DE2647893A1 - LITHIUM FERRITE - Google Patents

Description

Patent attorneys

Dipl.-Ing. Dipl.-Chem. Dipl.-Ing. i £ U H / O J O

E. Prince - Dr. G. Hauser - G. Leiser

Ernsbergerstrasse 19

8 Munich 60

• 3.

THOMSON - CSF October 20, 1976

173 j Bd.Haus smann
75003 Paris / France

Our reference: T 2092

Lithium ferrite

The invention relates to ferromagnetic materials Lithium base, more precisely lithium, titanium and optionally zinc-containing ferrites with a spinel structure and with very low dielectric or magnetic losses at a very high frequency.

At operating frequencies above 6 GHz, the known materials have various disadvantages:

- ferrites with a garnet structure due to their presence rare earths and sintering temperatures above 1400 C have a high cost price;

- The nickel ferrites with a spinous structure are exceptional high magnetic and electrical losses;

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- Ferrites with a spinel structure based on manganese and magnesium have a fundamentally low Curie point ;

- the ferrites with spinel structure based on lithium and aluminum too high dielectric losses.

The invention enables these disadvantages to be eliminated.

The ferrites according to the invention correspond to the following general formula:

^Li 0.5 (1 + Y) ^Zn X ^Fe 0.5 (5 - 3Y - 4X) ^Ti X + YO ₄ O-Bi ₂ O ₃

β Mn O ₂ (I),

where: 0 ^ X ^ 0.4

0.1 <. X · (- Y <0.9
0.001 <oc <0.01
0.05 </ S <0.25

The variable Y can assume negative values in the range from 0 to -0.4.

In formula (I) one wanted to express that:

- once stoichiometric components (or approximately stoichiometric) are present in the proportions determined by the sizes X and Y;

- on the other hand, non-stoichiometric components are present which were added as flux and are in a different from the crystalline phase of the spinel Phase present; it is bismuth and Manganese oxides.

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The formula (I) indicates the final composition of the ferrite and the quantities of the starting materials (salts and oxides) are of course calculated taking into account later additions or removals of elements during manufacture; For example, iron can be introduced into a ball mill during grinding and lithium during the
Burning to be evaporated.

These substances can be obtained by a method known for the production of polycrystalline ferrites v / earth; such a process includes, for example, the following stages:

a) Mixing very pure oxides or salts (degree of purity over 99.9 %) in the amount corresponding to the selected formula with distilled water or alcohol, taking into account losses or introductions of elements, as they result from the following steps j

b) first grinding this mixture for 24 hours in steel bottles containing steel balls;

c) drying in a drying oven, followed by baking in an oven at about 800 ^° C .;

d) grinding the product obtained a second time in aqueous

or alcoholic medium under the same conditions as during the first grinding process, but 12 to Hours longer, namely 36 to 48 hours;

e) drying and sieving the powder thus obtained;

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f) forming, either by pressing in a steel mold, which requires the addition of a binder (which then by heating to 600 ⁰ C expelled v / can ground), or by "isostatic pressing in a rubber mold ^11;

g) sintering under oxygen at a temperature between 950 and 1100 ^° C. for 6 to 16 hours.

The invention is explained in more detail with reference to the following examples, in which the following fourth has been chosen for the sizes & and fi : cc = 0.003 _s ß = 0.14, and a sintering temperature (stage g) of 1025 ± 50 ^° C. »In addition the iron deficiency in step (a) was set at 10% of the molar value.

The results obtained are divided into three groups: First example group: X = O

There is no zinc present and the spinel is a so-called "lithium-titanium spinel ^fi . Table 1 gives the results obtained for the following quantities:

tg6 10

magnetic saturation moment in Gauss;

Curie temperature in degrees Celsius j

gyromagnetic resonance line width in Oersted;

effective gyromagnetic pactor;

the real component of the dielectric constant

Tangent of the dielectric loss angle (value

multiplied by 10,000);

ΔΗ,: width of the resonance line of the spin wave ( ^{linked to the v} magnetic losses).

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4nM _s ^G Curie - 3 - 1 Seff V 264 7893 (Gauss) ( ⁰ C) Λ. 2950 554 Tabel 2.08 16.6 Y 2735 545 ΔΗ 2.08 16.6 tg6iC ) ⁴ ΔΗ _χ 2500 531 (Oe) 2.08 16.8 (Oe) 0.115 2280 515 4oo 2.08 16.9 2.4 1.8 0.150 2100 495 560 2.07 17.1 4.2 2.4 0.200 1950 483 500 2.07 15.5 7.1 2.6 0.250 1630 450 450 2.06 17.2 5.6 2.2 0.300 1230 407 510 2.01 15th 1.8 1.7 0.310 1040 364 540 • 2.07 17.9 3 2.3 0.400 860 350 443 2.07 14.8 2.2 2.3 0.500 620 320 500 2.05 13.7 6.1 0.560 520 265 420 2.06 18.9 2.1 1.6 0.600 360 295 500 2.03 15.9 3 0.700 478 4.2 0.735 335 1.7 1.8 0.800 326 2.1

It is observed that the Curie temperatures are high above 2000 Gauss, the gyromagnetic resonance line widths are acceptable, and the magnetic and dielectric losses are very low, especially for the material with:

Y = 0.30.

