US3644207A

US3644207A - Lithium-titanium-zinc ferrites

Info

Publication number: US3644207A
Application number: US863372A
Authority: US
Inventors: Paul D Baba; Giltan Michael Argentina
Original assignee: Ampex Corp
Current assignee: Ampex Corp
Priority date: 1969-10-02
Filing date: 1969-10-02
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22

Abstract

Microwave ferrites with narrow resonance linewidths, good temperature performance, low losses, low costs, and rectangular hysteresis loops are made from a lithium-titanium ferrite containing a small amount of zinc. In addition, small amounts of copper or manganese can be present in the ferrites.

Description

O Umted States Patent [151 3,644,207 Baba et a1. Feb. 22, 1972 [54] LlTHIUM-TlTANIUM-ZINC FERRITES 3,177,145 4/1965 Brownlow ..252/62.61 X 72] lnvcmors: Paul D. Balm San Carlos; Gman Michael 3,483,126 12/1969 Sara et a1. ..252/62.6 X

Argentina, Belmont, both of Calif.

- Primary Examiner-Tobias E. Levow od t al f. [73] A'sslgnee Ampex Corporation, Redwo C1 y C Assistant Examiner]. Cooper [22] Filed: Oct. 2, 1969 A"omeiy Rbel-t Clay [21] App1.No.: 863,372

[57] ABSTRACT [52] U.S.Cl ..252/62.59, 252/626, 25266226612, Microwave ferrites with narrow resonance newidths, good Int Cl gg temperature performance, 10w losses, low costs, and rectangula! hysteresis loops are made from a lithiummanium ferrite [58] Fleld of Search ..252/62.59, 62.6, 62.61 62.62 containing a Small amount of zinc. In addition, small amounts [56] References Cited of copper or manganese can be present in the ferrites.

UNITED STATES PATENTS 1 Claims, No Drawings 3,065,182 11/1962 Aghajanian ..252/62.6l X 7 LlTI-IIUM-TITANIUM-ZINC FERRITES The invention described herein was made in the course-of a contract with the United States Department of Air Force.

SUMMARY OF THE INVENTION At the present time, garnets are ordinarily employed at microwave frequencies. However, garnets are expensive and have poor temperature performance. Although it has been suggested that ferrites might be used, the losses have been.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following preparative procedure is used in compounding ferrite materials in accordance with the present invention:

Oxides of the constituent metal ions are generally employed when possible. In instances where the chemical instability of the oxide of a particular metal ion causes said oxide to be an impure and unreliable compound, the. anhydrous carbonate of the metal ion is used. The raw materials are weighted out in stoichiometric proportions and are wet mixed for 1 hour or more in a ball mill. The resulting slurry is then dried at around -l C. and the dried raw material mixture is then forced through a standard -mesh screen for ease of handling.

The screened oxide mixture is then loaded into refractory boats. The boats are placed in a box-type furnace, and heated to a predetermined temperature. The exact temperature can vary from 700 to 900 C. The object of this step is twofold: the primary object is to provide sufficient energy to react the oxide mixture to a 70 percent ferrite 30 percent oxide mixture by a solid state reaction. The secondary objective is the simple thermal'decomposition of any carbonates used.

The reacted mixture is generally characterized by a relatively large predominant particle size. Before the mixture can be shaped and sintered into a single phase ferrite body the particle size must be reduced. Ball milling is employed in essentially the same manner as outlined above. The ferrite-oxide slurry is then dried at around 80 C. to a fine powder.

The powder is then mixed with a binder as is well known to those skilled in the art. Wide latitude is permissible in the selection of binders. A typical binder is polyvinyl alcohol.

The addition of the binder can be carried out in the second ball milling step, or in an additional step employing any sort of method facilitating uniform distribution of the substance used as a binder. The binder impregnated powder is then shaped in tool steel dies with enough pressure to facilitate uniform compaction.

The pressed shapes are then sintered at temperatures ranging from 950 to l, 1 50 C. in atmospheres of oxygen or air.

The novel ferrites of the present invention have the following composition.

where 0.05 s w s 0.3

and 0.30 s x s 0.95

0 s s 0.2 0 szs0.2

The following nonlimiting examples illustrate various preferred embodiments of the invention. In the examples, Ex

amples l and 3 illustrate com ositiqns which contain zinc whr e Examples 2 and 4 show su stantially the same composition without the addition of zinc, showing the beneficial effect of the zinc addition.

EXAMPLE 1 A ferrite having the composition where x=0.7, y=0, z=0 and w=0.l was prepared by the above procedure. The reaction step was performed at 900 C. The sintering step was performed at 1,100 C. in an oxygen atmosphere. The ferrite had a coercive force of 2.26 oersteds, a remanence of 709 gauss, a saturation magnetization of 825 gauss, a magnetic loss of 0 decibels per inch, a dielectric loss of 0.7 decibels per inch, a resonance linewidth of 360 oersteds, and a density of 3.64 grams per cubic centimeter.

EXAMPLE 2 Example I contains zinc while Example 2 does not contain zinc. The material of Example 1 is superior because it exhibits a lower coercive force, a higher remanence, a lower magnetic loss, a narrower resonance linewidth, and a higher density than does 2. I

EXAMPLE 3 A ferrite was made where x=0.55, y=0. l, z=0.l and w=0. 1. It has a coercive force of 4.02 oersteds, a remanence of 670 gauss, a saturation magnetization of 915 gauss, a dielectric loss of 0.52 decibels per inch, a resonance linewidth of 375 oersteds, and a density of 4.02 grams per cubic centimeter.

EXAMPLE 4 A ferrite was made where x=0.55, y=0.l, z=0.l and w=0. It had a coercive force of 5.15 oersteds, a remanence of 535 gauss, a saturation magnetization of 661 gauss, a dielectric loss of 0.58 decibels per inch, a resonance linewidth of 550 oersteds, and a density of 3.09 grams per cubic centimeter.

Example 3 contains zinc while Example 4 does not contain zinc. The material of Example 1 is superior because it exhibits a lower coercive force, a higher remanence, a lower dielectric loss, a narrower linewidth, and higher density than does 4.

We claim:

1. A lithium-titanium-zinc ferrite having the formula: