ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR STUDY, DEVELOPMENT, AND PRODUCTION OF FERROSPINELS APPLICABLE TO TUNING OF SEARCH RECEIVERS QUARTERLY PROGRESS REPORT NO. 9, TASK ORDER NO. EDG-6 Period Covering October 1, 1954 to December 31, 1954 E-,ctfrohi:' fDeaie prOp Departient;o Eitri'_. Ehgineering By: D. M. Grimes Approved by: /* k, C. F. Jefferson H. W. Welch, Lr. P. E. Nace Chairman L. Thomassen Steering Committee E. F. Westrumn, Jr. Project 2262 CONTRACT NO. DA-36-039 sc-63203 SIGNAL CORPS, DEPARTIENT OF ThJE ARMY DEPARTMENT OF ARdMY PROJECT NO. 3-99-04-042 SIGNAL CORPS PROJECT 194B January, 1955

TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS iii TASK ORDER iv ABSTRACT vi 1. PURPOSE 1 2. PUBLICATIONS AND REPCRTS 1 3. FACTUAL DATA 2 3.1 Specific Heats 2 3.2 The Effect of Univalent Cations 2 3.3 The System (NixZnyFezFe2O4) 10 3.3.1 Investigation of Reaction Rate 14 3.4 The Effect of Grain Size on Magnetic Properties 14 3.4 Effect of Temperature on Complex Permeability 19 4. CONCLUSIONS 21 >. PROGRAM FOR THE NEXT INTERVAL 22 DISTRIBUTION LIST 23 ii

LIST OF ILLUSTRATIONS Page Fig. la Magnetic Spectra of Na-Ni-Zn-Fe++-Ferrites as 6 a Function of Na-Content Fig. lb Magnetic Spectra of Na-Ni-Zn-Fe++-Ferrites as 7 a Function of Na-Content Fig. 2 Permeability Spectra of an Excess Fe Ni-Zn-Ferrite 9 With Added Na Fig. 3 Magnetic Properties of Ni-Zn-Ferrites vs Firing 11 Temperature Fig. 4 Magnetic Q and Fe++ Content vs Firing Temperature 12 Fig. 5 Magnetic Q vs Fe++ Content 13'Fig. 6 B1 and Q vs Firing Time 15 Fig. 7 Fe++ Content vs Firing Time 16 Fig. 8 Microphotograph of Polished and Etched Surface 18 Fig. 9 Core Properties vs. Temperature 20 TABLES Table I 2 mr Data on Univalent Substituted, Excess Iron, 3 Nickel Zinc Ferrite Table II Magnetic Spectra for Four Univalent Substituted 4 Ferrites Table III Magnetic Spectra for Excess Iron Ferrites 5 Table IV Comparison of Frequency Spectra on Two Similar 8 Cases Table V Mole Fraction of Constituent Oxides by Type 10 Designation Table VI Difference in Mean Grain Length Using Different 18 Polishing Procedures iii

TASK ORDER Title: STUDY, DEVELOPMENT, AND PRODUCTION OF FERROSPINELS APPLICABLE TO TUNING OF SEARCH RECEIVERS Purpose of Task: To further the development of ferrospinels of different incremental permeabilities and low losses, with reference to specific applications of interest to the Signal Corps such as RF tuning units. Procedure: The approach to the general objective will include: a. The preparation, under controlled conditions, of specimens of different compositions; b. The measurement of parameters such as the incremental and initial permeabilities, the saturation inductance, the coercive force and the Q (figure of merit) at various frequencies; c. The interpretation of these magnetic parameters in terms of the composition, reaction temperature, pressure and other conditions in the preparation of the samples; d. The relationship of the solid state properties of the crystallite with the various measured magnetic parameters; e. Theoretical explanations, where possible, for the relationships found in d. above. Reports and Conferences: a. Quarterly Task Order Reports shall be submitted reporting technical detail and progress under this Task Order; b. Task Order Technical Reports of a final summary type are in general desirable and shall be prepared at the conclusion of investigations of each major phase. Such reports shall be prepared as iv

decided in conference between the Electronic Defense Group and the Contracting Officer's Technical Representative in the Countermeasures Branch, Evans Signal Laboratory. Personnel: Electronic Defense Group: Project Physicist: Mr. D. M. Grimes Countermeasures Branch, Evans Signal Laboratory: Project Engineer: Mr. Leon I. Mond Components and Materials Branch, Squier Signal Laboratory: Project Scientist: Dr. E. Both Comments The classification of this Task Order as Unclassified shall not preclude the classification of individual reports according to the information they contain, as determined in conference with the Contracting Officer's Technical Representative. I. O. MYERS Contracting Officer's Technical Representative V

