JPH0440318B2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The present invention relates to a method for producing a single crystal ferrite body,
In particular, it relates to a method for producing a high magnetic flux density Mn-Zn single crystal ferrite body that can be suitably used for recording and reproducing heads for high coercivity magnetic recording media such as metal tapes and vapor-deposited tapes in VTRs, FDDs, RDDs, etc. It is. (Prior art and its problems) Ferrite materials such as Mn-Zn ferrite have traditionally been used as materials for magnetic recording/reproducing heads of VTRs and the like. From the viewpoint of wear resistance and workability of magnetic gaps, it is recommended to use a single crystal ferrite body. By the way, the ferrite material used as the magnetic head material generally has a composition containing 50 to 54% of ferric oxide in terms of molar ratio. Its saturation magnetic flux density B ₁₀
Since the value of ferrite is less than 5600G (Gauss), it could not be used as a ferrite for recording/reproducing heads of high coercivity magnetic recording media such as metal tapes. On the other hand, in JP-A No. 59-64599, in terms of molar ratio,
61.5-65% ferric oxide, 10-20% zinc oxide,
A method for producing single crystal ferrite bodies using the so-called Bridgmann process has been proposed, in which single crystal ferrite is grown from a melt (liquid phase) containing 28.5 to 15% manganese oxide. It has been shown that it is possible to obtain ferrites with a magnetic flux density B ₁₀ of 5500 G or more. However, when carrying out such a Bridziman method, it is necessary to use expensive equipment and a platinum crucible for melting the raw materials, which has the inherent problem that the resulting single crystal ferrite body is expensive. Moreover, since it is difficult to control the crystal orientation, there is a problem that when processing a single crystal ferrite body, the usable portion is reduced, resulting in a decrease in yield. In addition, the single crystal ferrite body produced by this Bridziman method is prone to compositional fluctuations due to scattering of raw materials during the manufacturing process, and due to differences in the coefficient of thermal expansion in the longitudinal direction of the single crystal body due to this. Therefore, cracks in the single crystal are likely to occur during cooling, and impurities such as platinum grains may be mixed in from the container (platinum crucible) used to melt the raw materials, resulting in uniform crystallinity of the single crystal. There are also inherent drawbacks. In addition, when producing a single crystal ferrite body with a ferric oxide content of more than 60 mol% as described above by a known single crystallization method using a solid phase reaction, the single crystal ferrite body that is the base material is used. When a ferrite raw powder mixture with a high proportion of ferric oxide is calcined in air to obtain a component (sintered body), the ferrite conversion rate is approximately 40 to 60%. When the calcined material is pulverized and the resulting molded body is fired using a normal vacuum firing method, the ferrite conversion rate is approximately 1000°C.
100%, that is, the hematite phase in the sintered body disappears, and therefore, even after subsequent sintering operations at temperatures of 1250°C or higher, it is not sufficiently densified, and the porosity of the obtained sintered body decreases. It was extremely difficult to reduce the amount to 0.01% or less. Moreover, since there are many pores in the resulting polycrystalline ferrite body, even if it were attempted to be single crystallized using a single crystallization method using a solid phase reaction, the temperature would be quite high, making it difficult to control single crystallization. In addition, there are inherent problems such as coarsening of crystal grains or generation of crystals with different orientations, and there is also the problem that a large amount of pores remain in the obtained ferrite single crystal. (Structure of the Invention) The present invention has been made against the background of the above, and its object is to provide a head for a high coercivity magnetic recording medium that has an extremely high saturation magnetic flux density _B10 . The purpose is to provide a single crystal ferrite body that can be suitably used for
Another objective is to provide a high-density single-crystal ferrite body that has extremely low porosity and does not impair the sliding properties of the magnetic head. The purpose of the present invention is to provide a low-cost method for manufacturing a single-crystal ferrite body with a low single-crystalization temperature, less generation of foreign species, no precipitates such as platinum grains, and a uniform composition. . In order to achieve such an object, the present invention provides ferrite monomers of the single crystal ferrite member by bringing the polycrystalline ferrite member and the single crystal ferrite member, at least a portion of which is a single crystal, into contact with each other and heating the member. When crystals are grown on the polycrystalline ferrite member side to grow a ferrite single crystal and form a single crystal ferrite body, the polycrystalline ferrite member (a) contains 60 to 68 mol% of ferric oxide. A ferrite material containing a hematite phase together with a ferrite phase is fired in an atmosphere with an oxygen concentration of 0.01 to 50% while gradually reducing the hematite phase, and the hematite phase is removed in a temperature range of 1100 to 1250°C. (b) a first firing step to extinguish the
