JPS6287459A - High density ferrite and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a high-174 ferrite and a method for producing the same. , : VTR, h' DD, RD r), etc. 4m, I'; Recording/re-recording on high-coercivity magnetic recording media such as Kelmetal tape, vapor-deposited tape, etc.
'iI! Mn with high magnetic flux density used in I
This article relates to Zn-based ferrite and its packaging method.

(Prior art and its problems) Conventionally, 44 for magnetic recording and reproduction of VTR etc.
As a material, a ferrite abrasive material represented by Mn-Zn ferrite is used.
After calcining the ferrite raw paddy unmixed mixture containing ~54% to give a ferrite conversion rate of about 80% or 1 degree, the calcined product is pulverized and molded into a predetermined shape. The molded product obtained by
After firing at a temperature below 200°C, approximately equilibrium oxygen partial pressure (
(0.1-100% as oxygen depth 7), below 1250
It is sintered at a temperature of 71°C and then fried (by the so-called vacuum firing method, which controls the particle size and magnetic properties. After 411.9001' uI, the ferrite conversion rate of the molded body reaches approximately 100%. It is made to be.

However, the ferrite having the iron oxide N, 11 composition as shown in 1-1 has a saturation magnetic flux density (n, o) of 560
Since it is less than 0G (Gauss), it could not be used as a ferrite for recording and reproducing high coercivity magnetic recording media such as metal tapes.

In addition, as one of the methods for increasing the density of ferrite,
A method of firing the above-mentioned molded body under pressure using a hot isostatic pressing (IIIP) method or a hot pressing (IP) method is also being considered.
It is recognized that a sintered ferrite body with a porosity of 1% or less can be obtained, but in the case of a high-density ferrite body with a reduced porosity, it is reheated to a temperature of 1000°C or higher. As a result, the pores in the ferrite body are revived and the ferrite body becomes a high-porosity ferrite body again.Therefore, such a tc ferrite body is made into a single crystal by a small crystallization method using a solid phase reaction. It was a problem to become

On the other hand, in Japanese Patent Application Laid-open No. 59-64599, mol 11-
So, 61.5-65% of ferric oxide and 10-65% of zinc oxide
20% manganese oxide and 28.5 to 15% manganese oxide. L7 is produced by the so-called Bridgeman manufacturing method, which is grown from a melt (liquid phase). With this ferrite composition, the saturation magnetic flux density is (R,.) is 5500
It has been revealed that it is possible to obtain ferrite that is GJ sotho.

However, in order to obtain a ferrite body with a ferric oxide content exceeding 60 mol%, when a ferrite raw powder mixture containing a high proportion of ferric oxide and iron is calcined in air, the ferrite is conversion rate is 40-6
When the calcined product with such a ferrite conversion rate is pulverized and further formed into a predetermined shape, the resulting molded product is fired using the above-mentioned vacuum firing method.
The ferrite conversion rate is approximately 1 at the temperature after 101) O''C91i.
00%, that is, the hematite in the sintered body completely disappears, and therefore, even after the subsequent sintering operation at a temperature of 1250°C or higher, it is not sufficiently densified, and the porosity of the sintered body obtained is ( It was extremely difficult for Kawahara to make it 1.01% or more.
1 bow:,: ,r,<Because there are many pores, it is tF-crystallized by solid-state reaction. Todoroki 6. Two “
In addition to making it difficult to control small crystallization, there are inherent problems such as the formation of crystal grains, or the occurrence of gastric crystals. There is a problem 4) that pores remain.

(Solution Means) Here, the present invention was made against the background of the above-mentioned circumstances. -There was a te,
Another object of the present invention is to provide a high-density film that can be advantageously used in heads for high-coercivity magnetic recording media. The purpose is to provide a high-density ferrite that does not have a t-membered ferrite with the sliding properties of the henode.Another purpose is to achieve a low single crystallization temperature in a single crystallization method using an in-phase reaction, and to reduce the generation of heterogeneous species. 11: We provide a high-density f-light that eliminates the problem of resuscitation of pores due to heating.

In order to achieve this object, the present invention is characterized by firing a ferrite material containing 60 to 68 mol% of ferric oxide and having a matite phase together with a ferrite phase. A method for producing high-density ferrite, comprising: (a) the ferrite material having a density of 0.01 to
In an atmosphere with an oxygen concentration of 50%, the hemakite phase gradually decreases.I! Bake while shrinking, and 1100~1
The first fired culm that eliminates the hematite phase at a temperature of 6N at 250°C, and (l) the ferrite material in which the hematite phase is extinguished are heated to a temperature of 0.1 to 100%.
% of oxygen concentration at a temperature higher than 1250°C to densify the first firing.
``It consists in including mode.

