JPS6041023B2 - Manufacturing method of lithium-based ferrite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an isolator for microwave circuits,
Magnetic material elements used in circulators, phase shifters, etc.
The present invention also relates to a method of manufacturing lithium-based ferrite used in the external magnetic circuit element.

Traditionally, garnet materials with low loss have been widely used as magnetic material elements for microwave circuits, but lithium-based ferrite is said to be cheaper to manufacture and has better temperature characteristics than garnet materials. It has special features.

Furthermore, it exhibits extremely advantageous properties as a material for a latching type phase shifter, such as a large ratio (squareness ratio) of the residual magnetization value to the saturation magnetization value. However, Li-based ferrite has a larger coercive force (Hc) than garnet, and when used as a magnetic material element for microwave circuits, it requires larger component magnets and drive current devices for applying an external DC magnetic field, and higher performance. This creates a need for change. The coercive force of lithium-based ferrite is 4
・For leveling, it is widely known that a common method is to add bismuth trioxide (Bi203) to ferrite powder. However, when Bi203 is added and fired to obtain a low Hc ferrite, coarse growth of crystal grains occurs and non-uniform deformation occurs.

It is well known that the crystal grain size of ferrite is related to the power resistance characteristics, and that smaller crystal grain sizes are more desirable in terms of power resistance characteristics, and the phenomenon of non-uniform deformation requires dimensional accuracy. However, in the case of products with complex shapes, the product yield was significantly reduced. The present invention is based on the basic composition formula Lio. 5(,chemical-z)TixZLMnaFe2.5-
o. 5(3x+2)404 (However, 0mi x mi0.9
, 0×0.15, 0.01×0.3), Tj02 and Bi203 are mixed at a molar ratio m of 0.14<
Mixing so that m<0.18, and adding 0.2 to 1.3% by weight of oxide powder obtained by heating and melting and crushing to the ferrite powder represented by the above basic composition formula,
By molding and firing, the coarse growth of crystal grain size during firing of the conventional Bj203-added product is suppressed and the drawback of non-uniform deformation is improved.

Hereinafter, the present invention will be explained in detail.
, Zn, and Mn. First, Ti40 ions mainly occupy the octahedral orientation of the spinel structure of ferrite, and as the Ti amount x increases, the saturation magnetization value decreases almost linearly. This is to obtain a known and desired saturation magnetization value.

The saturation magnetization value of ferrite, which is normally used as a magnetic material element for microwave circuits, is considered to be approximately 200 Gauss or more, so the Ti amount x should be in the range of 0.00 to 0.00000. I made it up to 9. Furthermore, the effect of a small amount of Zn20 ions is effective in reducing the magnetic resonance half-maximum △ days, which is a measure of the magnitude of magnetic loss in ferrite for microwave circuits, and in reducing the coercive force Hc. It is known that even a small amount of ions causes a large or medium decrease in the Curie temperature compared to ions that occupy the tetrahedral positions in the spinel structure. Therefore, in the present invention, the maximum value of Zn20 is 0.1 within the effective effect range.
It shall be kept to 5. In addition, regarding the effect of Mn30 ions, if Fe20 ions are generated due to inappropriate oxygen partial pressure during firing, composition deviation from the stoichiometric value of the spinel structure, etc., the electrons between Fe21 ions and Fe30 ions It is known that it is effective in alleviating movement and suppressing increase in dielectric loss. However, when the Mn amount a exceeds 0.3, electrons are exchanged between Mn ions, resulting in an increase in dielectric loss. Therefore, in the present invention, the Mn amount a is the technical maximum value 0.3
That is. In the practice of this invention, commercially available reagent grade carbonates (Li2C03), oxides Ti02, Zn
0,M to 03, Fe203) were used as raw materials, weighed so as to have the proportions according to the basic composition formula, ethyl alcohol was added, and wet mixing and pulverization was performed in a ball mill for 10 hours.

After drying, the mixture was temporarily held at 75°C for 2 hours. After temporary scaling, ethyl alcohol was added again and wet milling was performed in a ball mill for 2 q hours. After pulverization, it was dried to obtain ferrite powder. Next, commercially available reagent-grade Ti02 and Bi203 were weighed so that the molar ratio was m, mixed in a brain sieve machine for 1 hour, then placed in an alumina rubbo, and heated at a rate of 300°C per hour. The mixture was kept warm at 95°C for 1 minute to melt it, and after quenching, it was coarsely ground again in a distiller for 1 hour. Ethyl alcohol was added to the coarsely pulverized powder, which was then finely pulverized in a ball mill for 2 hours and dried to obtain an oxide powder for addition. Ferrite powder and added component Bi203 or Bi20
3-Weigh and collect the oxides for Ti02-based additives so that they have the respective weight ratios, sow them, and mix in a machine for 1 hour. As a subsequent adhesive, add 3% polyvinyl alcohol solution to 1 part by weight. % and spread it evenly over the powder, then mold it to 0. Forming is carried out using 9 on/base pressure, and then further 0.0 on using a hydrostatic press. Pressure molding was performed at a pressure of hbn/m. The shape is approximately 1 for measuring deformed soil.
It is a rectangular body measuring 3 x 13 x 90, and commonly used toroidal and cylindrical molded products were used for magnetic properties and other properties. Firing was carried out in an oxygen atmosphere, kept at a temperature of 450 qo for 1 q hours, and then raised at a rate of 50°C per hour.
After keeping the temperature at 70,000 for 4 hours, the temperature was raised again at a rate of 50 oo per hour, and firing was performed at 95,000 to 1,175 qo for several hours. The amount of deformation was measured by dividing the A dimension by the B dimension of the fired product having the shape shown in FIG. Figure 2 shows the basic composition formula Lio. 5(.10x-z)TixZLMnaFe2.5
−.

．． At 5(3X+Z)-a04, x=0.33, z=
0.05, a=0.15, ferrite powder was prepared by the above method, and five types of molar ratio m of Ti02 and Bi203 were prepared: 0.12, 0.14, 0.10, 0.18, 0.20. Prepare oxide powder for addition of 0.0% to ferrite powder. This is a characteristic diagram when firing for 2 hours at a box weight % additive content of 104,000, where m is taken as the machine axis, and coercive force Hc and average crystal grain size are taken as the machine axis. Hc is m
The average crystal grain size tends to decrease with the value of m, but increases rapidly when the value of m exceeds 0.18. Therefore, the range of m is preferably 0.14<m<0.18. Third
The figure shows the basic composition formula Li 5(, 10X-Z)TiXZLM
naFe2.5-.

．． 5(3X+Z)-. In 04, ×=0.3〆 z
= 0.0 u A = 0.15. Ferrite powder was created by the above method, and an oxide powder for addition with a molar ratio of Ti02 and B;203 of 0.16 was created, and its additive content was This figure shows the relationship between the added content and Hc when firing was performed at 1140 oo with different values. As is clear from Figure 3, the range in which the effect of lowering Hc is significant is 0.2
~1.3% by weight. Next, as an example, Table 1 shows the basic compositional formula and the content of added components.

Table 2 lists their coercive force, saturation magnetization value, average crystal grain size, and yield rate based on the amount of deformation during firing. *
In the table, sample M. Those in parentheses indicate conventional added ingredients, and the same sample No. was conducted under the same firing conditions.

Moreover, the composition of the Bi203-Ti02-based powder, which is an additive, is all m=0.16. Table 1 Table 2 As stated above, this invention applies Bi2 to Li-based ferrite.
The inclusion of 03-Ti02 type additives has the effect of suppressing the coarse growth of crystal grains, lowering the coercive force, reducing deformation during firing, and increasing product durability.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a ferrite rod that has been non-uniformly deformed after firing a rectangular shaped product to be press-molded. Figure 2 is a characteristic diagram showing the relationship between the composition ratio of ferrite containing Bi203-Ti02 additives, coercive force, and average grain size, and Figure 3 is a graph showing the relationship between Bi203-Ti02 additives and coercive force. FIG. Ta 1 figure Z figure Ta J prisoner

Claims (1)

[Claims] 1 Basic compositional formula Li_0. ＿５＿(＿１＿+＿x＿−＿z＿)Ti_x
Zn_zMn_aFe_2. ＿５＿−＿０． ＿５＿(＿
3_x_+_z_)_-_aO_4 (0≦x≦0
．． 9, 0≦z≦0.15, 0.01≦a≦0.3), in which titanium dioxide and bismuth trioxide are combined in a molar ratio m of 0.
．． Mix so that 14≦m≦0.18, heat and melt.
A method for producing lithium-based ferrite, which comprises adding 0.2 to 1.3% by weight of oxide powder obtained by pulverization to ferrite powder represented by the basic composition formula above, and then molding and firing.