The ferrite material in which the hematite phase has been eliminated is fired at a temperature higher than 1250°C in an atmosphere with an oxygen concentration of 0.1 to 100% to densify it. It is characterized by using a polycrystalline ferrite body. In particular, from 60 to 68% ferric oxide, 10 to 20% zinc oxide, and 30 to 12% manganese oxide in molar ratio, obtained according to the method for producing such a single crystal ferrite body. A single _- crystal ferrite body having a composition of It can be suitably used as a magnetic head, and can also be suitably used as a ferrite material that does not impair the sliding characteristics of a magnetic head. Incidentally, the first firing step in the above-described method for manufacturing a single crystal ferrite body according to the present invention generally includes a plurality of temperature raising steps, and the final temperature raising step brings the ferrite material to a temperature of 1100 to
It will be heated to a temperature of 1250° C. so that the hematite phase in the ferrite material can be substantially eliminated. In addition, in the first firing step, the ferrite material is usually at least
It is heated to a temperature of 800°C to reduce the hematite phase in the ferrite material. Further, according to a preferred embodiment of the present invention, the ferrite material has a composition consisting of 63 to 65% ferric oxide, 10 to 15% zinc oxide, and 27 to 20% manganese oxide in molar ratio. 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 1 to 20%. becomes. (Specific explanation and effects of the structure) By the way, the ferrite material used to form the polycrystalline ferrite body in the present invention contains ferric oxide (Fe ₂ O ₃ ) in a proportion of 60 to 68 mol%. A ferrite raw powder mixture having such a composition is calcined in accordance with a conventional method, and then pulverized, and a molded body is formed into a suitable shape such as a block. It will be used as the ferrite material. In addition, such molded bodies generally have a weight of 40
About 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. Furthermore, the composition of such a ferrite material is that of a polycrystalline ferrite body obtained by firing it as it is, and furthermore, a composition of a single-crystalline ferrite body, which is the final object. A single crystal ferrite body with a saturation magnetic flux density of B ₁₀ is
Generally, in molar ratio, 60-68% ferric oxide ( _Fe2O3 ), 10-20% zinc oxide ( _ZnO ) and 30-68% ferric oxide (Fe2O3),
Obtained using a ferrite material with a composition consisting of 12% manganese oxide (MnO), especially 63-65 mol% ferric oxide, 10-15 mol% zinc oxide, and 27-20 mol% manganese oxide. A ferrite material with a composition of The ferrite material (calcined product molded body) having a hematite phase together with such a ferrite phase is
First, the ferrite material is fired in an atmosphere of He, Ar, _N2 , etc. with an oxygen concentration of 0.01 to 50% to gradually reduce the hematite phase in the ferrite material, and then the ferrite material is fired in a temperature range of 1100 to 1250°C. The hematite phase is substantially eliminated (first firing step). In other words, in this first firing step, the temperature and oxygen partial pressure (concentration ) will be adjusted. Note that if the oxygen concentration in the firing atmosphere is lower than 0.01%, the ferrite material will progress quickly and the hematite phase will virtually disappear in the low temperature range, so the porosity of the ferrite material must be maintained sufficiently. Furthermore, when the oxygen concentration exceeds 50%, the progress of ferrite formation is slow, and the disappearance of the hematite phase is delayed until the second firing process, leaving coarse pores inside the sintered body. There is a problem that is getting worse. In particular, the preferred
The composition range of Mn-Zn ferrite material is from 0.1 to
A firing atmosphere with an oxygen concentration of 10% is used. Furthermore, if the hematite phase substantially disappears at a temperature below 1100°C, the ferrite material cannot be sufficiently densified in the second firing step, and the porosity of the final fired product will be sufficiently reduced. This becomes difficult. Furthermore, the disappearance of the hematite phase
If it is carried out at a temperature of 1250° C. or higher, there is a problem that coarse pores will be formed in the subsequent second firing step. Furthermore, as the firing temperature of the ferrite material in this first firing step, a temperature of 800°C or higher is generally used. 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 such a first firing step, a method is adopted in which the ferrite material is fired using a temperature raising operation in which the temperature is raised stepwise or continuously. The firing temperature is increased step by step according to the stage temperature raising process, and in the final temperature raising process, the ferrite material 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; This is followed by a first holding step consisting of holding the reached temperature for a predetermined time, followed by a second temperature raising step of raising the temperature to a predetermined temperature within the range of 1100 to 1250°C, and then holding the reached temperature for a predetermined time. and a second holding step of substantially eliminating the hematite phase. The temperature increase speed at that time is usually 150 to 800℃.
The heating rate will be approximately 200°C/hr, and the heating rate will be approximately 30 to 40°C/hr in both the first and second temperature raising steps. Next, the ferrite material whose hematite phase has been eliminated in the first firing step is
Furthermore, it is fired in a second firing step to further densify it. The firing atmosphere in this second firing step is 0.1 to 100%
In particular, in the preferred composition range of the Mn-Zn ferrite material, an atmosphere having an oxygen concentration of 1 to 20% is used. This is necessary for controlling the crystal grain size and magnetic properties of ferrite. In addition,
Components other than oxygen in this firing atmosphere are He, Ar
It is an inert gas component such as or _N2 . In addition, it is necessary to use a firing temperature of over 1250°C, which allows effective sintering to proceed, thereby obtaining a dense ferrite sintered body with an effective reduction in porosity. It is possible. The sintered body of the ferrite material obtained through the first firing step and the second firing step according to the present invention, in other words, the polycrystalline ferrite body, generally has a maximum crystal grain size of about 40 μm, It is a material with a dense polycrystalline structure, usually as fine as about 10 μm, and with a porosity of about 0.01% or less. Due to the presence of the ferrite single crystal in the contacting single-crystalline ferrite member, the ferrite single crystal is grown toward the polycrystalline ferrite body, and the ferrite single crystal is grown to a large size, thereby producing the desired single-crystal ferrite body. . As is well known, the polycrystalline ferrite body formed into a single crystal in this manner is generally considered to be a polycrystalline body of ferrite that causes discontinuous crystal grain growth at high temperatures. More specifically, polycrystalline materials exhibiting discontinuous crystal grain growth are characterized by the fact that when the heating temperature reaches a certain temperature,
Some crystal grains suddenly coalesce with the surrounding fine crystal grains and grow into huge crystal grains at an extremely faster growth rate than the growth rate of the surrounding fine grains. As a raw material for iron oxide, which is one of the main components, iron oxide with a spinel structure or iron oxide with a spinel history,
Or a mixture thereof using iron oxide containing at least 60% by weight in terms of Fe ₂ O ₃ ,
It is advantageously formed. On the other hand, at least a portion of the single crystal ferrite member, which is a seed single crystal for single crystallizing such a polycrystalline ferrite body (polycrystal ferrite member), is a single crystal. In other words, it is a ferrite material having at least a portion of single crystal ferrite,
Moreover, it is important to use a polycrystalline ferrite member having the same or similar composition to the polycrystalline ferrite member, and by using such a single-crystalline ferrite member, the ferrite single crystal portion present therein is removed. Single crystals begin to grow toward the polycrystalline ferrite member. Of course, there is no problem even if the entire single crystal ferrite member is made of one single crystal, but from an economic point of view, it is better to use a polycrystalline ferrite member that partially has a single crystal ferrite portion. Preferably, it is a single crystal composite ferrite. When using such a single crystal ferrite member and bringing it into contact with a polycrystalline ferrite member as a seed crystal to join them,
It is desirable that the ferrite single crystal portion of such a single crystal ferrite member is brought into contact with the polycrystalline ferrite member. In other words, the crystal plane of the ferrite single crystal of the single-crystalline ferrite member is exposed as a contact surface (joint surface) and brought into contact with a predetermined contact surface (joint surface) of the polycrystalline ferrite member. It is. The contact surfaces of the single-crystalline ferrite member and the polycrystalline ferrite member must be sufficiently mirror-polished prior to their contact in order to ensure close contact with each other. In addition, for contact caused by butting two ferrite members, it is possible to temporarily bond the ferrite members by interposing an acid that dissolves ferrite, such as