In addition, malting obtained according to such a high-density ferrite manufacturing method contains 60 to 68% ferrous oxide and 1
High-density ferrite having a composition consisting of 0 to 20% zinc oxide and 30 to 12% manganese oxide has a saturation magnetic flux density (B+o) of 5800 G (Gauss) or more14 and a porosity of 0.01% or less. Yes, month 11 (10℃1λ
It has the characteristic that the porosity does not substantially increase during heat treatment at a temperature of about 100 yen. It can be suitably used as a head for high coercivity magnetic recording media, and can also be used for magnetic and gutter sliding. 11 dynamic characteristics! It can be suitably used as a rope material.

Here, the porosity increases substantially1. This means that the porosity before and after heating is within the measurement error range.
This does not mean that almost nothing changes. stop"(
In this case, within the measurement error range can be considered to be a change within a range of approximately ±50% of the measured value, based on the accuracy of porosity measurement.

The first firing step in the high-density ferrite manufacturing method according to the present invention described above generally includes a plurality of stages of temperature raising steps, and the final temperature raising step increases the ferrite material strength to 100 to 1250. The material is heated to a temperature IW of .degree. C., so that the hemacite phase in the ferrite material can be substantially eliminated. Further, in the first firing step, the ferrite material is heated to a temperature of at least 800° C. to reduce the hemacite phase in the ferrite material.

Further, according to a preferred embodiment of the present invention, the ferrite material has a molar ratio of ferric oxide of 63 to 65% and 10 to 10% of ferric oxide.
It has a composition consisting of 15% zinc oxide and 27 to 20% manganese oxide, and the oxygen concentration in the firing atmosphere in the first firing step is 0.1 to 10%, and The oxygen concentration in the firing atmosphere in the second firing step will be 1 to 20%.

(Long-term explanation and effects of the structure) By the way, the ferrite material number used in the present invention is [, ferric oxide (Fez O!) is 60 to 6]
having a composition containing 8 mol%,
A raw material powder mixture of Mn-Zn-based Ft--I which gives such a composition is calcined in accordance with a conventional method, and then pulverized, and a molded body is formed into an appropriate shape such as a block. is θ) which is suitable for use as the ferrite material. In addition, such a molded body is -・
Finally, about 40 to 60% by weight is composed of a ferrite phase, and the remaining 60 to 40% by weight is composed of an unreacted phase mainly composed of a hematite phase.

Also, the composition number of the L-light material, r, as it is,
The composition of the high-density ferrite obtained by firing it is 7. The high-density ferrite with a high saturation magnetic flux density (n, .) obtained according to the present invention has a molar ratio of 60
~68% ferrous oxide (FO203), 10-20%
Ferra (1) having a composition consisting of In oxide of
・Obtained using materials, especially ferric oxide 63~
A ferrite compound having a composition of 65:el%, zinc oxide 0~15 mol%, and manganese oxide 27~20 mol% is preferably used, thereby achieving a saturation magnetic flux density of 5800 G1.
11, preferably 600 (1 G) or more, a high density ferrite t can be advantageously obtained.

Then, a ferrite material (calcined compact) having such a ferrite phase and a hematite phase is first prepared using (1, (11 to 50% oxygen? m1iF, He,
The hematite phase in the ferrite material is gradually reduced by firing in an atmosphere of Ar, N2, etc., and the hematite phase is substantially eliminated in a temperature range of 1100 to 1250°C. (
(first firing step). In other words, in this first firing step, the temperature and oxygen partial pressure (concentration ) will be adjusted.

Note that the oxygen concentration in this firing atmosphere is 1% to 0.0%.
．． (When it comes to ferrite material) The progress of lrite is rapid, and in the low crystallinity region, the matite phase virtually disappears and turns, so the porosity of the ferrite material is reduced to 1.
- Minutes - (! 1 ~ There is an unforeseen problem, and when the oxygen concentration exceeds 50%, the progress of ferrite formation is slow, and the disappearance of the hematite phase is delayed into the second firing process, so the sintering There is a problem that the old 1411 large pores remain in the body.

Furthermore, if the hematite phase substantially disappears at a temperature below 1+00°C and reaches L7, the ferrite material cannot be sufficiently densified in the second firing process, and the porosity of the final fired body cannot be sufficiently increased. It becomes difficult to reduce the Furthermore, if the hematite phase disappears at a temperature of 41 degrees above 1250 degrees Celsius, there is a problem in that large pores are generated in the second firing step.

