CA1073658A - Method of manufacturing a manganese-zinc-ferro-ferrite core, in particular for use in magnetic heads - Google Patents
Method of manufacturing a manganese-zinc-ferro-ferrite core, in particular for use in magnetic headsInfo
- Publication number
- CA1073658A CA1073658A CA239,375A CA239375A CA1073658A CA 1073658 A CA1073658 A CA 1073658A CA 239375 A CA239375 A CA 239375A CA 1073658 A CA1073658 A CA 1073658A
- Authority
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- Canada
- Prior art keywords
- temperature
- mixture
- prefiring
- sintering
- zinc
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
- C04B35/2658—Other ferrites containing manganese or zinc, e.g. Mn-Zn ferrites
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/133—Structure or manufacture of heads, e.g. inductive with cores composed of particles, e.g. with dust cores, with ferrite cores with cores composed of isolated magnetic particles
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Magnetic Ceramics (AREA)
- Soft Magnetic Materials (AREA)
- Magnetic Heads (AREA)
Abstract
ABSTRACT:
An improvement of the method of sintering Mn-Zn ferrites. In order to realize a very high density and an associated large resistance to detrition, the ferrite powders used, prior to sintering, are reduced to their stoichiometric spinel composition as much as possible and measures are taken to prevent oxidation during heating to the sintering temperature and cooling after the sintering.
An improvement of the method of sintering Mn-Zn ferrites. In order to realize a very high density and an associated large resistance to detrition, the ferrite powders used, prior to sintering, are reduced to their stoichiometric spinel composition as much as possible and measures are taken to prevent oxidation during heating to the sintering temperature and cooling after the sintering.
Description
~L~736S~3 PHN 7819 The invention relates to a method of manufacturing a manganese-zinc-ferro-ferrite core having a low porosity, in particular for use in magnetic heads, and comprising the fol-lowing steps:
preparing a mixture containing oxides o~ iron, manganese and zinc or products which provide said oxides dur;ng one of the followin~ process steps, prefiring said mixture;
grinding the prefired material~
compressing the ground material;
heating the compressed material to the sintering temperature;
and the sintering thereof.
Of late, ferrites, in particular manganese-zinc ferrites, have been used on a large scale in the magnetic heads of magnetic recording and reproducing apparatus, for example, audio and video tape recording apparatus, said materials have displaced metal alloys such as Ni-Fe and Al-Fe-Si.
The use of ferrites as a magnetic core material for magnetic heads is to be preferred on the basis of the fact that ferrites readily withstand detrition, have excellent magnetic properties as regards saturation magnetisation, coercive force and permeability, and moreover have excellent characteristics at high frequencies. In this connection there should be distinguished between manganese-zinc ferrites
preparing a mixture containing oxides o~ iron, manganese and zinc or products which provide said oxides dur;ng one of the followin~ process steps, prefiring said mixture;
grinding the prefired material~
compressing the ground material;
heating the compressed material to the sintering temperature;
and the sintering thereof.
Of late, ferrites, in particular manganese-zinc ferrites, have been used on a large scale in the magnetic heads of magnetic recording and reproducing apparatus, for example, audio and video tape recording apparatus, said materials have displaced metal alloys such as Ni-Fe and Al-Fe-Si.
The use of ferrites as a magnetic core material for magnetic heads is to be preferred on the basis of the fact that ferrites readily withstand detrition, have excellent magnetic properties as regards saturation magnetisation, coercive force and permeability, and moreover have excellent characteristics at high frequencies. In this connection there should be distinguished between manganese-zinc ferrites
- 2 -~.~
. ~, , ~L~73tj58 PHN 7~19 which have the better magnetic properties and nickel-zinc ferrites which can better withstand detrition. Good detrition properties are of importance in particular when the ferrite heads are used in contact with a high-speed magnetic tape, for example, in video applications. In this connection the porosity of the ferrites plays an important role. For certain applications, for example in video heads, a porosity of the core material is required which may no~exceed a few tenths of a percent. It has so far not been possible to manufacture maganese-zinc-ferro-ferrite cores having such a low porosity via the usual processes. Although a porosity of 0.6% is obtainable, this low porosity was obtained by leading over the ferrite a reducing gas-containing hydrogen during the heating prior to sintering. It should be noted that this process is difficult to control because as a result of exceedingly far redùction other oxidic phases or even metallic phases can easily be formed, so that the composition of the resulting material cannot be readily controlled.