hydrochloric acid, nitric acid, or sulfuric acid, in the abutting portion of the two ferrite members. desirable. The reason for this is that the mutual positions of the monocrystalline ferrite member and the polycrystalline ferrite member are fixed with salts of ferrite components formed by such acids, such as iron nitrate, manganese nitrate, zinc nitrate, etc. This is because, during subsequent heating, the oxides produced by decomposition of such salts are effective in promoting the desired solid phase reaction. In addition to the above-mentioned acids, an aqueous solution of an inorganic acid salt containing a ferrite component can also be effectively used to bond the two ferrite members when they are brought together, and the same effect can be obtained. Next, by heating the single-crystalline ferrite member and the polycrystalline ferrite member while in contact with each other in this manner, the ferrite members are directly joined integrally by a solid phase reaction,
Thereafter, the polycrystalline ferrite member is single crystallized, and such integral joining and single crystallization of the polycrystalline ferrite member are performed simultaneously and continuously. First, since sintering of ferrite by solid phase reaction proceeds at a temperature of approximately 1100°C, it is possible to directly Integral bonding requires heating to a temperature of 1100°C or higher. Further, in the single crystallization operation performed subsequent to bonding by solid phase reaction, the temperature at which the ferrite single crystal grows toward the polycrystalline ferrite member is lower than the temperature at which discontinuous grain growth occurs in the polycrystalline ferrite member. Therefore, by heating the above-mentioned joined body at a temperature somewhat lower than the discontinuous grain growth temperature, the ferrite single crystal of the single-crystalline ferrite member can be grown toward the polycrystalline ferrite member. By growing a ferrite single crystal, it is possible to convert a large portion or the entire polycrystalline ferrite member into a single crystal. Incidentally, heating for performing the solid phase reaction and single crystallization of the combination (temporary bond) of a single crystal ferrite member and a polycrystalline ferrite member is generally performed in a heating furnace. The atmosphere inside this heating furnace is important in maintaining the properties of ferrite, and care must be taken. This is because the properties of ferrite are significantly deteriorated by exposure, oxidation, or reduction.
Therefore, it is important to create an atmosphere with so-called equilibrium oxygen partial pressure, in which the oxygen partial pressure is balanced with that of ferrite.
However, controlling this oxygen partial pressure is extremely difficult, and therefore, generally, a simple and easily adopted method is to place the combination of ferrite members in a ceramic sagger such as alumina and heat it. be. In addition, the combination of ferrite members is placed in a sagger made of ceramics such as alumina, and the same ferrite member powder or ferrite plate as the ferrite members to be joined is used as a dummy material for atmosphere adjustment. It is preferable to keep it in. This is because such a ferrite material as a dummy material releases or absorbs oxygen during heating, and has the effect of adjusting the excess or deficiency of oxygen in the sagger. The single-crystal ferrite body thus obtained, that is, the single-crystalline product of the single-crystal ferrite member-polycrystal ferrite member assembly, has a homogeneous composition, and therefore stable magnetic properties, and is suitable for Bridgeman. It has the characteristic that there are no precipitates such as platinum grains that are found in single crystal bodies obtained by the method, and the polycrystalline ferrite member as the base material is produced by the pressureless sintering method. In addition, it is cheaper than other methods, does not require large equipment, and is a simple process. Furthermore, the composition of the single crystal ferrite body obtained according to the present invention is changed to 60 to 68 mol% of ferric oxide and 10 to 68 mol% of ferric oxide.
The saturation magnetic flux density B ₁₀ can be increased to 5800G by using an Mn-Zn ferrite composition consisting of 20 mol% acid zinc oxide and 30 to 12 mol% manganese oxide.
As described above, a single crystal ferrite body of preferably 6000G or more can be obtained, which is suitable for recording and recording magnetic recording media such as metal tapes and vapor-deposited tapes with high coercivity.
It can be advantageously used as a head material for regeneration. Note that the porosity in the present invention is expressed as a percentage of the area occupied by pores in an arbitrary cut surface of a sample, and is specifically determined as follows. That is, an arbitrary cut surface of a given sample is polished, and the polished surface is inspected at 1000x magnification using a metallurgical microscope to determine the diameter of pores in the field of view: d and the number of pores: n. is measured, the porosity is measured from the pore area with respect to the total visual field area, and the porosity: P% is determined according to the following formula. P (%) = 〓 ⁱ π (d _i /2 ² n _i /measurement area x 100, where d _i : pore diameter (length) n _i : number of pores with pore diameter d _i In addition, the ferrite conversion rate in the present invention and indicates the weight percent of the ferrite phase, and was calculated by measuring the weight of the hematite phase at the time of preparation and the weight of the hematite phase after calcination, and assuming that all the disappeared hematite had become the ferrite phase. Furthermore, the saturation magnetic flux density B ₁₀ indicates the saturation magnetic flux density in a magnetic field of 10 Oe. (Examples) In order to clarify the present invention more specifically, some examples of the present invention will be described below. However, it goes without saying that the present invention shall not be construed in any way limited by the description of such examples. In addition to the following examples, the present invention can be implemented in various embodiments, and the present invention can be implemented in various embodiments based on the knowledge of those skilled in the art, as long as it does not depart from the spirit of the present invention. Example 1 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 61.0%, manganese carbonate: 27.0%,
A ferrite raw material powder mixture having a composition of 12.0% zinc oxide 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held at 1000°C for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 0.1%. Then 40℃/hr
The first firing operation was continued by raising the temperature at a temperature increase rate of 1200°C and holding it for 2 hours to eliminate the hematite phase in the molded body. 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 in the former, hematite phase remained. In contrast, in the latter case, it was 100% ferrite phase, and it was confirmed that the hematite phase had disappeared during this time. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. Thereafter, the temperature was increased to 1300°C at a rate of 150°C/hr, and the temperature was maintained for 8 hours to perform a second firing operation. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 5%. 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 ferrite member). The obtained polycrystalline ferrite member 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, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this joined body is heated for 3 hours at 1320°C, which is lower than 1340°C, which is the discontinuous grain growth temperature of the polycrystalline structure of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid-phase reaction, the entire bonded body became a single ferrite single crystal, and its porosity was 0.01%. Example 2 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 62.5%, manganese carbonate: 26.5%,
A ferrite raw powder mixture having a composition of 11.0% 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃ at a heating rate of 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held 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 40℃/hr
The first firing operation was continued by raising the temperature at a temperature increase rate of 1220°C and holding it for 2 hours to eliminate the hematite phase in the molded body. 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 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. In contrast, in the latter case, it was 100% ferrite phase, and it was confirmed that the hematite phase had disappeared during this time. Further, during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. Thereafter, the temperature was increased to 1300° C. at a rate of 150° C./hr and maintained at that temperature for 8 hours to carry out a second firing operation. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 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 ferrite member). The obtained polycrystalline ferrite member 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, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this joined body is heated for 3 hours at 1330°C, which is lower than 1350°C, which is the discontinuous grain growth temperature of the polycrystalline composition of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid-phase reaction, the entire bonded body became a single ferrite single crystal, and its porosity was 0.08%. Example 3 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 63.5%, manganese carbonate: 22.5%,
A ferrite raw powder mixture having a composition of 14.0% zinc oxide 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held at 1000°C for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. Next, the first firing operation was continued by raising the temperature at a rate of 40° C./hr and holding it at 1200° C. for 2 hours to eliminate the hematite phase in the compact. 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 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. In contrast, in the latter case, it was 100% ferrite phase, and it was confirmed that the hematite phase had disappeared during this time. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. Thereafter, the temperature was increased to 1350°C at a rate of 150°C/hr, and the temperature was maintained for 8 hours to carry out a second firing operation. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 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 ferrite member). The obtained polycrystalline ferrite member had an average grain size of 10.2 μm, a porosity of 0.008%, and a discontinuous grain growth temperature of 1420°C. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this joined body is heated for 3 hours at 1400°C, which is lower than 1420°C, which is the discontinuous grain growth temperature of the polycrystalline composition of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid phase reaction, the entire bonded body becomes a single ferrite single crystal, and its porosity is 0.008%.