Furthermore, the firing temperature of the ferrite material in this first firing step is generally 800° C. or higher. However, if the temperature is lower than 800° C., the progress of ferrite formation is slow and an effective reduction reaction of the hematite phase cannot be induced. In the first firing step, a method is adopted in which the fillerite material is fired using a temperature raising operation that raises the temperature in stages or continuously. ,
According to the multiple stages of JF7 m T culm, the firing temperature is increased step by step, and by the final stage of about 4T, the ferrite crystal is heated to a temperature of 1100 to 1250 °C,
The hematite phase in the ferrite material is made to disappear.

More specifically, a preferred stepwise temperature raising operation in the first firing step of the present invention is a first temperature raising step in which the temperature is gradually raised from about 800°C to reach a temperature lower than 1200°C; Subsequently, a first holding step consisting of holding at the reached temperature for a predetermined time, and subsequent 1100 ~] 250
The process includes a second W temperature step in which the temperature is raised to a predetermined temperature in the range 'c', and a second holding step in which the temperature is held at that temperature for a predetermined time to substantially eliminate the hematite phase. The heating speed at that time is usually 800
℃ up to 150~b. Also, in the second and second YIA process, both are 30~b. Next, the ferrite material whose hematite phase has been eliminated in the first firing process is further heated in the second firing process. In the process, it is fired and further densified. In this first firing process &I a) Firing! As the surrounding atmosphere, an atmosphere is used that allows 0.1% to 100% oxygen to be diverted, and this oxygen concentration of 1% ultimately reduces the porosity to 0.1%. O decreases to less than 1%.
This is necessary to control the grain size, ferrite crystal grain size, and atmospheric characteristics f'l. Note that the components other than oxygen in this firing atmosphere are inert gas components such as He, Ar, N2, and the like. In addition, the firing temperature is 12
It is necessary to use temperatures above 50°C, which
This makes it possible to proceed with effective sintering, thereby obtaining a dense ferrite sintered body in which the pores are effectively reduced.

The ferrite sintered body subjected to the first firing process and the second firing process according to the present invention is a high-density ferrite with a porosity of 0.01% or less, and is recorded in Record 1.
It has excellent workability as T11 density ferrite for lr4, and also prevents head chipping and ift when sliding with magnetic tape. + Eye R to the powder pores:! 7E ”1
It has the feature that it does not cause problems such as the generation of noise.

In addition, since it is a pressureless sintering method, the cost I/Hl 1
) is cheaper than the press method and press method, and requires large equipment 4! In addition, it has the characteristic of being a simple process, and it has been reported that pore resuscitation can be effectively suppressed even by heat treatment at temperatures above 1000°C. - Even if ferrite (polycrystalline ferrite) is made into a single crystal, the porosity does not increase, and the porosity of the resulting single crystal can be reduced to 0.01% or less.

Furthermore, the composition of the high-density ferrite obtained according to the present invention is changed to Mn, which has a composition consisting of 60 to 69 mol% ferric oxide, 10 to 20 mol% zinc oxide, and 30 to 12 mol% manganese oxide. - By using Zn-based ferrite, it is possible to obtain a high-density ferrite with a saturation magnetic flux density (Rho) of 5 gaaa or more, preferably 60 (JOG or more -1-), which is a magnetic recording medium with high coercive force. It is advantageously used as a recording/reproducing head material for metal tapes, vapor-deposited tapes, etc.

Note that the present invention has 1. The porosity is the area occupied by pores in any cross section of the sample expressed as a percentage, a;: j/, and is specifically determined by U7 as follows. That is, an arbitrary cut surface of a predetermined sample is polished, and the polished surface is inspected at a magnification of 1000 times using a metallurgical microscope to determine the diameter of pores in the field of view: d and the number of pores: Measure n, measure the porosity from the pore area relative to the total field area, and calculate the porosity: P according to the formula below.
This is to find the percentage.

l (where d: pore diameter (longer diameter); n: pore diameter d; number of pores; and in the present invention), the ferrite conversion rate indicates the weight %f% of the ferrite phase; The weight of the hematite phase at the time of Ix1 and the weight of the hematite phase after calcination were measured, and the calculation was made assuming that all the disappeared hematite had become the ferrite phase.

Furthermore, the saturation magnetic flux density B1° indicates the saturation magnetic flux density in a magnetic field of 100e.

(Examples) In order to clarify the present invention more specifically, some examples of the present invention will be shown below, but the present invention shall not be construed to be limited by the description of such examples. It goes without saying that it is nothing.