It is the object of the invention to provide a method of the kind mentioned in the preamble with which it is possible to manufacture manganese-zinc-ferro-ferrite cores hav~ng a minimum porosity and a high resistance to detrition.
It has been found that a manganese-zinc-ferrite core which satisfies said requirements can be manufactured if, according to the invention, during one of the steps preceding the sintering, the material to be sintered is given the stoichiometric spinel composition as much as possible.
This is to be understood to mean that in the formula which ~ 1) .~ .;
.
~37 3t;5 ~3 PHN 7819 represents the composition the ratio oF the anions to the cations should approach the ratio 3:4 as much as possible.
In the conventional method of manufacturing manganese-zinc-ferro ferrite cores the starting powders are -prefired in air or nitrogen at temperatures between 800 and 1000C for at most a few hours. The starting powders com-prise an excess of oxygen already prior to the prefiring treatment since the iron component and sometimes also the manganese component is weighed-in in the form of the ~ri-valent ion, that is to say Fe203 and Mn203, respectively~
Also the prefired powders, even those prefired in nitrogen, still contain a considerable excess of oxygen, in other words, they do not have the stoichiometric spinel com-position. They are reduced to said composition only during sintering. Investigations performed by Applicants have proved that in course of things forms an ohstruction for obtaining a low porosity. However, when the material has the stoichiometric spinel composition already at the instant at which it will be sintered, low values of the porosity prove to be realisable indeed.
It is possible within the scope of the invention to reduce a prefired powder which ~oes not have the stoichiomekr~c spinel composition to said compositlon dur~ng heating to the sintering temperature. A problem involved is, however, that it is difficult to reduce the powder integrally in that stagei since it has been compressed to a desired shape at a considerably high pressure ~for example, 1000 kg/sq.cm), the oxygen upon reducing diffuses only slowly from the interior to the exterior.
- - -~'73658 A preferred embodiment of the method according to the invention is therefore characterized in that the material is given the stoichiometric spinel composition as much as possible during the prefiring step. In order to realize this, several reduction methods may be used, for example, the required Fe2 in the form of Fe304 may be added prior to the prefiring or a reduction agent may be added.
Prefiring is preferably carried out at a 1~ temperature between lOS0 and 1250C in an 02-containing gas atmosphere the partial 2 pressure of which corres-ponds to the equilibrium 2 pressure of the material having the stoichiometric spinel composition at the temperature used.
In this connection, prefiring temperatures between 1100 and 1200C give the best result.
In order to ensure that the powder thus prefired is not oxidized during cooling to room tempera-ture and the blocks obtained from said powder after grinding and compressing are not oxidized during heating to the sintering temperature, said steps should be carried out in a non-oxidizing atmosphere.
The invention also relates to a manganese-zinc-ferrite core obtained while using one of the above mentioned methods, as well as to a magnetic head manu-factured from such a manganese-zinc ferrite core.
The invention will be described in greater detail with reference to the following examples.
EXAMPLE 1.
As a starting material for the preparation of an Mn-Zn ferrite produc~ of the composition .. . .
gL07 3658 PHN 7819 Mn0-574ZnO.354FeO 072Fe2 4 a mixture of Fe3+03 : 63.58% by weight MnC03 : 25.35% by weight ZnO : 11.07% by weight was ground in a ball mill for six hours, prefired in air at a temperature of 850C for four hours and then ground again in a ball mill, again for six hours.
The prefired powder contained a considerable excess of oxygen, since analysis proved that all Fe ions and a part of the Mn ions were present in a trivalent state.
So the powder contained no Fe2 and therefore did not have the stoichiometric spinel composition.
Said powder was compressed to blocks by means of isostatic compression at a pressure of 1000 kg/sq.cm.
Said blocks were sintered in a furnace at a temperature of 1350C for twenty-four hours. Both during heating to the sintering temperature, the sintering, and the cooling to room temperature, a gas mlxture of nitrogen and oxygen was passed through the furnace. The oxygen content was always adapted to the temperature and at 1350C was 10% by volume.
