US3344072A

US3344072A - Tantalum doped nickel-zinc ferrite

Info

Publication number: US3344072A
Application number: US347176A
Authority: US
Inventors: Akashi Tsuneo; Takamizawa Hideo
Original assignee: Nippon Electric Co Ltd
Current assignee: NEC Corp
Priority date: 1963-02-28
Filing date: 1964-02-25
Publication date: 1967-09-26
Anticipated expiration: 1984-09-26
Also published as: DE1292060B; GB1057774A

Description

Sept. 26, 1967 TSUNEO AKASHI ET AL 3,344,072

TANTALUM DOPED NICKEL-ZINC FERRITE Filed- Feb. 25. 1964 l I 2 Sheets-Sheet l a 7:42 d, (Maz 'Zj Sept. 26, 1967 TSUNEO-AKASH| ET AL TANTALUMv DOPED NICKEL-ZINC FERRITE Filed Feb. 25. 1964 @yx/ff 2 Sheets-Sheet 2 United States Patent C) m l 3,344,072 TANTALUM IBPED NiCKEL-ZNC FERRITE Tsuneo Akaslii and Hideo Takamizawa, Tokyo, Japan,

assignors to Nippon Electric Company Limited, Minatoku, Tokyo, Japan Filed Feb. 25, 1964, Ser. No. 347,176 Claims priority, application Japan, Feb. 28, 1963, .3S/10,780 4 Claims. (Cl. 252-626) The present invention relates to magnetic oxide materials, and particularly to nickel-zinc ferrites which may be used, for example, in communications devices operating at high frequencies.

It is known that nickel-zinc ferrites can be utilized in diverse fields as low-loss magnetic materials suitable for high frequency applications. Nevertheless, the application of nickel-Zinc ferrites in the design and operati-on of coils and transformers for communications use has been found unsatisfactory, primarily because known nickel-Zinc ferrites possess relatively large positive temperature coefficients of initial permeability.

The principal object of the present invention is to provide a nickel-zinc ferrite possessing improved loss characteristics at high frequencies, which ferrite also possesses a temperature coeiiicient of initial permeability which is markedly lower than that of previously known nickel-Zinc ferrite materials.

The nature and objects of the present invention will be more fully apparent from a consideration :of the following detailed description of preferred embodiments thereof, taken in connection with the accompanying drawings illustrating the magnetic characteristics of one embodiment of the nickel-zinc ferrite hereof.

In the drawings:

FIGURE l illustrates the initial permeability fr of a nickel-zinc ferrite as a function of the amount of tantalum pentoxide (Ta205) added to the mixture which, when sintered, produces such ferrite;

FIGURE 2 illustrates the variation of the Q factor aS a function of the percentage of tantalum pentoxide thus incorporated in the composition;

FIGURE 3 shows the dependence of the loss characteristics (1/,uQ) on the percentage of tantalum pentoxide; and

FIGURE 4 shows the dependence of the temperature coefficient of initial permeability (Ap/MEPC.) with the percentage of tantal-um pentoxide,

The objects of the present invention are achieved by providing a nickel-zinc ferrite comprising a sintered mixture of from about 46 to 54 mol percent ferrie oxide, from about 19 to 35 mol percent nickel oxide, from about 11 to 35 mol percent zinc oxide, and from about 0.01 to 4.6 mol percent tantalum pentoxide,

It has been found that, when the indicated amounts of tantalum pentoxide are incorporated with ferrie oxide, nickel oxide and zinc oxide materials prior to sintering, ferrites possessing materially improved loss characteristics and temperature coeiiicients of initial permeability result.

On the other hand, the addition of less than about 0.01 mol percent tantalum pentoxide has only a negligible effect upon the loss characteristics of the resulting ferrite and, when tantalum pentoxide is incorporated in the mixture sintered in amounts in excess of 4.6 mol percent, we have found that the rate of decrease in the initial permeability p is relatively large, resulting in a considerable increase (degradation) of the loss characteristics.

According to another feature :of the present invention it has been determined that the loss characteristics of nickel-zinc ferrites are further improved by incorporating amounts Vof cupric oxide and cobaltic oxide, together with the tantalum pentoxide, in the material sintered to 3,344,072 Patented Sept. 26, 1967 form the desired nickel-zinc ferrite. The c-upric oxide and Vcobaltic oxide adjuvants are incorporated in amounts ranging from 0.1 mol percent to 0.5 mol percent and from 0.05 mol percent to 0.3 mol percent, respectively, of the materials sintered. Surprisingly, the simultaneous addition of the cupric oxide and cobaltic oxide additives further improves the loss characteristics of nickel-zinc ferrites incorporating the same.