It was hot. Example 4 In molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 65.0%, manganese carbonate: 25.0%,
A ferrite raw material powder mixture having a composition of zinc oxide: 10.0% 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1050°C at a rate of 40°C/hr, and then held at 1050°C for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 3%. Next, the first firing operation was continued by raising the temperature at a rate of 40° C./hr and holding it at 1220° C. for 2 hours to eliminate the hematite phase in the compact. 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 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. In contrast, in the latter case, it was 100% ferrite phase, and it was confirmed that the hematite phase had disappeared during this time. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 1%. Thereafter, the temperature was increased to 1350°C at a rate of 150°C/hr, and the temperature was maintained for 8 hours to carry out a second firing operation. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 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 ferrite member). The obtained polycrystalline ferrite member had an average grain size of 9.2 μm, a porosity of 0.009%, and a discontinuous grain growth temperature of 1380°C. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this bonded body is heated for 3 hours at 1360°C from 1380°C, which is the discontinuous grain growth temperature of the polycrystalline structure of the polycrystalline ferrite member, to induce a solid phase reaction, and the single crystal structure of the polycrystalline ferrite member is Crystallization proceeded. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere at temperatures below 1100°C, and a nitrogen atmosphere with an oxygen concentration of 5% above 1100°C. Through this solid-phase reaction, the entire bonded body became a single ferrite single crystal, and its porosity was 0.01%. Example 5 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 66.5%, manganese carbonate: 17.0%,
A ferrite raw powder mixture having a composition of 16.5% zinc oxide 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held at 1000°C for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 10%. Next, the first firing operation was continued by raising the temperature at a rate of 40° C./hr and holding it at 1200° C. for 2 hours to eliminate the hematite phase in the compact. 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 in the former, hematite phase remained. In contrast, in the latter case, it was 100% ferrite phase, and it was confirmed that the hematite phase had disappeared during this time. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 3%. Thereafter, the temperature was increased to 1350°C at a rate of 150°C/hr, and the temperature was maintained for 8 hours to carry out a second firing operation. During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 0.5%. 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 ferrite member). The obtained polycrystalline ferrite member had an average grain size of 10.5 μm, a porosity of 0.008%, and a discontinuous grain growth temperature of 1410°C. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this bonded body is heated for 3 hours at 1390°C, which is lower than 1410°C, which is the discontinuous grain growth temperature of the polycrystalline structure of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member is heated. Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid phase reaction, the entire bonded body becomes a single ferrite single crystal, and its porosity is 0.008%.
It was hot. Example 6 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 67.5%, manganese carbonate: 20.5%,
A ferrite raw material powder mixture having a composition of 12.0% zinc oxide 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃ at a heating rate of 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 35°C/hr, and then held at 1100°C for 4 hours. Note that during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 20%. Next, the first firing operation was continued by increasing the temperature at a rate of 35° C./hr and holding it at 1250° C. for 2 hours to eliminate the hematite phase in the compact. 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 1250°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. In contrast, in the latter case, it was 100% ferrite phase, and it was confirmed that the hematite phase had disappeared during this time. Further, during this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 5%. Thereafter, the temperature was increased to 1370° C. at a rate of 150° C./hr and maintained at that temperature for 8 hours to carry out a second firing operation. 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 ferrite member). The obtained polycrystalline ferrite member had an average grain size of 10.3 μm, a porosity of 0.01%, and a discontinuous grain growth temperature of 1430°C. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this joined body is heated for 3 hours at 1400°C, which is lower than 1430°C, which is the discontinuous grain growth temperature of the polycrystalline structure of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid-phase reaction, the entire bonded body became a single ferrite single crystal, and its porosity was 0.01%. Comparative Example 1 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 58.0%, manganese carbonate: 24.0%,
A ferrite raw powder mixture having a composition of 18.0% zinc oxide 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held at 1000°C for 4 hours. During this firing, the firing atmosphere has an oxygen concentration of 0.05.
% nitrogen atmosphere. Thereafter, the temperature was increased at a rate of 40° C./hr, and the temperature was maintained at 1200° C. for 2 hours. In addition, when we took out the fired body immediately after raising the temperature to 1100℃ and examined the cut surface inside the fired body by X-ray diffraction method, we found that it was 100% ferrite phase, and the hematite phase had already disappeared. It was confirmed. During this time, the oxygen concentration in the firing atmosphere is
A 0.5% nitrogen atmosphere was used. The final firing operation was then carried out by raising the temperature to 1300°C at a temperature increase 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 10%. 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 ferrite member). This obtained polycrystalline ferrite member has an average grain size:
10.5μm, porosity: 0.03%, discontinuous grain growth temperature:
It was 1470℃. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this joined body is heated for 3 hours at 1450°C, which is lower than 1470°C, which is the discontinuous grain growth temperature of the polycrystalline structure of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid-phase reaction, the entire bonded body became a single ferrite single crystal, and its porosity was 0.03%. Comparative Example 2 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 70.0%, manganese carbonate: 15.0%,
A ferrite raw material powder mixture having a composition of zinc oxide: 15.0% 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held at 1000°C for 4 hours. During this firing, the firing atmosphere has an oxygen concentration of 30%.
A nitrogen atmosphere was set. Thereafter, the temperature was increased at a rate of 40° C./hr, and the temperature was maintained at 1200° C. for 2 hours. In addition, when the fired body kept at 1200℃ for 2 hours was taken out midway and the cut surface inside the fired body was examined by X-ray diffraction, it was confirmed that hematite phase remained and that ferrite formation was not completed during this time. . During this firing, the firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 5%. The final firing operation was then carried out by raising the temperature to 1300°C at a temperature increase rate of 150°C/hr and maintaining that temperature for 8 hours. Further, 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 ferrite member). The obtained polycrystalline ferrite member had an average grain size of 10.3 μm, a porosity of 0.05%, and a discontinuous grain growth temperature of 1460°C. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to a size of 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this bonded body is heated for 3 hours at 1430°C from 1460°C, which is the discontinuous grain growth temperature of the polycrystalline composition of the polycrystalline ferrite member, to induce a solid phase reaction and to cause the single grain growth temperature of the polycrystalline ferrite member. Crystallization proceeded. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere at temperatures below 1100°C, and a nitrogen atmosphere with an oxygen concentration of 5% above 1100°C. Through this solid-phase reaction, the entire bonded body became a single ferrite single crystal, and its porosity was 0.05%. Comparative Example 3 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 52.5%, manganese carbonate: 31.0%,
A ferrite raw powder mixture having a composition of 16.5% zinc oxide 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held at 1000°C for 4 hours, during which time a vacuum atmosphere of 10 ^-3 torr or less was maintained. Furthermore, this
When the fired body was fired for 4 hours at 1000°C, it was taken out halfway through, and the cut surface inside the fired body was examined by X-ray diffraction, and it was confirmed that it was 100% ferrite phase, and that the hematite phase had already disappeared. did. After that, the temperature was further increased at 40℃/hr, and the temperature was increased to 1200℃ for 2 hours.
It was held for a period of time, during which time a vacuum atmosphere of 10 ^-3 torr or less was created. Next, the temperature was raised to 1300°C at a heating rate of 150°C/hr, and the temperature was maintained for 8 hours to carry out the final firing operation. Also, during this firing,
The firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 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 ferrite member). This obtained polycrystalline ferrite member has an average grain size:
8.5μm, porosity: 0.008%, discontinuous grain growth temperature:
It was 1420℃. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this joined body is heated for 3 hours at 1350°C, which is lower than 1370°C, which is the discontinuous grain growth temperature of the polycrystalline structure of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member is heated. Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid phase reaction, the entire bonded body becomes a single ferrite single crystal, and its porosity is 0.008%.