For that purpose the partial oxygen pressure P(02) was adJusted with reference to the relationship log P(02) =
B, where T is temperature in Kelvin, A = -16.039, B = 10~822.
EXAMPLE 2.
In order to prepare an Mn-Zn ferrite product having the same composition as in Example 1, a powder mixture having the same composition as that of Example 1 was prefired ~736~i8 in a flowing nitrogen atmosphere at a temperature of 850C
for four hours, after having been ground in a ball mill for six hours, and was then ground again, this time for eight hours.
s The composition of the prefired powder did not yet satisfy the stoichiometric spinel compositioni it still contained an excess of oxygen, a1beit considerably less than the prefired powder of Example 1.
Said powder was compressed to blocks in the same manner as in Example 1. The blocks were subjected to an extra reduction step before sintering. For that purpose they were heated to a temperature of 1200C in a furnace in which a mixture of nitrogen having 0.1% oxygen was introduced at one end under a small exoess pressure ~0.01 atmosphere) and removed at the other end. They were maintained at the said temperature until the removed gas mixture contained the same amount of oxygen as the intro-duced gas mixture. When said (equilibrium) state was reached, ~he furnace was closed and the temperature was raised to 1350C, at which temperature sintering was carried out ~or twenty-four hours, after which it was cooled. The furnace communicated with a buffer vessel so as to keep the furnace pressure constant during the heating from 1200C to 1350C and during the cooling from 1350C to room temperature.
EXAMPLE 3.
In order to prepare an Mn-Zn ferrite product having the composition Mno.623Zno.~73FeO.104Fe2 04 (this composition was also endeavoured in the followiny examples), a powder mixture havin~ the composition -Fe202 : 64.17% by weight ~C~73~:;5~3 MnC03 : 27.35% by weight ZnO : 8.48% by weight was prefired in air at a temperature of 835C for four hours, after having been ground in a ball mill for four hours, and then ground again for ~our hours This powder was subjected to a reduction step by prefiring it a second time, th;s time in a furnace through which a mixture of nitrogen containing 0.1% oxygen was passed. The prefiring temperature was now 1130C and this temperature was maintained until the removed gas mixture contained the same amount of oxygen as the introduced gas mixture. As soon as said situation had been reached (after approximately five hours) the furnace was filled with pure nitrogen, closed carefully, and cooled to room temperature.
In order to counteract oxidation of the powder during cooling, the furnace communicated with a buffer vessel having a .
variable volume, so that volume \lariations could be com-pensated for and a small excess pressure (0.01 atmosphere) could be maintained during cooling. The resulting powder, after grinding for eight hours, was compressed to blocks.
These blocks were heated to 1200C in a slowly flowing nitrogen atmosphere. The furnace and the buffer vessel were then closed and the temperature was increased to the desired sintering temperature (1350C). Thls temperature was maintained for 24 hours after which the assembly was cooled to room temperature.
EXAMPLE 4.
By a wet-chemical process a powder was prepared from an aqueous solutlon having the following composition:
76.09% by weight of FeS04.7H20, 13.70~ by weight of MnS04.
H20, 10.21% by weight of ZnS04.7H20. This solution was ... .. . ,: : . : .. . .
~365~
spray-dried and the resulting sulphate mixture was f;red in air at 1000C for three hours so as to decompose it.
The resulting powder was prefired at 1130C for five hours in a nitrogen atmosphere containing 0.1% oxygen so as to reduce it. The prefired powder was subjected to the same sintering process as the powder of example 3~ but the s;ntering temperature was 1270C.
Example 5.
A powder having the composition Fe23 o3 54.82% by weight Fe3 04 9.23% by weight ZnO 8.51% by weight MnC03 27.44% by weight (so the required Fe2~ is previously weighed-in in the form of Fe304), after grinding for four hours in a ball mill, was prefired for 2 hours at 1000C in a closed furnace filled with N2 and cooled to room temperature. The furnace remained closed during the whole prefiring cycle (heating, prefiring at 1000C and cooling). The resulting powder was ground for 8 hours and then compressed to blocks by means of isostatic compresslon at 1000 kg/sq.cm. The compressed blocks were heated to 1150C in a closed furnace filled with N2, then sintered at said temperature for 24 hours and then cooled. The furnace remained closed during the whole sintering cycle.
