MANGANESE ZINC FERRITE, PREPARATION METHOD THEREFOR AND USE THEREOF

Abstract

Disclosed are a manganese zinc ferrite, a preparation method therefor and the use thereof. The manganese zinc ferrite comprises main components and auxiliary components, wherein the main components comprise iron oxide, zinc oxide and manganese monoxide; and according to the total amount of 100 mol % of the main components, the content of ferric oxide is 52.75-53.15 mol %, the content of zinc oxide is 9.1-10.7 mol %, and the balance being manganese monoxide.

Claims

1. A manganese zinc ferrite comprising a main component and an auxiliary component, the main component comprises iron oxide, zinc oxide and manganese monoxide; based on a total amount of the main component being 100 mol %, a content of iron oxide is 52.75-53.15 mol %, a content of zinc oxide is 9.1-10.7 mol % and a remainder is manganese monoxide.

2. The manganese zinc ferrite according to claim 1, wherein the auxiliary component comprises cobalt oxide.

3. The manganese zinc ferrite according to claim 2, wherein the auxiliary component further comprises calcium carbonate and zirconium oxide.

4. The manganese zinc ferrite according to claim 1, wherein under test conditions at a test frequency of 100 kHz and a magnetic flux density of 200 mT, the manganese zinc ferrite has a loss of less than 230 kW/m.sup.3 in a 25 C. environment; optionally, under test conditions at a test frequency of 100 kHz and a magnetic flux density of 200 mT, the manganese zinc ferrite has a loss of less than 230 kW/m.sup.3 in a 60 C. environment; optionally, under test conditions at a test frequency of 100 kHz and a magnetic flux density of 200 mT, the manganese zinc ferrite has a loss of less than 250 kW/m.sup.3 in a 80 C. environment; optionally, under test conditions at a test frequency of 100 kHz and a magnetic flux density of 200 mT, the manganese zinc ferrite has a loss of less than 290 kW/m.sup.3 at 100 C.; optionally, under test conditions at a test frequency of 50 Hz and a magnetic field intensity of 1194 A/m, the ferrite has a saturation magnetic flux density of more than 430 mT in a 100 C. environment.

5. A preparation method for the manganese zinc ferrite according to claim 1, comprising: mixing iron oxide, zinc oxide and manganese monoxide at a ratio and then performing primary wet grinding, pre-sintering the obtained wet material to obtain a pre-sintered material, adding an auxiliary component into the pre-sintered material and then performing secondary wet grinding, performing compression molding and sintering to obtain the manganese zinc ferrite.

6. The preparation method according to claim 5, wherein the preparation method specifically comprises: (I) mixing iron oxide, zinc oxide and manganese monoxide at a ratio to obtain a main component, mixing the main component with water and then performing primary wet grinding, adding a binder into the obtained wet main component and then performing granulation and pre-sintering sequentially to obtain a pre-sintered material; and (II) mixing the pre-sintered material with an auxiliary component to obtain a sintered material, mixing the sintered material with water and performing secondary wet grinding, adding a binder into the obtained wet sintered material and then performing granulation, molding and sintering sequentially to obtain the manganese zinc ferrite.

7. The preparation method according to claim 6, wherein in step (I), based on a total amount of the main component being 100 mol %, a content of iron oxide is 52.75-53.15 mol %, a content of zinc oxide is 9.1-10.7 mol % and a remainder is manganese monoxide; optionally, the primary wet grinding is ball milling; optionally, during the primary wet grinding, the main component, balls and water have a mass ratio of 1:(5-8):(0.4-0.6); optionally, a mass of the binder added into the wet main component is 8-10 wt % of a total mass of the wet main component, optionally 7.5-10 wt %.

8. The preparation method according to claim 6, wherein in step (I), the granulation is spray granulation; optionally, during the spray granulation, a material inlet temperature is 320-350 C.; optionally, during the spray granulation, a material outlet temperature is 85-100 C.; optionally, the pre-sintering is performed in a rotary kiln; optionally, the pre-sintering is performed at 850-950 C.; optionally, the pre-sintering is performed for 3-6 h.