It should be noted that the present invention can be implemented in various embodiments in addition to the detailed description of the present invention and the following examples, and as long as it does not depart from the spirit of the present invention, it is within the knowledge of those skilled in the art. It should be understood that all of the various embodiments that can be implemented based on the present invention fall within the scope of the present invention.

Example 1 A ferrite raw material having a composition consisting of ferrite oxide obtained by roasting hydrothermally synthesized magnetite, iron: 6+, o%, manganese carbonate: 27.0%, and zinc oxide: 12.0% in molar ratio. The powder mixture was calcined in air at a temperature of about 1000° C. for 2 hours, then pulverized and molded into a predetermined shape.

Then, the obtained molded body as a ferrite material was fired as follows. That is, first, from room temperature to 800℃
up to 150 °C/hr heating rate, and up to 800 °C/hr
The stomach was heated at a heating rate of 40°C/hr from 1000°C to 1000°C, and then held at 1000°C for 4 hours. During this firing, the firing atmosphere had an oxygen concentration of 0. .1% nitrogen atmosphere.Next, the first firing operation was continued by heating at a rate of 17?n of 40°C/hr and holding at 1200°C for 2 hours to remove the .・The four phases were extinguished.In addition, the fired body immediately after the Vl crystallization at 1100°C and the fired body after being held at 1200°C for 2 hours were taken out midway, and the cut surface inside the fired body was subjected to X-ray diffraction.
When we investigated the phase difference, we found that in the former case, the hematite phase remained, while in the latter case, it was 100% solid phase, and it was confirmed that the hematite phase had disappeared during this period. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%.

Furthermore, after that, the temperature was heated at a Chinot temperature rate of 150°C/hr for 13 minutes.
A second firing operation was carried out by raising the temperature to 'On' and holding it at that temperature for 8 hours. Also, during this firing, the firing temperature was set to a nitrogen atmosphere with an oxygen concentration of 5%. .

After the firing, a cooling step of 1100°C or lower is performed in a nitrogen atmosphere to obtain the desired ferrite fired body (
A polycrystalline substance) was obtained. The obtained polycrystalline material had an average grain size of 9.8 μm, a porosity of 0.01%, and a discontinuous grain growth temperature of 1340°C.

In addition, the obtained polycrystalline body was divided into 511 × 5 dragon ×
It was cut into pieces with a size of 10 fins, heat treated as follows, and the change in porosity after the heat treatment was examined.

First, the kidney temperature was heated from room temperature to 1100°C at a rate of 300°C/hr, and the atmosphere during this period was nitrogen. After that, further
Raise the temperature to 1300°C at 300°C/hr, and
Holds time. The atmosphere during this time was a nitrogen atmosphere with an oxygen concentration of 1 fl-5%. Then, the temperature was lowered at a rate of 300°C/hr,
Then, it was cooled from 1100° C. in a nitrogen atmosphere to obtain a heat-treated ferrite fired body.

Example 2 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite was 762.5%, manganese carbonate: 26.5%, and zinc oxide: 11. (A ferrite raw material powder mixture of #:Il composition consisting of 1% was heated at a temperature of about 1000°C in air for 2
After being calcined for a period of time, it was crushed and molded into a predetermined shape.

The obtained molded body was then fired as follows.

That is, from room temperature to 800°C, the heating rate is 150°C/hr, and from 800°C to 1000°C, it is 40°C.
The temperature was increased to W at a heating rate of /hr, and the temperature was further maintained at 1000°C for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 0.5%. Then, the temperature was increased at a rate of 40°C/11r, and further to 1220°C.
The molded body was held at a temperature of 2 hours to eliminate the hematite l-phase in the molded body. In addition, when we took out the fired body immediately after raising the temperature to 1100° (:) and the fired body after holding it at 1220°C for 2 hours, and examined the cut surface inside the fired body using an X-ray diffraction method, it was found that the former had hematite. It was confirmed that the latter phase remained 100% ferrite phase, and that the hematite phase had disappeared during this period.During this period, the atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%.

Next, the final firing operation was carried out by raising the temperature to 1300° C. at a heating rate of 150° C./hr and maintaining that temperature for 8 hours. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 3%. and,
After firing, a cooling step of 1100° C. or lower was performed in a nitrogen atmosphere to obtain the desired elite fired body (polycrystalline body).

The obtained polycrystalline body had an average grain size of 8.9 μm, a porosity of 0.008%, and a discontinuous grain growth temperature of 1350°C.

In addition, the obtained polycrystalline body was
The sample was cut into pieces with a size of m, and the heat treatment was performed in the same manner as in Example 1, and the change in porosity after the heat treatment was examined.