Example 6.
A powder having the composition of the powder of Example 3 was prepared and prefired two times in the same manner as the powder of Example 3. The resulting powder was ground for eight hours and compressed to blocks ~-_ g ... . . . ..
1~73~58 P~N 7819 by means of isostatic compression at lO00 kg/sq.cm.
Said blocks were sintered for twenty-four hours in the manner described in Example 5 but at a temperature of 1230C.
The porosities of the blocks obtained ;n the six Examples were calculated from density measurements and are EXAMPLE l 2 3 4 5 6 . . :
Porosity (% by volume) 5.6 2.6 1.4 0.5 0.5 0.5 From this the conclusion may be drawn that the more the powder to be sintered approaches the stoichiometric spinel composition, the smaller is the porosity of the sintered product.
It was found in particular that this can be reduced from 5.6% to 0.5%.
It is remarkable that the structure of the sintered blocks according to Examples 4, 5 and 6 very much resembles that of Ni Zn ferrite sintered products with the pores in the grains, while normally in Mn-Zn ferrite the pores are present at the grain boundaries.
Moreover it was found that the better the product to be sintered satisfies the sto~chiometrlc sp~nel ~S composition, the lower the sintering temperatures may be chosen to obtain a sufficiently dense final produc~.
-- 1 0 ~
. ~, , ~L~73tj58 PHN 7~19 which have the better magnetic properties and nickel-zinc ferrites which can better withstand detrition. Good detrition properties are of importance in particular when the ferrite heads are used in contact with a high-speed magnetic tape, for example, in video applications. In this connection the porosity of the ferrites plays an important role. For certain applications, for example in video heads, a porosity of the core material is required which may no~exceed a few tenths of a percent. It has so far not been possible to manufacture maganese-zinc-ferro-ferrite cores having such a low porosity via the usual processes. Although a porosity of 0.6% is obtainable, this low porosity was obtained by leading over the ferrite a reducing gas-containing hydrogen during the heating prior to sintering. It should be noted that this process is difficult to control because as a result of exceedingly far redùction other oxidic phases or even metallic phases can easily be formed, so that the composition of the resulting material cannot be readily controlled.
It is the object of the invention to provide a method of the kind mentioned in the preamble with which it is possible to manufacture manganese-zinc-ferro-ferrite cores hav~ng a minimum porosity and a high resistance to detrition.
It has been found that a manganese-zinc-ferrite core which satisfies said requirements can be manufactured if, according to the invention, during one of the steps preceding the sintering, the material to be sintered is given the stoichiometric spinel composition as much as possible.
This is to be understood to mean that in the formula which ~ 1) .~ .;
.
~37 3t;5 ~3 PHN 7819 represents the composition the ratio oF the anions to the cations should approach the ratio 3:4 as much as possible.
In the conventional method of manufacturing manganese-zinc-ferro ferrite cores the starting powders are -prefired in air or nitrogen at temperatures between 800 and 1000C for at most a few hours. The starting powders com-prise an excess of oxygen already prior to the prefiring treatment since the iron component and sometimes also the manganese component is weighed-in in the form of the ~ri-valent ion, that is to say Fe203 and Mn203, respectively~
Also the prefired powders, even those prefired in nitrogen, still contain a considerable excess of oxygen, in other words, they do not have the stoichiometric spinel com-position. They are reduced to said composition only during sintering. Investigations performed by Applicants have proved that in course of things forms an ohstruction for obtaining a low porosity. However, when the material has the stoichiometric spinel composition already at the instant at which it will be sintered, low values of the porosity prove to be realisable indeed.
It is possible within the scope of the invention to reduce a prefired powder which ~oes not have the stoichiomekr~c spinel composition to said compositlon dur~ng heating to the sintering temperature. A problem involved is, however, that it is difficult to reduce the powder integrally in that stagei since it has been compressed to a desired shape at a considerably high pressure ~for example, 1000 kg/sq.cm), the oxygen upon reducing diffuses only slowly from the interior to the exterior.
- - -~'73658 A preferred embodiment of the method according to the invention is therefore characterized in that the material is given the stoichiometric spinel composition as much as possible during the prefiring step. In order to realize this, several reduction methods may be used, for example, the required Fe2 in the form of Fe304 may be added prior to the prefiring or a reduction agent may be added.