ABSTRACT An investigation of the magnetic properties of basically nickel-zinc ferrites with the addition ofexcess iron and the addition of different weight univalent materials is described. The univalent materials described are potassium, sodium, lithium and nothing. It is found that Q values considerably higher than for plain nickel-zinc ferrites can be obtained in this manner. The study of the correlation between grain size and magnetic properties is continued. A recheck of mean grain size using improved experimental techniques is reported. The temperature dependence of the magnetic Q is reported. vi

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN STUDY, DEVELOPMENT, AND PRODUCTION OF FERROSPINELS APPLICABLE TO TUNING OF SEARCH RECEIVERS QUARTERLY PROGRESS REPORT NO. 9, TASK ORDER NO. EDG-6 Period Covering October 1, 1954 to December 31, 1954 1. PURPOSE The purpose of this report is to summarize the progress made by Task 6 of the Electronic Defense Group from October 1, 1954 to December 31, 1954 on Signal Corps Contract No. DA-36-039 sc-63203. The purpose of the task is to further the development of ferrospinels of different incremental perneabilities and low losses, with reference to specific applications of interest to the Signal Corps such as r-f tuning units. The proposed program of Task EDG-6 was outlined in previous progress reports. Only those items will now be reported which have been worked on during the period. 2. PUBLICATIONS AID REPORTS Professor E. F. Westrum, Jr., and Mr. D. M. Grimes attended the Conference of Ferrimagnetism held at the Naval Ordnance Laboratory, White Oak, Maryland, October 11 and 12, where they read a paper entitled "Low Temperature Heat Capacity Anomaly in Nickel Zinc Ferrite." On November 9, -r. D. M. Grimes visited the Carboloy Corp., Detroit, Michigan, for an inspection of their hot pressing and extruding apparatus used in the manufacture of carbides. _ ~~~~~~~~~~1

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3. FACTUAL DATA 3.1 Specific Heats It is expected that a technical.report will be written during the coming quarter describing the work on specific heat in detail. Therefore, it will not be discussed here. 3.2 The Effect of Univalent Cations The study of the effect of greater than 50 mole % Fe203 and added univalent cations to a nickel zinc ferrite was continued. The series of measurements designated as firing series 5 was designed to find, for the firing procedure used: (a) The effect of additional iron oxide together with additional univalent oxides, computed according to [R20] ={ [Fe203] -0.5 } (b) The effect of a differing [NiO/ZnO] ratio for different values of [Fe203. (c) The effect of substituting nothing, Li, Na or K for R in (a) above. The series was fired at 13750~C for four hours, then cooled at 600C/hr. in an oxygen atmosphere. The results are given in Table I. The tQ product for the E type core increases to the maximum value obtained in the upper left corner (see Table I). For type D the maximum is for[Fe203]= 585, and Ni]= 1.1 or 0.9. Frequency spectra were run using the permeameter for several of the interesting cores. Data are given in Table II for several cores. Two items are worth pointingout: l)in the type A core, 2 drops after passing through a peak of the order of five, 2) the frequency of rapid increase in ~2 is higher than for a 50 mole % Fe203 nickel zinc ferrite. To determine the 2

TABLE I 2 MC DATA ON UNIVALENT SUBSTITUTED, EXCESS IRON, NICKEL ZINC FERRITE de 11 1 Q PQ Code 111 Q I Q Code i1 Q PQ 2O = 1., [Fe203] O.50 [N2]= 1.1, [Fe203] 0.585 [O] 1.1, [Fe203] - 0.620'O J L-ZniOJ' Fe ZnO 101 197 -- -- C-107 110 -- -- C-104 30 101 243 57 13,850 D-107 101 176* 17,800T D-104 47 98 4,600 li04 154* 16,000J 101 226 94 21,200 E-107 78 113 8,800 E-104 8.7 48 420 ]= 0 ~9, [Fe203]= 0.550 0.9, [F203] 0.Fe23O 0620.01 0Zn L i -ZO = ZnO.8 9, Fe20 = 0.620.324 270 40 10,800 A-325 50 50 2,500 A-326 48 170 8,160 ~102 233 30* 6,990 C-108 116 58* 6,700 C-105 41 70* 2,870 ~102 261 47 12,300 D-108 98 145* 14,200 D-105 46 65 2,990 100 165 16,500 ~102 223 70 15,600 E-108 82 118 9,700 E-105 11 38 418 = 0.7, [Fe203] = 0.550 Ni] - 0 07, [Fe2e23] 0.585 [Nn-O ] = 0.7, [Fe203] = 0.620 ~103 234 30 7,000 C-109 100 57* 5,700 C-106 51 73* 3,700 ~103 275 40* 11,000 D-109 118 94 11,100 D-106 46 63 2,900 -103 270 51 13,800 E-106 11.5 35 403 Note: w1 was measured on the permeameter, and the Q was measured on a Q meter. * Showed a drift in Q values. Code: Type A - no univalent cation; Type C - Lithium added; Type D - Sodium added; Type E - Potassium added. 3

