Hexagonal z-type ferrite sintered body and manufacturing method thereof

Abstract

The ferrite sintered body of the present invention is a hexagonal Z-type ferrite sintered body having a high permeability and a low anisotropy of permeability, comprising a c-axis-oriented plane in which a degree of orientation fc ⊥ is not less than 0.4, said degree of orientation being given as fc ⊥ =ΣI(HK0)/ΣI(HKL), when I(HKL) is the integrated intensity of a diffraction peak represented by an index (HKL) in an X-ray diffraction pattern of which measurement range is 2θ=20 to 80°, wherein the degree of orientation fc ∥ calculated from fc ∥ =I(0018)/I(110) in an X-ray diffraction is not less than 0.3 in at least two planes which are perpendicular to the aforementioned c-axis-oriented plane and are perpendicular to each other. Where ΣI(HKL) is the sum of integrated intensity of all the diffraction peaks of hexagonal Z-type ferrite.

1 . A hexagonal Z-type ferrite sintered body, comprising: 
 a c-axis-oriented plane in which    a degree of orientation fc ⊥  is not less than 0.4, said degree of orientation being given as fc ⊥ =ΣI(HK0)/ΣI(HKL), where ΣI(HKL) is the sum of integrated intensity of all the diffraction peaks of hexagonal Z-type ferrite and ΣI(HK0) is the sum of integrated intensity of all the diffraction peaks of (HK0) for which L=0 in an X-ray diffraction pattern of which measurement range is 2θ=20 to 80°, when I(HKL) is the integrated intensity of a diffraction peak represented by an index (HKL) wherein    a degree of orientation fc ∥  calculated from fc ∥ =I(0018)/I(110) in an X-ray diffraction is not less than 0.3 in at least two planes which are perpendicular to said c-axis-oriented plane and are perpendicular to each other.    
     
     
         2 . The hexagonal Z-type ferrite sintered body according to  claim 1 , wherein said hexagonal Z-type ferrite sintered body is principally composed of BaO, CoO, and Fe 2 O 3 , and has a Ba-rich composition deviating from the stoichiometric composition Ba 3 CO 2 Fe 24 O 41  of a hexagonal Z-type ferrite.  
     
     
         3 . The hexagonal Z-type ferrite sintered body according to  claim 1 , wherein a sintered body density of said hexagonal Z-type ferrite sintered body is not less than 5.0×10 3  kg/m 3 .  
     
     
         4 . The hexagonal Z-type ferrite sintered body according to  claim 1  wherein a ratio of μ ∥ /μ ⊥ is not more than 0.6 at 100 kHz and/or 100 MHz for permeabilities μ ∥  of at least two directions which are parallel with said c-axis-oriented plane and intersects at right angles to each other, where μ ⊥  is a permeability perpendicular to said c-axis-oriented plane and μ ∥  is a permeability parallel with the said c-axis-oriented plane.  
     
     
         5 . The hexagonal Z-type ferrite sintered body according to  claim 1 , wherein the permeability at 100 kHz in the direction perpendicular to said c-axis-oriented plane is not less than 30.  
     
     
         6 . The hexagonal Z-type ferrite sintered body according to  claim 1 , wherein the permeability at 100 kHz in a direction parallel with said c-axis-oriented plane is not less than 8.  
     
     
         7 . The hexagonal Z-type ferrite sintered body according to  claim 1 , wherein said hexagonal Z-type ferrite sintered body has a machined surface.  
     
     
         8 . A hexagonal Z-type ferrite sintered body, comprising: 
 a c-axis-oriented plane of which an average orientation difference θ AV  represented as θ AV =Σθn(θ)/Σn(θ) is not less than 65° in an orientation analysis by EBSP (Electron Back Scattering Pattern), wherein    a value SD/n AV , which is given by dividing a standard deviation SD given by SD={Σ(I(φ)−n AV ) 2 /m} 1/2  by an average value of the number of measurement points given by n AV =ΣI(φ)/m, is not more than 0.6 (where, θ: orientation angle difference between the direction perpendicular to the orientation analysis plane of hexagonal Z-type ferrite sintered body and the c-axis direction of the hexagonal Z-type ferrite at the measurement position of EBSP, n(θ): the number of measurement points to indicate said θ, Σθn(θ): the summation of θn(θ) in the interval of 0 to 90°, Σn(θ): summation of n(θ) in the interval of 0 to 90°, φ: the positive acute angle which is the orientation difference between the projection direction of c-axis direction to said orientation analysis plane and one straight line in said orientation analysis plane, I(φ): the number of measurement points to indicate orientation difference φ, and m: the number of dividing points in the interval of 0 to 90°.)    
     
     
         9 . The hexagonal Z-type ferrite sintered body according to  claim 8 , wherein said hexagonal Z-type ferrite sintered body is principally composed of BaO, CoO, and Fe 2 O 3 , and has a Ba-rich composition deviating from the stoichiometric composition Ba 3 CO 2 Fe 24 O 41  of a hexagonal Z-type ferrite.  
     
     
         10 . The hexagonal Z-type ferrite sintered body according to  claim 8 , wherein a sintered body density of said hexagonal Z-type ferrite sintered body is not less than 5.0×10 3  kg/m 3 .  
     
     
         11 . The hexagonal Z-type ferrite sintered body according to  claim 8 , wherein a ratio of μ ∥ /μ ⊥  is not more than 0.6 at 100 kHz and/or 100 MHz for permeabilities μ ∥  of at least two directions which are parallel with said c-axis-oriented plane and intersects at right angles to each other, where μ ⊥  is a permeability perpendicular to said c-axis-oriented plane and μ ∥  is a permeability parallel with the said c-axis-oriented plane.  
     
     
         12 . The hexagonal Z-type ferrite sintered body according to  claim 8 , wherein the permeability at 100 kHz in the direction perpendicular to said c-axis-oriented plane is not less than 30.  
     
     
         13 . The hexagonal Z-type ferrite sintered body according to  claim 8 , wherein the permeability at 100 kHz in a direction parallel with said c-axis-oriented plane is not less than 8.  
     
     
         14 . The hexagonal Z-type ferrite sintered body according to  claim 8 , wherein said hexagonal Z-type ferrite sintered body has a machined surface.  
     
     
         15 . A method of manufacturing a hexagonal Z-type ferrite sintered body, comprising the steps of: 
 forming a hexagonal Z-type ferrite powder which has a specific surface area of 800 to 4000 m 2 /kg in a uniaxial magnetic field to obtain a green body; and    sintering said green body.    
     
     
         16 . The method of manufacturing a hexagonal Z-type ferrite sintered body according to  claim 15 , wherein 
 forming is performed by mixing said hexagonal Z-type ferrite powder with water to make a slurry so that the concentration of the hexagonal Z-type ferrite powder in said slurry is not more than 70% by weight.    
     
     
         17 . The method of manufacturing a hexagonal Z-type ferrite sintered body according to  claim 16 , wherein 
 forming is performed after stirring said hexagonal Z-type ferrite powder in a die cavity while applying a magnetic field.    
     
     
         18 . The method of manufacturing a hexagonal Z-type ferrite sintered body according to  claim 15 , wherein 
 said hexagonal Z-type ferrite powder is obtained by pulverizing a hexagonal Z-type ferrite sintered body.