Second group of examples :

One chooses a certain titanium content, whereby the value of the quantity X + Y is fixed, for different increasing ones Values of this quantity one observes the influence of the variable X (zinc content). The results obtained are in the Table 2 summarized.

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X 4πΜ _Β curie Table 2 * eff V tgö 10 ⁴ ΔΗ _Κ Χ + Υ (Gauss) ( ⁰ C) ΔΗ 0.05 2550 475 (Oe) 2.06 17.2 6th 3.1 0.25 0.10 2780 445 420 " 2.05 17.2 4.4 3.1 0.25 0.15 2990 415 380 2.04 16.9 2.6 3.8 0.25 0.20 3160 390 320 2.05 17.1 3.5 3.4 0.25 0.25 3300 365 275 2.04 17.2 3 3.6 0.25 0.25 3050 340 215 2.02 16.6 <1 2.2 0.3 0.21 1930 320 180 2.01 17.7 4.7 1.8 0.5 0.11 900 265 160 2.02 18.7 2.6 1.7 0.7 0.028 435 240 205 2.05 18.4 3.3 1.5 0.8 0.075 530 190 275 2.03 19.4 1.8 0.8 0.125 345 100 133 1.99 19.7 5.4 0.9 86

It is observed that:

1.) For a given titanium content (X + Y), as is the case in the first five lines of Table 2, the magnetization (4ττΜ _σ ) increases with the zinc content (X), but always within certain limits, which changes can easily be explained by the theory of the double, namely tetrahedral and octahedral structure of iron.

2.) For certain purposes, a lower one is used Magnetization value with the lowest possible ΔΗ desired. Enter the last five lines of Table 2 Examples in which this result is achieved with high titanium contents and low zinc substitutions will. At the same time, the Curie temperature drops, which in some cases has practical application possibilities limited.

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• f.

3.) As you can see, you can for the production of ferrites according to the invention with three successive Magnetizations corresponding to orders of magnitude 4ttM " Select sizes with approximately the values given in lines 5, 6 and 7 of table 2, namely:

- for an order of magnitude of 3000: X - 0.25 and Y = 0.05

- for an order of magnitude of 2000: X = 0.20 and Y = 0.30

- for an order of magnitude of 1000: X = 0.10 and Y = 0.60

Third group of examples:

A certain magnetization has been established, which means choosing a certain value for Y, here as Parameter is taken.

The results are summarized in Table 3:

Y (Gauss) Table 3 ΔΗ
(Oe) «Eff 16.5 t
tg6 1O ⁴ X 0.05 2300 ^Ö Curie
( ⁰ C) 385 2.05 16.3 9.6 0.25 0.10 2230 460 305 2.03 16.8 3.3 0.25 0.15 2140 405 270 2.02 16.4 2.5 0.25 0.20 2090 360 200 2.01 18.1 2.5 0.25 0.1875 2050 310 177 2.01 19.1 4.4 0.275 0.285 1100 320 81 2.01 6th 0.45 177

0.55 0.385 530 110 39 2.00 19.9 10

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Recall that the titanium content is given by X + Y. So if you only leave the parameter X vary, the titanium content increases by one titanium ion for each zinc ion added. You therefore work in this case with "bonded" substitutions of zinc and titanium.

It is observed that:

1.) The magnetic moment is in fact roughly constant if one keeps the quantity Y constant. The explanation this phenomenon is obvious when one considers that according to the now classical theory "tetrahedral" iron by zinc and "octahedral" Iron is replaced by titanium.

2.) The line width ΔΗ is reduced especially for the high values of X, which unfortunately results from a decrease the Curie temperature is accompanied. The phenomenon explained in that the zinc replaces "tetrahedral" iron with high magnetocrystalline anisotropy.

The invention is applicable to numerous devices operating at frequencies of 5 GHz or higher, e.g. on phase shifters, circulators and isolators.

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Claims (6)

Patent claims 1) Lithium ferrite that can be used at very high frequencies with spinel structure, characterized by the following general formula: ^Li 0.5 (1 + Y) ^Zn X ^Fe 0.5 (5 - 3Y - 4X) ^Ti X + Y ° 4 ^aBi 2 ° 3 / 3Mn O ₂ (I) where: 0 ^ X <0.4 0.1 <ξ X + Y <0.9 and wherein the bismuth oxide and the manganese oxide are non-stoichiometric Quantity are contained as flux, whereby: 0.001 ^ OL <0.01 0.05 ^ ß> <0.25. 2) ferrite according to claim 1, characterized in that: oc = 0.003 β = 0.14. 3) ferrite according to one of claims 1 or 2, characterized in that: Y - 0.3. 709818/0990 4) ferrite according to one of claims 1 or 2, characterized in that: X = 0.10 Y = 0.60. 5) ferrite according to one of claims 1 or 2, characterized in that: X = 0.20 Y = 0.30. 6) ferrite according to one of claims 1 or 2, characterized in that: X = 0.24 Y = 0.05. 70 9 8 18/0990