Example 3 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: fi 3.5%, rehydrated manganese: 22.5%,
A raw material powder mixture of S, 11 ferrite containing 14.0% zinc oxide was calcined in the air at a temperature of about 10°C for 2 hours, then crushed and formed into a predetermined shape. .

The obtained molded body was then fired in the next step. That is, 4J from room temperature to 8 fl O'c: If
i (with increasing temperature of 1 °C/hr, and 800 °C
The temperature was raised to 1000°C at a rate of 40°C/k+r, and the temperature was further maintained at 1000°C for 4 hours.

Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. vinegar! then 40”C/h
heating at 1200 °C gE with a heating rate of r, and 12
0 (By holding at a temperature of 1°C for 2 hours, the firing operation is continued and the matite phase in the compact is extinguished.)
Ta.

In addition, when we took out the fired body immediately after raising the temperature to 1100°C and the fired body after holding it at 1200°C for 2 hours, and examined the cut surface inside the fired body using X-ray diffraction, it was found that in the former, hematite phase remained. On the other hand, it was confirmed that the latter had 3011% ferrite Kankichi 2f, and the hematite phase disappeared between -. During this time, the firing atmosphere was
A nitrogen atmosphere with an oxygen concentration of 1% was used.

Then 1350° at a heating rate of 150°C/hr
The final firing operation was carried out by raising the temperature to a temperature of (:) and maintaining it at that temperature for 8 hours. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. After the firing, a cooling step of +1 (i 0°C or lower) was performed in a nitrogen atmosphere to obtain the desired fired ferrite body (polycrystalline body). This polycrystalline body had an average grain size of 10 .2 μm.

Porosity: 0.0118%, discontinuous grain growth temperature: 1420
It was ℃.

In addition, the obtained polycrystalline material was 5 am X 5 +n
Cut into pieces with a size of X 10III and heat-treated
The same method as in Example 1 was used to examine the change in porosity after the heat treatment.

Example 4 Ferrite raw material powder having a molar ratio of 65.0% ferric oxide, 25.0% manganese carbonate, and 10.0% zinc oxide obtained by roasting hydrothermally synthesized magnetite. The mixture was calcined in air at a temperature of about 1000° C. for 2 hours, then ground and molded into a predetermined shape.

The obtained molded body was then fired as follows.

That is, from room temperature to 800°C, the heating rate is 150°C/hr, and from 800°C to 1050°C, it is 40°C.
The temperature was increased at a temperature increase rate of /hr, and then the temperature was increased to 1050°C for 4 hours.
Holds time. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 3.0%. After that, 40
The hematite phase in the molded body was extinguished by increasing the temperature at a temperature increase rate of °C/hr and holding the temperature at 1220 °C for 2 hours. In addition, when we took out the fired body immediately after raising the temperature to 100°C and the fired body after holding it at 1220°C for 2 hours and examined the cut surface inside the fired body by X-ray diffraction, it was found that in the former, hematite phase remained. On the other hand, it was confirmed that the latter had a 100% ferrite phase, and the hematite phase had disappeared during this period. During this time, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1.0%.

A final calcination operation was then carried out by increasing the temperature to a temperature of 1350 °C at a heating rate of 150 °C/hr and holding at that temperature for 8 hours.

Also, during this firing, the firing atmosphere has an oxygen concentration of 1.0
% nitrogen atmosphere. After such firing, 11
A cooling step of 00° C. or lower was performed in a nitrogen atmosphere to obtain the desired fired ferrite body (polycrystalline body). This polycrystal has an average grain size of 9.2 μm and a porosity of 0.009%.
, discontinuous grain growth temperature: 1380°C.

In addition, the obtained polycrystalline material was divided into 5 am x 5 dragon x l
The sample was cut into a size of Os■, and then heat treated in the same manner as in Example 1, and the change in porosity after the heat treatment was examined.

Example 5 Ferrite raw material powder with a molar ratio of ferric oxide obtained by roasting hydrothermally synthesized magnetite: 66.5%, manganese carbonate: 17.0%, and zinc oxide: 16.5%. The mixture was calcined in air at a temperature of about 1000° C. for 2 hours, then ground and molded into a predetermined shape.

The obtained molded body was then fired as follows.

That is, from room temperature to 800°C, the heating rate is 150°C/hr, and from 800°C to 1000°C, it is 40°C.
The stomach was heated at a heating rate of / hr, and further heated to 1000°C (
It was held for 4 hours at IJ. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 10%. After that, the temperature was increased at a rate of 40°C/hr, and the temperature was increased to 120°C.
By holding the molded product at a temperature of 0° C. for 2 hours, the hematite I phase in the molded product disappeared. In addition, when we took out the fired body immediately after raising the temperature to 1100°C and the fired body after holding it at 1200°C for 2 hours and examined the cut surface inside the fired body by X-ray diffraction, it was found that the former had a hematite phase. In contrast, the latter is 100% ferrite phase,
During this time, it was confirmed that the hematite phase had disappeared.

During this time, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 3%.

Next, the final firing operation was carried out by heating to 1350°C at a heating rate of 150°C/hr and holding at that temperature for 8 hours. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 0.5%. and,
After such firing, a cooling step of 1100°C or lower is performed in a nitrogen atmosphere to obtain the desired ferrite fired body (polycrystalline body).
I got it. This polycrystalline material had an average grain size: io, 5 μm, a porosity: 0°008%, and a discontinuous grain growth temperature: 1410°C.

In addition, the obtained polycrystal was cut into a size of 5 fins x 5 cranes x 10 fins, and the heat treatment was performed in the same manner as in Example 1, and the change in porosity after the heat treatment was examined. .

Example 6 A ferrite raw material powder mixture having a molar ratio of 761.5% ferric oxide obtained by roasting hydrothermally synthesized magnetite, 20.5% manganese carbonate, and 12.0% zinc oxide. was calcined in air at a temperature of about 1000° C. for 2 hours, then ground and molded into a predetermined shape.

The obtained molded body was then fired as follows.

That is, from room temperature to 800°C, the heating rate is 150°C/hr, and from 800°C to 1100°C, it is 35°C.
The temperature was increased at a temperature increase rate of /hr, and the temperature was further maintained at 1100°C for 4 hours. The firing atmosphere during this firing was a nitrogen atmosphere with an oxygen concentration of 20%. Furthermore, after that,
The hematite phase in the molded body was eliminated by increasing the temperature at a rate of 35°C/hr and maintaining the temperature at 1250°C for 2 hours. In addition, when the fired body immediately after heating to 1,100°C and the fired body after being held at 1,250°C for 2 hours were taken out midway and the cut surface inside the fired body was examined by It was confirmed that while the hematite phase remained, the latter was 100% ferrite phase, and the hematite phase had disappeared during this time. During this time, the firing atmosphere is a nitrogen atmosphere with an oxygen concentration of 5%.

A final calcination operation was then carried out by raising the temperature to a temperature of 1370 °C at a heating rate of 150 °C/hr and holding at that temperature for 8 hours. Further, during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 0.3%. After the firing, a cooling step of 1100° C. or lower was performed in a nitrogen atmosphere to obtain the desired fired ferrite body (polycrystalline body).

This polycrystalline body has an average grain size: tO of 3 μm and a porosity of 20. 01%, discontinuous grain growth temperature: 1430°C.

In addition, this polycrystal was cut into a size of 5 dragons x 5 cranes x 10 m, and the heat treatment was performed in the same manner as in Example I, and the change in porosity after the heat treatment was examined.

Comparative Example 1 Ferrite raw material powder with a composition consisting of 0% ferric oxide obtained by roasting hydrothermally synthesized magnetite, 24.0% manganese carbonate, and 18.0% zinc oxide in molar ratio. The mixture was calcined in open air at a temperature of about 1000° C. for 2 hours, then pulverized and molded into a predetermined shape.

The obtained molded body was then fired as follows.

That is, from room temperature to 800°C, 150 T:/hr
and from 800℃ to 1000℃ at a heating rate of 4
Raise the temperature at a W-temperature rate of 0°C/hr, then 1000°C
The temperature was maintained for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 0.05%. After that, the temperature was increased at a rate of 40°C/hr, and 1
The temperature was kept at 200°C for 2 hours. In addition, when the fired body was removed from the middle immediately after the shoulder at 1100°C and the cut surface inside the fired body was examined by X-ray diffraction, it was found that it was 100% ferrite phase, and the hematite phase had already disappeared. I confirmed that it was. During this time, the firing atmosphere has an oxygen concentration of 0.
A 5% nitrogen atmosphere was used.

The final calcination operation was then carried out by increasing the temperature to a temperature of 1350 °C at a heating rate of 150 °C/hr and holding at that temperature for 8 hours. Furthermore, during this firing,
The firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 10%.

After the firing, a cooling step of 1100°C or lower is performed in a nitrogen atmosphere to obtain the desired ferrite fired body (
A polycrystalline substance) was obtained. This polycrystal has an average grain size of 10.
5 μm.

Porosity: O, O3%, discontinuous grain growth temperature: 1470°C
Met.

Further, this polycrystal was cut into a size of 5 mm x 5 m x 10 m, and the heat treatment was performed in the same manner as in Example 1, and the change in porosity after the heat treatment was examined.

Comparative Example 2 Ferrite raw material powder with a composition consisting of ferric oxide O, O% obtained by roasting hydrothermally synthesized magnetite, manganese carbonate: 15.0%, and zinc oxide: 15.0% in molar ratio. The mixture was calcined in air at a temperature of about 1000° C. for 2 hours, then ground and molded into a predetermined shape.

The obtained molded body was then fired as follows.

That is, from room temperature to 800°C, the heating rate is 150°C/hr, and from 800°C to 1000°C, it is 40°C.
The temperature was raised at a heating rate of /hr, and then maintained at a temperature of 1000°C for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 30%. After that, the temperature was increased at a rate of 40° (: / h r), and then ζ
The temperature was maintained at 1200°C for 2 hours. In addition, 1200℃
The fired body held for 2 hours was taken out midway through the process, and the cut surface inside the fired body was examined by X-ray diffraction, and it was confirmed that hematite phase remained and ferrite formation was not completed during this time. During this time, the atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%.

Next, Jl iG iG! at 150°C/hr. 13 degrees
A final calcination operation was carried out by increasing the temperature to 50° C. and holding at that temperature for 8 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 0.1%. After the firing, a cooling step of 1100° C. or lower was performed in a nitrogen atmosphere to obtain the desired fired ferrite body (polycrystalline body). This polycrystal has an average grain size of 10.3 μm.

Porosity: O, 5%, discontinuous grain growth temperature: 1460°C.

Further, this polycrystal was cut into a size of 5 mm x 5 mm x IQm, and the heat treatment was performed in the same manner as in Example 1, and the change in porosity after the heat treatment was examined.

Comparative Example 3 Ferrite raw material powder having a molar ratio of 52.5% ferric oxide obtained by roasting hydrothermally synthesized magnetite, 3t, O% manganese carbonate, and 16.5% zinc oxide. The mixture was calcined in air at a temperature of about 1000° C. for 2 hours, then ground and molded into a predetermined shape.

The obtained molded body was then fired as follows.

In other words, from room temperature to 800°C, the heating rate is 50°C/hr, and from 800°C to 1000°C, it is 40°C.
The temperature was increased at a temperature increase rate of /hr, and the temperature was further maintained at 1000°C for 4 hours. During this time, a vacuum atmosphere of 10-''torr or less was maintained.The fired body held at 1000°C for 4 hours was taken out midway, and the cut surface inside the fired body was examined by X-ray diffraction, and it was found that ferrite phase was 100%. It was confirmed that the hematite phase had already disappeared.Furthermore, the temperature was raised at a rate of 40°C/11r, and the temperature was maintained at 1200°C for 2 hours.

During this time, a vacuum atmosphere of 10 −3 Lorr or less was maintained.

A final firing operation was then performed by increasing the temperature to 1350°C at a heating rate of 150°C/hr and maintaining that temperature for 8 hours. Note that during this firing, the atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. and,
After the firing, a cooling step of 1100° C. or lower was performed in a nitrogen atmosphere to obtain the desired fired ferrite body (polycrystalline body).

This polycrystalline body has an average grain size of 8.5 μm, a porosity of 0,
008%, discontinuous grain growth temperature: 1420°C.

Further, this polycrystalline body was cut into a size of 5 mm x 5 w x 1 O x 1, and the heat treatment was performed in the same manner as in Example 1, and the change in porosity after the heat treatment was examined.

Comparative Example 4 Ferrai F. had a molar ratio of ferric oxide obtained by roasting hydrothermally synthesized magnetite: 63.5%, manganese carbonate: 22.5%, and zinc oxide: 14.0%. The raw material powder mixture was calcined in air at a temperature of about 1000° C. for 2 hours, then pulverized and molded into a predetermined shape.

The obtained molded body was then fired as follows.

That is, from room temperature to 800°C, the heating rate is 150°C/hr, and from 800°C to 1000°C, the heating rate is 40°.
Raise the temperature at a heating rate of C/br, then 1000°C
The temperature was maintained for 4 hours. And during that time, 10-3t
A vacuum atmosphere of orr or less was created. Furthermore, after that, 40℃/
hr heating rate, and at a temperature of 1200°C 2
Holds time. During this time, a vacuum atmosphere of 10-''torr or less was maintained.The fired body immediately after being heated to 1100° was taken out midway, and the cut surface inside the fired body was examined by X-ray diffraction. It becomes,
It was confirmed that the hematite phase had already disappeared.