The nickel-zinc fer-rites hereof are manufactured by initially combining the several ingredients including the tantalum pentoxide, and the cupric oxide and cobaltic oxide if desired, and milling the mixture by conventional means. The mixture is thereafter heated in air by a presintering operation conducted at about 800 C. for 4 hours, compacted and molded in the conventional manner, and then subjected to a final sinter-ing operation. The final sintering is effected in an oxygen-containing atmosphere at temperatures of from about 1030 C, to 1200 C. for periods of from about 1 to 3 hours.

The following examples rare given for illustrative purposes; it will be appreciated that this invention is not restricted to the nickel-zinc ferrite embodiments illustrated in the examples:

Example] Varying proportions of tantalum pentoxide were admixed with a composition constituted of 50 mol percent ferrie oxide, 22 mol percent nickel ox-ide and 28 rnol percent zinc oxide, and the resulting compositions mixed in a revolving type steel ball mill. Each mixture was subjected to a presintering operation in air at a temperature of S00 C. for four hours, was compacted and molded into the desired shape and was finally sintered in an atmosphere of pure oxygen at a temperature of 1150 C. for one hour.

The values of initial permeability and of the Q factor of the several samples were then measured ata frequency of 3 m-c./s. at room temperature, and changes in the initial permeability with temperature in the temperature range of from 0 to 40 were determined at a frequency of 1 kc./s. in order to determine the values of the temperature coefficient of initial permeability.

The values determined are indicated in the following table:

TABLE I Tantalum pentoxide im Q (1/,uQ,) X106 Ait/MP C.) 10u 1n mol. percent (au-aiu) The values obtained in Table I were then plotted in the characteristic curves of FIGURES 1-4 of the drawing. As will be evident from a consideration of FIGURE l, the initial permeability p reaches a maximum value for ferrites prepared from mixtures containing 0.05 m01 percent tantalum pentoxide; for further increases in the `amount of tantalum pentoxide, the initial permeability decreases sharply at first .and then more gradually.

As Ishown in FIGURE 2 the Q factor increases rapidly with the addition of up to about 0.3 ino-l percent tantalum pentoxide, and then increases gradually with further incremental amounts of the additive.

A comparison of the curves in

FlGURES

1 and 2 readily indicates that, since the proportional increase of the value Q is much larger than the -proportional decrease of the value a, there is a marked decrease (and consequent improvement) in the value 1/ 1Q of the loss characteristic.

Referring to FIGURE 3, the value of the loss characteristic 1/ f/.Q falls off sharply with an increase in the amount of tantalum pentoxide until its concentration reaches 0.3 mol percent, has a minimum value for about 0.8 mol percent, 'and then increases gradually with -a further increase in the amount of the additive agent.

As shown in FIGURE 4, the temperature coeicient of initial permeability falls of rapidly with an increase in the amount of tantalum pentoxide, 4reaching a negative value when about 1.1 mol percent tantalum pentoxide is incorporated in the mixture sintered, and thereafter decreasing steadily with further increases in the amount of tantalum pentoxide. The values of the temperature coefficient of initial permeability thus change over a Wide nange by the addition of tantalurn pentoxide in varying amount, whereby nickel-zinc ferrite samples exhibiting zero, positive, and negative temperature coeicients of initial permeability can be manufactured.

Example 2 Further ferrite compositions Were prepared in the manner described in Example 1, with the exception that the final sintering operation was conducted in air at a tem- TABLE 1I Tantalum pentoxide im Q (1f/1Q) 10s Ait/IH" C 106 in mol. percent (ao-mm) Example 3 TABLE III Tantalum pentoxide p0 Q (1/yQ)X10 Airjli (3.))(10i in mol. percent (ao-one) It is evident from a consideration of Table III that the tantalum pentoxide effects a decrease in the temperature coefficient of initial permeability, irrespective of change inthe sintering conditions employed.

4 Example 4 Nickel-zinc ferrite samples were prepared according to the method described in Example 1, employing mixtures of 50 mol Ipercent ferrie oxide, 25 mol percent nickel oxide, 25 mol percent zinc oxide, and t-antalum pen-toxide in varying proportions. The characteristics of the resulting ferrites were determined :and are indicated in the following table:

TABLE IV Tantalum pentoxde p0 Q, (i/l.tQ,)) 10u Ait/HP C.) X100 in mol. percent (om-140) l 287 29 120 +10. 2 290 29 119 +10. 0 164 y 75 81. 5 +9.3 156 L 8O 80 +4v 3 122 8S 93. 5 +1. 3 102 99 99 2. 0 78 112 114. 5 4. 3

Example 5 TABLE V Tantalum pentoxide u Q, (1//.tQ) 10a Ap,ln2/ C.) 10a in mol. percent (au-a Example 6 TABLE VI Tantalum pentoxide pu Q (l/ILLQJXIOs Air/wl 0.))(10t3 in moi. percent aen-an Example 7 The effects of adding tantalum pentoxide to the mixture of ferrie oxide, nickel oxide and zinc oxide were maintained when the compositions of ferrie oxide, nickel oxide and zinc oxides, varied from 46 mol percent to 54 mol percent, from 19 mol percent to 35 mol percent and from 11 mol percent to 35 mol percent, respectively.

Each of the samples was subjected to a sintering operacupric oxide and from 0.05 to 0.3 mol percent cobaltic tion in pure oxygen at 1150 C. for one hour. oxide.

The characteristics of the resulting ferrites are given 3. A method of manufacturing a nickel-zinc ferrite, inthe following table: comprising TABLE V11 Composition (mol percent) Characteristic Ferrie Nickel Zine Tantalum an Q (1/.LLQ)X1U@ (Apr/2P C.)X10 oxide oxide oxide pentoxide am) Example 8 Ferrite samples were manufactured from the oxide composition utilized in Example 4, to which was added varying proportions of tantalum pentoxide, cupric oxide and cobaltic oxide. The samples were prepared employing a final sintering operation in pure oxygen at a temperature of 1150 C. for a period of one hour. The characteristics of the resulting ferrite samples are given in the following table:

(a) admixing from 46 to 54 mol percent ferric oxide, from 19 to 35 mol percent nickel oxide, from 11 to 35 mol percent zinc oxide, and from 0.01 to 4.6 mol percent tantalum pentoxide; (b) heating the resulting mixture at 800 C. for 4 hours; (c) compacting and molding the mixture into the desired shape; and

(d) thereafter sintering the molded product at a tem- TABLE VIII Additive agents (1n mol. percent) o #o Q (1/14Q) 10 (AfL/#ZI CJXIOS (uu-M) C110 C0203 T3205 o. 5 2. 0 175 59 97 +2. 2 0. 1 173 57 101. 5 +12. 9 o. 05 2. o 191 49 106. 5 2. 9 o. 1 2. 9 119 86 97. 5 0. 8 0.3 152 150 50. 5 +58 0. 3 2. 0 111 114 79 0. 4

It w1ll thus be seen that the mcorporation of tantalum 55 perature of from 1030 to 1200 C. for a perlod of pentoxide in compositions which, upon sintering, provide nickel-zinc ferrites, provides marked improvement in the temperature coefhcients of initial permeability and in the loss characteristics of such ferrites. Since Various changes may, however, be made in the specific ferrite embodiments described above without departing from the scope of the present invention, it is intended that all matter contained in the preceding description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A nickel-zinc ferrite comprising a sintered mixture of from 46 to 54 mol percent fern'c oxide, from 19 to 35 mol percent nickel oxide, from 11 to 35 mol percent zinc oxide, and from 0.01 to 4.6 mol percent tantalum pentoxide.

2. The nickel-zinc ferrite as defined in claim 1, in which said sintered mixture includes from 0.1 to 0.5 mol percent from 1 to 3 hours.

4. The method as defined in claim 3, in which the mixture heated in Step (b) includes cupric oxide and cobaltic oxide in amounts of from 0.1 to 0.5 mol percent and from 0.05 to 0.3 m01 percent, respectively, of said mixture.

References Cited UNITED STATES PATENTS 2,744,873 5/ 1956 Pierkarski 252-625 2,995,517 8/1961 OHara 252-625 3,062,667 11/ 1962 Pierrot et al 252-625 3,062,668 11/1962 Pierrot et a1 252-625 3,208,948 9/1965 Blasse 252-625 FOREIGN PATENTS 632,174 12/1961 Canada.

TOBIAS E. LEVOW, Primary Examiner. R. D. EDMONDS, Assistant Examiner.

Claims

1. A NICKEL-ZINC FERRITE COMPRISING A SINTERED MIXTURE OF FROM 46 TO 54 MOL PERCENT FERRIC OXIDE, FROM 19 TO 35 MOL PERCENT NICKEL OXIDE, FROM 11 TO 35 MOL PERCENT ZINC OXIDE, AND FROM 0.01 TO 4.6 MOL PERCENT TANTALUM PENTOXIDE.