0.3
~0.6wt%, Sb_2O_3:0.05-0.15
wt%, and the remainder is substantially SrO・nFe_2O_3
A strontium ferrite magnet with excellent magnetic properties, characterized by being a sintered body having a composition ratio of n=5.8 to 6.0.