Then, a final firing operation was performed in step 3, in which the temperature was raised to a temperature of 1350°C at a heating rate of 150°C/hr and held at that temperature for 8 hours. The firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. After the firing, a cooling step of 1100°C or higher is performed in a nitrogen atmosphere to obtain the desired fired ferrite (polycrystalline body).
I got it. This polycrystal has an average grain size of 9.8 μm and a porosity of 0.06%.

Discontinuous grain growth temperature: 1500°C.

Further, this polycrystal was cut into a size of 5 mm x 5 + u x 10 mm, and the heat treatment was performed in the same manner as in Example 1, and the change in porosity after the heat treatment was examined.

Comparative Example 5 The molar ratios were: ferric oxide obtained by roasting hydrothermally synthesized magnetite: 63.5%, manganese carbonate: 22.5%, zinc oxide: 14. A ferrite raw material powder mixture having a composition of 0% was calcined in air at a temperature of about 1000° C. for 2 hours, and then pulverized and molded into a predetermined shape.

The obtained molded body was heated at a temperature of 1200°C for 2 hours.
Preliminary firing was performed in a nitrogen atmosphere with an oxygen concentration of 10%. At this time, the temperature was raised and lowered at a rate of 300°C/hr, and a nitrogen atmosphere was used below 1100°C.

Next, the following HTTP processing was performed.

In order to prevent reduction, Mn--Zn ferrite powder having almost the same composition was filled around the pre-fired body, and the body was fired in the following manner using Ar gas as a pressure medium. Pressure crab 1000 kg/cd, temperature: 1300°C, treated for 2 hours, temperature rise and fall at this time was 300°C/hr,
Boosting again, V! The pressure was about 100°C. HI
After P, annealing treatment was performed under the same conditions as the pre-firing to obtain the desired ferrite sintered body.

Characteristics of various ferrite sintered bodies obtained in Examples 1 to 6 and Comparative Examples 1 to 5, namely porosity, 100e
The saturation magnetic flux density and porosity after heat treatment were investigated, and the results are shown in Table 1 below.

As is clear from the results in Table 1, the ferrite sintered bodies of Examples 1 to 6 according to the present invention have extremely high saturation magnetic flux densities, and all have porosity of 0.01% or less. Moreover, such porosity does not change even after heat treatment, and it is believed that there is no resuscitation of pores.

In contrast, 11S comparative example 1゜3 with a low mol% of iron oxide
The ferrite sintered body has a low saturation magnetic flux density, and when the mol% of iron oxide is increased, the porosity becomes high as in the ferrite sintered bodies of Comparative Examples 2 and 4.5, and the pores are revived by heating. It is observed that the porosity increases.

Table 1

Claims (6)

[Claims] (1) In molar ratio, 60-68% ferric oxide and 10-2
It has a composition of 0% zinc oxide and 30 to 12% manganese oxide, and has a saturation magnetic flux density (B_1_0) of 58
00G or more, porosity is 0.01% or less, and 1
A high-density ferrite characterized in that its porosity does not substantially increase during heat treatment at a temperature of 000°C or higher. (2) A method for producing high-density ferrite by firing a ferrite material containing 60 to 68 mol% of ferric oxide and having a hematite phase together with a ferrite phase, A first firing step of firing the hematite phase while gradually reducing it in an atmosphere with an oxygen concentration of 0.01 to 50%, and extinguishing the hematite phase in a temperature range of 1100 to 1250 °C, and extinguishing the hematite phase. The obtained ferrite material was heated to 1.
A method for producing high-density ferrite, comprising a second firing step of densifying the ferrite by firing at a temperature higher than 250°C. (3) the first firing step includes a multi-stage temperature raising step;
The final temperature raising step changes the ferrite material to 11
The method for producing high-density ferrite according to claim 2, wherein the hematite phase in the ferrite material is eliminated by heating to a temperature of 00 to 1250°C. (4) In the first firing step, the ferrite material is heated to a temperature of at least 800°C to reduce the hematite phase in the ferrite material. Manufacturing method of high-density ferrite. (5) The ferrite material has a molar ratio of 60 to 68%
of ferric oxide and 10-20% zinc oxide and 30-12%
The method for producing high-density ferrite according to any one of claims 2 to 4, which has a composition consisting of manganese oxide and manganese oxide. (6) The ferrite material has a molar ratio of 63 to 65%
of ferric oxide and 10-15% zinc oxide and 27-20%
of manganese oxide, and (the oxygen concentration in the firing atmosphere in the first firing step is 0.1 to 10%, and the oxygen concentration in the firing atmosphere in the second firing step is The method for producing high-density ferrite according to any one of claims 2 to 4, wherein the oxygen concentration is 1 to 20%.