Prefiring is preferably carried out at a 1~ temperature between lOS0 and 1250C in an 02-containing gas atmosphere the partial 2 pressure of which corres-ponds to the equilibrium 2 pressure of the material having the stoichiometric spinel composition at the temperature used.
In this connection, prefiring temperatures between 1100 and 1200C give the best result.
In order to ensure that the powder thus prefired is not oxidized during cooling to room tempera-ture and the blocks obtained from said powder after grinding and compressing are not oxidized during heating to the sintering temperature, said steps should be carried out in a non-oxidizing atmosphere.
The invention also relates to a manganese-zinc-ferrite core obtained while using one of the above mentioned methods, as well as to a magnetic head manu-factured from such a manganese-zinc ferrite core.
The invention will be described in greater detail with reference to the following examples.
EXAMPLE 1.
As a starting material for the preparation of an Mn-Zn ferrite produc~ of the composition .. . .
gL07 3658 PHN 7819 Mn0-574ZnO.354FeO 072Fe2 4 a mixture of Fe3+03 : 63.58% by weight MnC03 : 25.35% by weight ZnO : 11.07% by weight was ground in a ball mill for six hours, prefired in air at a temperature of 850C for four hours and then ground again in a ball mill, again for six hours.
The prefired powder contained a considerable excess of oxygen, since analysis proved that all Fe ions and a part of the Mn ions were present in a trivalent state.
So the powder contained no Fe2 and therefore did not have the stoichiometric spinel composition.
Said powder was compressed to blocks by means of isostatic compression at a pressure of 1000 kg/sq.cm.
Said blocks were sintered in a furnace at a temperature of 1350C for twenty-four hours. Both during heating to the sintering temperature, the sintering, and the cooling to room temperature, a gas mlxture of nitrogen and oxygen was passed through the furnace. The oxygen content was always adapted to the temperature and at 1350C was 10% by volume.
For that purpose the partial oxygen pressure P(02) was adJusted with reference to the relationship log P(02) =
B, where T is temperature in Kelvin, A = -16.039, B = 10~822.
EXAMPLE 2.
In order to prepare an Mn-Zn ferrite product having the same composition as in Example 1, a powder mixture having the same composition as that of Example 1 was prefired ~736~i8 in a flowing nitrogen atmosphere at a temperature of 850C
for four hours, after having been ground in a ball mill for six hours, and was then ground again, this time for eight hours.
s The composition of the prefired powder did not yet satisfy the stoichiometric spinel compositioni it still contained an excess of oxygen, a1beit considerably less than the prefired powder of Example 1.
Said powder was compressed to blocks in the same manner as in Example 1. The blocks were subjected to an extra reduction step before sintering. For that purpose they were heated to a temperature of 1200C in a furnace in which a mixture of nitrogen having 0.1% oxygen was introduced at one end under a small exoess pressure ~0.01 atmosphere) and removed at the other end. They were maintained at the said temperature until the removed gas mixture contained the same amount of oxygen as the intro-duced gas mixture. When said (equilibrium) state was reached, ~he furnace was closed and the temperature was raised to 1350C, at which temperature sintering was carried out ~or twenty-four hours, after which it was cooled. The furnace communicated with a buffer vessel so as to keep the furnace pressure constant during the heating from 1200C to 1350C and during the cooling from 1350C to room temperature.
EXAMPLE 3.
In order to prepare an Mn-Zn ferrite product having the composition Mno.623Zno.~73FeO.104Fe2 04 (this composition was also endeavoured in the followiny examples), a powder mixture havin~ the composition -Fe202 : 64.17% by weight ~C~73~:;5~3 MnC03 : 27.35% by weight ZnO : 8.48% by weight was prefired in air at a temperature of 835C for four hours, after having been ground in a ball mill for four hours, and then ground again for ~our hours This powder was subjected to a reduction step by prefiring it a second time, th;s time in a furnace through which a mixture of nitrogen containing 0.1% oxygen was passed. The prefiring temperature was now 1130C and this temperature was maintained until the removed gas mixture contained the same amount of oxygen as the introduced gas mixture. As soon as said situation had been reached (after approximately five hours) the furnace was filled with pure nitrogen, closed carefully, and cooled to room temperature.