9. The preparation method according to claim 6, wherein in step (II), the auxiliary component comprises cobalt oxide; optionally, the auxiliary component is calcium carbonate, zirconium oxide and cobalt oxide; optionally, a content of calcium carbonate added into the pre-sintered material is 0.06-0.08 wt % of a total mass of the pre-sintered material; optionally, a content of zirconium oxide added into the pre-sintered material is 0.02-0.04 wt % of a total mass of the pre-sintered material; optionally, a content of cobalt oxide added into the pre-sintered material is 0.35-0.39 wt % of a total mass of the pre-sintered material; optionally, the secondary wet grinding is ball milling; optionally, during the secondary wet grinding, the sintered material, balls and water have a mass ratio of 1:(5-8):(0.4-0.6); optionally, a mass of the binder added into the wet sintered material is 8-10 wt % of a total mass of the wet sintered material, optionally 7.5-10 wt %.

10. The preparation method according to claim 6, wherein in step (II), the granulation is spray granulation; optionally, during the spray granulation, a material inlet temperature is 320-350 C.; optionally, during the spray granulation, a material outlet temperature is 85-100 C.; optionally, the molding comprises performing compression at 5-10 MPa to prepare a standard ring; optionally, the sintering is performed in a bell jar furnace; optionally, the sintering comprises a sintering section and a cooling section which are performed sequentially; optionally, the sintering section is performed at 1290-1320 C.; optionally, the sintering section has a holding time of 3-6 h; optionally, the sintering section has an oxygen content of 3-6%; optionally, the cooling section is divided into an earlier cooling section and a later cooling section which are performed sequentially, and the later cooling section comprises a first cooling section and a second cooling section which are performed sequentially; optionally, the earlier cooling section comprises cooling from an end temperature of the sintering section to an initial temperature of the first cooling section; optionally, the first cooling section is cooling from 450 C. to 280 C.; optionally, the second cooling section is cooling from 280 C. to 50 C.; optionally, the first cooling section has an oxygen content of 0.02-0.15%; optionally, the second cooling section has an oxygen content of 0%; optionally, the later cooling section has a cooling rate of 0.05-0.3 C./min.

11. Use of the manganese zinc ferrite according to claim 1, wherein the manganese zinc ferrite is used for a power adapter.

Description

DETAILED DESCRIPTION

[0068] The technical solutions of the present application are further described below through specific embodiments.

Example 1

[0069] This example provides a preparation method for a manganese zinc ferrite, and the preparation method specifically includes the following steps: [0070] i. the 52.75 mol % of Fe.sub.2O.sub.3, 38.15 mol % of MnO and 9.1 mol % of ZnO were mixed to obtain a main component, and the main component was mixed with water and subjected to primary wet grinding for 0.5 h, and the main component, balls and water had a mass ratio of 1:5:0.4; [0071] ii. the obtained wet main component was added with a binder (a mass fraction of the binder was 7.5 wt %) and then subjected to spray granulation and pre-sintering sequentially to obtain a pre-sintered material, and a mass of the binder added was 8 wt % of a total mass of the wet main component; during the spray granulation, a material inlet temperature was 320 C., and a material outlet temperature was 85 C.; the pre-sintering was performed at 850 C. for 3 h in a rotary kiln; [0072] iii. the pre-sintered material was added with calcium carbonate, zirconium oxide and cobalt oxide, wherein an addition amount of calcium carbonate was 0.06 wt % of a total mass of the pre-sintered material, an addition amount of zirconium oxide was 0.02 wt % of a total mass of the pre-sintered material, and an addition amount of cobalt oxide was 0.35 wt % of a total mass of the pre-sintered material, the materials were mixed uniformly to obtain a sintered material, the sintered material was mixed with water and subjected to secondary wet grinding for 1.5 h to obtain the wet sintered material, and the sintered material, balls and water had a mass ratio of 1:5:0.4; and [0073] iv. the sintered wet material was added with a binder (a mass fraction of the binder was 7.5 wt %) and then subjected to spray granulation, molding and sintering sequentially to obtain the manganese zinc ferrite, and a mass of the binder added in the wet sintered material was 8 wt % of a total mass of the wet sintered material; during the spray granulation, a material inlet temperature was 320 C., and a material outlet temperature was 85 C.; compression was performed at 5 MPa to prepare a standard ring; the sintering was performed in a bell jar furnace, the sintering included a sintering section and a cooling section which were performed sequentially, the sintering section was performed at 1290 C., the sintering section had a holding time of 3 h, the sintering section had an oxygen content of 3%, the cooling section was divided into an earlier cooling section and a later cooling section which were performed sequentially, the earlier cooling section was cooling from 1290 C. to 450 C., the later cooling section included a first cooling section and a second cooling section which were performed sequentially, the first cooling section was cooling from 450 C. to 280 C., the first cooling section had an oxygen content of 0.08%, the second cooling section was cooling from 280 C. to 50 C., the second cooling section had an oxygen content of 0%, and the first cooling section and the second cooling section both had a cooling rate of 0.05 C./min.

Example 2

[0074] This example provides a preparation method for a manganese zinc ferrite, and the preparation method specifically includes the following steps: [0075] i. the 52.8 mol % of Fe.sub.2O.sub.3, 37.9 mol % of MnO and 9.3 mol % of ZnO were mixed to obtain a main component, and the main component was mixed with water and subjected to primary wet grinding for 0.5 h, and the main component, balls and water had a mass ratio of 1:5:0.5; [0076] ii. the obtained wet main component was added with a binder (a mass fraction of the binder was 8 wt %) and then subjected to spray granulation and pre-sintering sequentially to obtain a pre-sintered material, and a mass of the binder added was 8.4 wt % of a total mass of the wet main component; during the spray granulation, a material inlet temperature was 326 C., and a material outlet temperature was 88 C.; the pre-sintering was performed at 870 C. for 3.6 h in a rotary kiln; [0077] iii. the pre-sintered material was added with calcium carbonate, zirconium oxide and cobalt oxide, wherein an addition amount of calcium carbonate was 0.065 wt % of a total mass of the pre-sintered material, an addition amount of zirconium oxide was 0.024 wt % of a total mass of the pre-sintered material, and an addition amount of cobalt oxide was 0.358 wt % of a total mass of the pre-sintered material, the materials were mixed uniformly to obtain a sintered material, the sintered material was mixed with water and subjected to secondary wet grinding for 1.5 h to obtain the wet sintered material, and the sintered material, balls and water had a mass ratio of 1:5:0.5; and [0078] iv. the sintered wet material was added with a binder (a mass fraction of the binder was 8 wt %) and then subjected to spray granulation, molding and sintering sequentially to obtain the manganese zinc ferrite, and a mass of the binder added in the wet sintered material was 8.4 wt % of a total mass of the wet sintered material; during the spray granulation, a material inlet temperature was 326 C., and a material outlet temperature was 88 C.; compression was performed at 6 MPa to prepare a standard ring; the sintering was performed in a bell jar furnace, the sintering included a sintering section and a cooling section which were performed sequentially, the sintering section was performed at 1296 C., the sintering section had a holding time of 3.6 h, the sintering section had an oxygen content of 3.6%, the cooling section was divided into an earlier cooling section and a later cooling section which were performed sequentially, the earlier cooling section was cooling from 1296 C. to 450 C., the later cooling section included a first cooling section and a second cooling section which were performed sequentially, the first cooling section was cooling from 450 C. to 280 C., the first cooling section had an oxygen content of 0.1%, the second cooling section was cooling from 280 C. to 50 C., the second cooling section had an oxygen content of 0%, and the first cooling section and the second cooling section both had a cooling rate of 0.1 C./min.

Example 3

[0079] This example provides a preparation method for a manganese zinc ferrite, and the preparation method specifically includes the following steps: [0080] i. the 52.9 mol % of Fe.sub.2O.sub.3, 37.6 mol % of MnO and 9.5 mol % of ZnO were mixed to obtain a main component, and the main component was mixed with water and subjected to primary wet grinding for 0.5 h, and the main component, balls and water had a mass ratio of 1:6:0.5; [0081] ii. the obtained wet main component was added with a binder (a mass fraction of the binder was 8.5 wt %) and then subjected to spray granulation and pre-sintering sequentially to obtain a pre-sintered material, and a mass of the binder added was 8.8 wt % of a total mass of the wet main component; during the spray granulation, a material inlet temperature was 332 C., and a material outlet temperature was 91 C.; the pre-sintering was performed at 890 C. for 4.2 h in a rotary kiln; [0082] iii. the pre-sintered material was added with calcium carbonate, zirconium oxide and cobalt oxide, wherein an addition amount of calcium carbonate was 0.07 wt % of a total mass of the pre-sintered material, an addition amount of zirconium oxide was 0.028 wt % of a total mass of the pre-sintered material, and an addition amount of cobalt oxide was 0.366 wt % of a total mass of the pre-sintered material, the materials were mixed uniformly to obtain a sintered material, the sintered material was mixed with water and subjected to secondary wet grinding for 1.5 h to obtain the wet sintered material, and the sintered material, balls and water had a mass ratio of 1:6:0.5; and [0083] iv. the sintered wet material was added with a binder (a mass fraction of the binder was 8.5 wt %) and then subjected to spray granulation, molding and sintering sequentially to obtain the manganese zinc ferrite, and a mass of the binder added in the wet sintered material was 8.8 wt % of a total mass of the wet sintered material; during the spray granulation, a material inlet temperature was 332 C., and a material outlet temperature was 91 C.; compression was performed at 7 MPa to prepare a standard ring; the sintering was performed in a bell jar furnace, the sintering included a sintering section and a cooling section which were performed sequentially, the sintering section was performed at 1300 C., the sintering section had a holding time of 4.2 h, the sintering section had an oxygen content of 4.2%, the cooling section was divided into an earlier cooling section and a later cooling section which were performed sequentially, the earlier cooling section was cooling from 1300 C. to 450 C., the later cooling section included a first cooling section and a second cooling section which were performed sequentially, the first cooling section was cooling from 450 C. to 280 C., the first cooling section had an oxygen content of 0.15%, the second cooling section was cooling from 280 C. to 50 C., the second cooling section had an oxygen content of 0%, and the first cooling section and the second cooling section both had a cooling rate of 0.15 C./min.