It was hot. Comparative Example 4 In terms of molar ratio, ferric oxide obtained by roasting hydrothermally synthesized magnetite: 63.5%, manganese carbonate: 22.5%,
A ferrite raw powder mixture having a composition of 14.0% zinc oxide 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 (ferrite material) was then fired as follows. That is, first, from room temperature to 800℃, the heating rate was 150℃/hr, and then
The temperature was raised from 800°C to 1000°C at a rate of 40°C/hr, and then held at 1000°C for 4 hours, during which time a vacuum atmosphere of 10 ^-3 torr or less was maintained. After that, the temperature was further increased at 40℃/hr, and the temperature was increased to 1200℃ for 2 hours.
It was held for a period of time, during which time a vacuum atmosphere of 10 ^-3 torr or less was created. In addition, when the fired body kept at 1000℃ for 4 hours was taken out midway and the cut surface inside the fired body was examined by X-ray diffraction, it was found to be 100% ferrite phase, and the hematite phase had already disappeared. It was confirmed. Next, the temperature was raised to 1300°C at a heating rate of 150°C/hr, and the temperature was maintained for 8 hours to carry out the final firing operation. Also, during this firing,
The firing atmosphere was a nitrogen atmosphere with an oxygen concentration of 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 ferrite member). This obtained polycrystalline ferrite member has an average grain size:
9.8μm, porosity: 0.06%, discontinuous grain growth temperature:
It was 1500℃. In addition, this obtained polycrystalline ferrite member,
It was cut to a size of 5 mm x 10 mm x 20 mm, and one side was polished to a smoothness R _nax : 0.05 μm, while the 111 side of a single crystal ferrite member with the same composition was cut to 5 mm x 10 mm.
A piece measuring 2 mm in size was polished in the same manner, and the polished surfaces (surfaces in 5 mm x 10 mm size) were bonded together using a 1N nitric acid aqueous solution. Next, this bonded body is heated for 3 hours at 1480°C, which is lower than 1500°C, which is the discontinuous grain growth temperature of the polycrystalline structure of the polycrystalline ferrite member, to induce a solid phase reaction, and the polycrystalline ferrite member Single crystallization progressed. The temperature was raised and lowered at a rate of 300°C/hr, and the reaction atmosphere was a nitrogen atmosphere below 1100°C;
In the above, a nitrogen atmosphere with an oxygen concentration of 5% was used. Through this solid-phase reaction, the entire bonded body became a single ferrite single crystal, and its porosity was 0.06%. 【table】

Claims (1)

[Scope of Claims] 1. By bringing a polycrystalline ferrite member and a single-crystalline ferrite member, at least a portion of which is a single crystal, into contact and heating, the ferrite single crystal of the single-crystalline ferrite member is converted into the polycrystalline ferrite member. When growing a ferrite single crystal by crystal growth on the member side to form a single crystal ferrite body, the polycrystalline ferrite member contains (a) ferric oxide in a proportion of 60 to 68 mol%, and ferrite A ferrite material having a hematite phase as well as a hematite phase is fired in an atmosphere with an oxygen concentration of 0.01 to 50% while gradually reducing the hematite phase,
and (b) the ferrite material from which the hematite phase has been removed is heated in an atmosphere with an oxygen concentration of 0.1 to 100%. , a second firing step of densifying the polycrystalline ferrite body by firing it at a temperature higher than 1250°C. 2. The first firing step includes multiple temperature raising steps, and in the final temperature raising step, the ferrite material is heated to a temperature of 1100 to 1250°C, and the hematite phase in the ferrite material disappears. A method for producing a single crystal ferrite body according to claim 1. 3. The single crystal according to claim 1 or 2, wherein 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. Method for manufacturing ferrite bodies. 4 The ferrite material has a molar ratio of 60 to 68%
The single crystal ferrite according to any one of claims 1 to 3, which has a composition of ferric oxide, 10 to 20% zinc oxide, and 30 to 12% manganese oxide. How the body is manufactured. 5 The ferrite material has a molar ratio of 63 to 65%
of ferric oxide, 10 to 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%. Claims 1 to 3, wherein the oxygen concentration in the firing atmosphere in the second firing step is 1 to 20%.
A method for producing a single-crystal ferrite body according to any one of paragraphs.