In order to counteract oxidation of the powder during cooling, the furnace communicated with a buffer vessel having a .
variable volume, so that volume \lariations could be com-pensated for and a small excess pressure (0.01 atmosphere) could be maintained during cooling. The resulting powder, after grinding for eight hours, was compressed to blocks.
These blocks were heated to 1200C in a slowly flowing nitrogen atmosphere. The furnace and the buffer vessel were then closed and the temperature was increased to the desired sintering temperature (1350C). Thls temperature was maintained for 24 hours after which the assembly was cooled to room temperature.
EXAMPLE 4.
By a wet-chemical process a powder was prepared from an aqueous solutlon having the following composition:
76.09% by weight of FeS04.7H20, 13.70~ by weight of MnS04.
H20, 10.21% by weight of ZnS04.7H20. This solution was ... .. . ,: : . : .. . .
~365~
spray-dried and the resulting sulphate mixture was f;red in air at 1000C for three hours so as to decompose it.
The resulting powder was prefired at 1130C for five hours in a nitrogen atmosphere containing 0.1% oxygen so as to reduce it. The prefired powder was subjected to the same sintering process as the powder of example 3~ but the s;ntering temperature was 1270C.
Example 5.
A powder having the composition Fe23 o3 54.82% by weight Fe3 04 9.23% by weight ZnO 8.51% by weight MnC03 27.44% by weight (so the required Fe2~ is previously weighed-in in the form of Fe304), after grinding for four hours in a ball mill, was prefired for 2 hours at 1000C in a closed furnace filled with N2 and cooled to room temperature. The furnace remained closed during the whole prefiring cycle (heating, prefiring at 1000C and cooling). The resulting powder was ground for 8 hours and then compressed to blocks by means of isostatic compresslon at 1000 kg/sq.cm. The compressed blocks were heated to 1150C in a closed furnace filled with N2, then sintered at said temperature for 24 hours and then cooled. The furnace remained closed during the whole sintering cycle.
Example 6.
A powder having the composition of the powder of Example 3 was prepared and prefired two times in the same manner as the powder of Example 3. The resulting powder was ground for eight hours and compressed to blocks ~-_ g ... . . . ..
1~73~58 P~N 7819 by means of isostatic compression at lO00 kg/sq.cm.
Said blocks were sintered for twenty-four hours in the manner described in Example 5 but at a temperature of 1230C.
The porosities of the blocks obtained ;n the six Examples were calculated from density measurements and are EXAMPLE l 2 3 4 5 6 . . :
Porosity (% by volume) 5.6 2.6 1.4 0.5 0.5 0.5 From this the conclusion may be drawn that the more the powder to be sintered approaches the stoichiometric spinel composition, the smaller is the porosity of the sintered product.
It was found in particular that this can be reduced from 5.6% to 0.5%.
It is remarkable that the structure of the sintered blocks according to Examples 4, 5 and 6 very much resembles that of Ni Zn ferrite sintered products with the pores in the grains, while normally in Mn-Zn ferrite the pores are present at the grain boundaries.
Moreover it was found that the better the product to be sintered satisfies the sto~chiometrlc sp~nel ~S composition, the lower the sintering temperatures may be chosen to obtain a sufficiently dense final produc~.
-- 1 0 ~
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS
1. A method of manufacturing a manganese-zinc-ferrous-ferrite core, in particular for use in magnetic heads, comprising the steps of:
forming a mixture of oxides of iron, manganese, and zinc, or products which provide said oxides;
prefiring said mixture at a temperature between 800 and 1250°C;
grinding the prefired mixture;
compressing the ground prefired mixture to form a body, heating the body in a non-oxidizing atmosphere to the sintering temperature, and sintering the body in a non-oxidizing atmosphere at a temperature between 1050 and 1300°C;
wherein the mixture has a substantially stoichiometric spinel composi-tion prior to the heating step.
forming a mixture of oxides of iron, manganese, and zinc, or products which provide said oxides;
prefiring said mixture at a temperature between 800 and 1250°C;
grinding the prefired mixture;
compressing the ground prefired mixture to form a body, heating the body in a non-oxidizing atmosphere to the sintering temperature, and sintering the body in a non-oxidizing atmosphere at a temperature between 1050 and 1300°C;
wherein the mixture has a substantially stoichiometric spinel composi-tion prior to the heating step.