Example 4

[0084] This example provides a preparation method for a manganese zinc ferrite, and the preparation method specifically includes the following steps: [0085] i. the 53 mol % of Fe.sub.2O.sub.3, 37 mol % of MnO and 10 mol % of ZnO were mixed to obtain a main component, and the main component was mixed with water and subjected to primary wet grinding for 0.5 h, and the main component, balls and water had a mass ratio of 1:7:0.5; [0086] ii. the obtained wet main component was added with a binder (a mass fraction of the binder was 9 wt %) and then subjected to spray granulation and pre-sintering sequentially to obtain a pre-sintered material, and a mass of the binder added was 9.2 wt % of a total mass of the wet main component; during the spray granulation, a material inlet temperature was 338 C., and a material outlet temperature was 94 C.; the pre-sintering was performed at 910 C. for 4.8 h in a rotary kiln; [0087] iii. the pre-sintered material was added with calcium carbonate, zirconium oxide and cobalt oxide, wherein an addition amount of calcium carbonate was 0.073 wt % of a total mass of the pre-sintered material, an addition amount of zirconium oxide was 0.032 wt % of a total mass of the pre-sintered material, and an addition amount of cobalt oxide was 0.374 wt % of a total mass of the pre-sintered material, the materials were mixed uniformly to obtain a sintered material, the sintered material was mixed with water and subjected to secondary wet grinding for 1.5 h to obtain the wet sintered material, and the sintered material, balls and water had a mass ratio of 1:7:0.5; and [0088] iv. the sintered wet material was added with a binder (a mass fraction of the binder was 9 wt %) and then subjected to spray granulation, molding and sintering sequentially to obtain the manganese zinc ferrite, and a mass of the binder added in the wet sintered material was 9.2 wt % of a total mass of the wet sintered material; during the spray granulation, a material inlet temperature was 338 C., and a material outlet temperature was 94 C.; compression was performed at 8 MPa to prepare a standard ring; the sintering was performed in a bell jar furnace, the sintering included a sintering section and a cooling section which were performed sequentially, the sintering section was performed at 1308 C., the sintering section had a holding time of 4.8 h, the sintering section had an oxygen content of 5%, the cooling section was divided into an earlier cooling section and a later cooling section which were performed sequentially, the earlier cooling section was cooling from 1308 C. to 450 C., the later cooling section included a first cooling section and a second cooling section which were performed sequentially, the first cooling section was cooling from 450 C. to 280 C., the first cooling section had an oxygen content of 0.15%, the second cooling section was cooling from 280 C. to 50 C., the second cooling section had an oxygen content of 0%, and the first cooling section and the second cooling section both had a cooling rate of 0.2 C./min.

Example 5

[0089] This example provides a preparation method for a manganese zinc ferrite, and the preparation method specifically includes the following steps: [0090] i. the 53.1 mol % of Fe.sub.2O.sub.3, 36.6 mol % of MnO and 10.3 mol % of ZnO were mixed to obtain a main component, and the main component was mixed with water and subjected to primary wet grinding for 0.5 h, and the main component, balls and water had a mass ratio of 1:7:0.6; [0091] ii. the obtained wet main component was added with a binder (a mass fraction of the binder was 9.5 wt %) and then subjected to spray granulation and pre-sintering sequentially to obtain a pre-sintered material, and a mass of the binder added was 9.6 wt % of a total mass of the wet main component; during the spray granulation, a material inlet temperature was 344 C., and a material outlet temperature was 97 C.; the pre-sintering was performed at 930 C. for 5.4 h in a rotary kiln; [0092] iii. the pre-sintered material was added with calcium carbonate, zirconium oxide and cobalt oxide, wherein an addition amount of calcium carbonate was 0.076 wt % of a total mass of the pre-sintered material, an addition amount of zirconium oxide was 0.036 wt % of a total mass of the pre-sintered material, and an addition amount of cobalt oxide was 0.382 wt % of a total mass of the pre-sintered material, the materials were mixed uniformly to obtain a sintered material, the sintered material was mixed with water and subjected to secondary wet grinding for 1.5 h to obtain the wet sintered material, and the sintered material, balls and water had a mass ratio of 1:7:0.6; and [0093] iv. the sintered wet material was added with a binder (a mass fraction of the binder was 9.5 wt %) and then subjected to spray granulation, molding and sintering sequentially to obtain the manganese zinc ferrite, and a mass of the binder added in the wet sintered material was 9.6 wt % of a total mass of the wet sintered material; during the spray granulation, a material inlet temperature was 344 C., and a material outlet temperature was 97 C.; compression was performed at 9 MPa to prepare a standard ring; the sintering was performed in a bell jar furnace, the sintering included a sintering section and a cooling section which were performed sequentially, the sintering section was performed at 1314 C., the sintering section had a holding time of 5.4 h, the sintering section had an oxygen content of 5.5%, the cooling section was divided into an earlier cooling section and a later cooling section which were performed sequentially, the earlier cooling section was cooling from 1314 C. to 450 C., the later cooling section included a first cooling section and a second cooling section which were performed sequentially, the first cooling section was cooling from 450 C. to 280 C., the first cooling section had an oxygen content of 0.12%, the second cooling section was cooling from 280 C. to 50 C., the second cooling section had an oxygen content of 0%, and the first cooling section and the second cooling section both had a cooling rate of 0.25 C./min.

Example 6

[0094] This example provides a preparation method for a manganese zinc ferrite, and the preparation method specifically includes the following steps: [0095] i. the 53.15 mol % of Fe.sub.2O.sub.3, 36.15 mol % of MnO and 10.7 mol % of ZnO were mixed to obtain a main component, and the main component was mixed with water and subjected to primary wet grinding for 0.5 h, and the main component, balls and water had a mass ratio of 1:8:0.6; [0096] ii. the obtained wet main component was added with a binder (a mass fraction of the binder was 10 wt %) and then subjected to spray granulation and pre-sintering sequentially to obtain a pre-sintered material, and a mass of the binder added was 10 wt % of a total mass of the wet main component; during the spray granulation, a material inlet temperature was 350 C., and a material outlet temperature was 100 C.; the pre-sintering was performed at 950 C. for 6 h in a rotary kiln; [0097] iii. the pre-sintered material was added with calcium carbonate, zirconium oxide and cobalt oxide, wherein an addition amount of calcium carbonate was 0.08 wt % of a total mass of the pre-sintered material, an addition amount of zirconium oxide was 0.04 wt % of a total mass of the pre-sintered material, and an addition amount of cobalt oxide was 0.39 wt % of a total mass of the pre-sintered material, the materials were mixed uniformly to obtain a sintered material, the sintered material was mixed with water and subjected to secondary wet grinding for 1.5 h to obtain the wet sintered material, and the sintered material, balls and water had a mass ratio of 1:8:0.6; and [0098] iv. the sintered wet material was added with a binder (a mass fraction of the binder was 10 wt %) and then subjected to spray granulation, molding and sintering sequentially to obtain the manganese zinc ferrite, and a mass of the binder added in the wet sintered material was 10 wt % of a total mass of the wet sintered material; during the spray granulation, a material inlet temperature was 350 C., and a material outlet temperature was 100 C.; compression was performed at 10 MPa to prepare a standard ring; the sintering was performed in a bell jar furnace, the sintering included a sintering section and a cooling section which were performed sequentially, the sintering section was performed at 1320 C., the sintering section had a holding time of 6 h, the sintering section had an oxygen content of 6%, the cooling section was divided into an earlier cooling section and a later cooling section which were performed sequentially, the earlier cooling section was cooling from 1320 C. to 450 C., the later cooling section included a first cooling section and a second cooling section which were performed sequentially, the first cooling section was cooling from 450 C. to 280 C., the first cooling section had an oxygen content of 0.11%, the second cooling section was cooling from 280 C. to 50 C., the second cooling section had an oxygen content of 0%, and the first cooling section and the second cooling section both had a cooling rate of 0.3 C./min.

Comparative Example 1

[0099] This comparative example provides a preparation method for a manganese zinc ferrite, which differs from Example 1 in that the main component in step (1) adopted the following formula: 53.3 mol % of Fe.sub.2O.sub.3, 37.6 mol % of MnO and 9.1 mol % of ZnO. Other operation steps and process parameters are identical to those of Example 1.

Comparative Example 2

[0100] This comparative example provides a preparation method for a manganese zinc ferrite, which differs from Example 1 in that the main component in step (1) adopted the following formula: 52.8 mol % of Fe.sub.2O.sub.3, 36.2 mol % of MnO and 11 mol % of ZnO. Other operation steps and process parameters are identical to those of Example 1.

Comparative Example 3

[0101] This comparative example provides a preparation method for a manganese zinc ferrite, which differs from Example 1 in that an addition amount of cobalt oxide in step (3) was 0.5 wt % of a total mass of the pre-sintering material. Other operation steps and process parameters are identical to those of Example 1.

Comparative Example 4

[0102] This comparative example provides a preparation method for a manganese zinc ferrite, which differs from Example 1 in that step (4) adopted the following sintering method: [0103] the sintering was performed in a bell jar furnace, the sintering included a sintering section and a cooling section which were performed sequentially, the sintering section was performed at 1290 C., the sintering section had a holding time of 3 h, the sintering section had an oxygen content of 3%, the cooling section was divided into an earlier cooling section and a later cooling section which were performed sequentially, the earlier cooling section was cooling from 1290 C. to 450 C., the later cooling section included a first cooling section and a second cooling section which were performed sequentially, the first cooling section was cooling from 450 C. to 280 C., the first cooling section had an oxygen content of 0.001%, the second cooling section was cooling from 280 C. to 50 C., the second cooling section had an oxygen content of 0%, and the first cooling section and the second cooling section both had a cooling rate of 0.05 C./min.

[0104] Except for the above sintering process, the preparation method provided by this comparative example is identical to Example 1.

[0105] The manganese zinc ferrites prepared in Examples 1-6 and Comparative Examples 1-4 are tested for the loss over a wide temperature range and Bs at 100 C. Test conditions of the loss over a wide temperature range are a testing power of 100 kHz and a magnetic flux density of 200 mT. The power loss of the manganese zinc ferrite is tested at 25 C., 60 C., 80 C. and 100 C. separately, and the higher the power loss value, the worse the loss over a wide temperature range for the manganese zinc ferrite. Test conditions of Bs are a testing power of 50 Hz and a magnetic field intensity of 1194 m/A. The test results are shown in Table 1.

TABLE-US-00001 TABLE 1 Power loss [kW/m.sup.3] Bs [mT] 25 C. 60 C. 80 C. 100 C. 100 C. Example 1 223 225 241 285 435 Example 2 220 226 245 283 432 Example 3 222 224 241 286 436 Example 4 225 226 241 283 433 Example 5 222 226 242 284 435 Example 6 226 225 246 288 437 Comparative 280 300 330 350 440 Example 1 Comparative 300 310 330 365 420 Example 2 Comparative 280 310 345 355 428 Example 3 Comparative 260 285 315 345 430 Example 4

[0106] It can be seen from the test data in Table 1 that the Fe.sub.2O.sub.3 content in Comparative Example 1 is too high compared with Example 1, resulting in high power loss and poor loss over a wide temperature range of the manganese zinc ferrite. The ZnO content in Comparative Example 2 is too high compared with Example 1, resulting in high power loss of the manganese zinc ferrite as well as low Bs of the manganese zinc ferrite. The Co.sub.2O.sub.3 content in Comparative Example 3 is too high compared with Example 1, resulting in high power loss of the manganese zinc ferrite as well as low Bs of the manganese zinc ferrite. The oxygen content in Comparative Example 4 is relatively low compared with Example 1, resulting in high power loss and poor loss over a wide temperature range of the manganese zinc ferrite.

[0107] The applicant declares that although the specific embodiments of the present application are described above, the protection scope of the present application is not limited thereto, and the protection scope of the present application is defined by the claims.