2. A method as claimed in Claim 1, characterized in that the mixture is given the stoichiometric spinel composition during the prefiring step.
3. A method as claimed in Claim 2, characterized in that prefiring is carried out at a temperature between 800 and 1250°C in an O2-containing gas atmosphere the partial O2 pressure of which corres-ponds to the equilibrium O2 pressure of the material having the stoichiometric spinel composition at the temperature used.
4. A method as claimed in Claim 3, characterized in that prefiring is carried out at a temperature between 1100 and 1200°C.
5. A method as claimed in Claim 2, characterized in that after the prefiring step the mixture is cooled to ambient temperature in a non-oxidizing atmosphere.
6. A method as claimed in Claim 3 or 4, characterized in that the body is sintered at a temperature between 1200 and 1300°C.
7. A method as claimed in Claim 1, characterized in that a mixture is formed which contains the required ferrous iron in the form of Fe3O4.
8. A method as claimed in Claim 7, characterized in that the mixture is pre-fired in a stationary nitrogen atmosphere.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7414706A NL7414706A (en) | 1974-11-12 | 1974-11-12 | PROCESS FOR MANUFACTURE OF A MANGANESE ZINC FERRITE CORE, PARTICULARLY FOR USE IN MAGNETIC HEADS. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1073658A true CA1073658A (en) | 1980-03-18 |
Family
ID=19822445
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA239,375A Expired CA1073658A (en) | 1974-11-12 | 1975-11-06 | Method of manufacturing a manganese-zinc-ferro-ferrite core, in particular for use in magnetic heads |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5170495A (en) |
| BE (1) | BE835447A (en) |
| CA (1) | CA1073658A (en) |
| DE (1) | DE2549085C2 (en) |
| FR (1) | FR2291572A1 (en) |
| GB (1) | GB1523910A (en) |
| NL (1) | NL7414706A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2641319A1 (en) * | 1976-09-14 | 1978-03-16 | Siemens Ag | Manganese zinc ferrite or nickel zinc ferrite core - with low signal-noise ratio in magnetic recording heads |
| NL8002990A (en) * | 1980-05-23 | 1981-12-16 | Philips Nv | METHOD FOR MANUFACTURING AN ANISOTROPIC PERMANENT OXIDE BASED MAGNET |
| US4375657A (en) * | 1980-11-03 | 1983-03-01 | Brock George W | Magnetic head assembly |
| NL8200174A (en) * | 1982-01-19 | 1983-08-16 | Philips Nv | MAGNETIC HEAD OF ZINC-FERRO-FERRITE. |
| CA1242314A (en) * | 1983-12-29 | 1988-09-27 | Ralph W. Scheidecker | Process for controlling ferrous iron content in manganese zinc ferrite |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3557266A (en) * | 1967-02-09 | 1971-01-19 | Matsushita Electric Ind Co Ltd | Method of eliminating the porosity and controlling the grain size of a ferrite body by a two stage hot pressing treatment |
-
1974
- 1974-11-12 NL NL7414706A patent/NL7414706A/en unknown
-
1975
- 1975-10-29 GB GB4462575A patent/GB1523910A/en not_active Expired
- 1975-11-03 DE DE19752549085 patent/DE2549085C2/en not_active Expired
- 1975-11-06 CA CA239,375A patent/CA1073658A/en not_active Expired
- 1975-11-08 JP JP50133650A patent/JPS5170495A/en active Granted
- 1975-11-10 BE BE161758A patent/BE835447A/en not_active IP Right Cessation
- 1975-11-12 FR FR7534440A patent/FR2291572A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5170495A (en) | 1976-06-18 |
| DE2549085C2 (en) | 1985-04-11 |
| FR2291572B1 (en) | 1981-11-27 |
| JPS5524684B2 (en) | 1980-07-01 |
| BE835447A (en) | 1976-05-10 |
| FR2291572A1 (en) | 1976-06-11 |
| GB1523910A (en) | 1978-09-06 |
| DE2549085A1 (en) | 1976-05-13 |
| NL7414706A (en) | 1976-05-14 |
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