TABLE II MAGNETIC SPECTRA FOR FOUR UNIVALENT SUBSTITUTED FERRITES Type Frequency.L1 _12 A-326-1 0.9 46.o --— 0 2.0 48.5.29* 5.0 49.4 -95 10.0 53.1 4.8 18.0 11.2 1.1 D-108-2 2.0 100.0.56* 5.0 99.7 ~.76 10.0 99.0 3.6 18.0 18.1 6.7 E-101-1 0.9 199.5 2.0 266.5 2.5* 5.0 245.5 6.1 10.0 312.7 118.0 18.0 296.6 299.0 E-104-1 0.9 8.2 2.0 8.7.18* 5.0 8.9.14 10.0 8.6.37 18.0 8.9.61 * Q-meter readings.

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN extent to which these effects can be attributed to the excess Fe cations, and how much to the univalent materials, a series of six core types were made around the composition of D-108. The composition is 58.5 m% Fe203, 4.25 m% Na20, 17.65 mb NiO, 19.61 m% ZnO. Sodium variations ranging from none to twice the amount of D-108 were taken. The resulting frequency specrta are shown in Fig. 1. Note that for the D-108 composition, the P2 rise occurs at the highest frequency, and that also for this value the lowest low-frequency pl occurs. To determine the effect of excess iron, samples containing different amounts were made. Table III shows the results. TABLE III MAGNETIC SPECTRA FOR EXCESS IRON FERRITES Sample No. 1 Sample No. 2 Type mFe203 Q1 Q LiQ _1 Q 1iQ A-322 50. 386 4.1 1580 386 4.1 1580 A-323 52.25 521 12 6250 564 11 6200 A-324 55.0 269 40* 10760 287 76* 21800 A-325 58.5 50.1 50* 2500 A-326 62 48.5 168* 8150 47.2 175* 8260 Note: The other data were taken from permeameter. Asterisk indicates data from Q-meter. Firing T = 1375~C Cool 600C/hr. in 02 e -I a 0.9 Table IV shows a frequency spectrum for the two A-326.

g83oi01 tlU 601-99-V Z9ZZ 280 _ 260 8 240 220 8 200 LUI ~ ~ ~ ~ ~ FGI 21606 w II W 140 120 60 0.9 2 4 6 8 0 12 14 16 FREQUENCY (MC) FIG Io MAGNETIC SPECTRA OF No-Ni-Zn-Fe++-FERRITES AS A FUNCTION OF No-CONTENT CURVES NO 4 REPRESENT D-108. i-TH CURVE HAS i/4 TIMES THAT Na CONTENT' 6

gS83dGI HIA 011-99-V Z9ZZ 200 - _________ 180 160 140.120 -7wI00 AS A FUNCTION OF Na-CONTENT (3 80 ~ ~ ~ ~ ~ ~ 7

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE IV COMPARISON OF FREQUENCY SPECTRA ON TWO SIMILAR CASES Core Frequency ~1 Q A-326-1 2.0 48.5 168* 5.0 49.4 52 10.0 53.1 11 18.0 11.2 10 A-326-2 2.0 47.2 175* 5.0 48.5 47 10.0 51.7 12 18.0 12.6 13 Note: Asterisk indicates data taken from Q-meter. The other data were taken from the permeameter. Tests of the sodium-containing cores indicate that firing at a lower temperature of 11500C, followed by slow cooling,yields results nearly the same as for the 20-30 nickel zinc ferrites (see dashed lines of Fig. 2). A series of Na cores were made by placing'them in a furnace at a specified temperature, holding that temperature for one hour, then air quenching. The high frequency characteristics of some of these cores are particularly interesting. An especially interesting example is core D-150-1. The VHF measurements on this core are shown in Fig. 2. The solid curves represent D-150-1, the dashed curves are data on 20-30 Ni-Zn cores. 8

25. FG20 i — F " DPF 51 1 50 100 200 300 400 500 FREQUENCY (MC) FIG 2 PERMEABILITY SPECTRA OF AN EXCESS Fe Ni-Zn-FERRITE WITH ADDED Na DASHED LINES REPRESENT AVERAGE FOR TYPE A CORES

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3.3 The System [NixZnyFezFe204] The following study is being undertaken to investigate the effects of excess iron. Materials with a fixed[l] ratio of 0.9 and differing iron content were made as shown in Table V. TABLE V MOLE FRACTION OF CONSTUIENT OXIDES BY TYPE DESIGNATION Mole Fractions Type NiO ZnQ Fe203 I.2337.2663.5000 II.2219.2465.5316 III.2065.2294.5641 IV.1842.2048.6110 V.1613.1791.6596 This investigation is incomplete. The present trend is described here and a technical report will be issued when the study has been completed. The cores (Types A-327 to A-350) were placed in the furnace and held at a fixed firing temperature. They were left for four hours then air quenched. Figure 3 shows the resulting Pll and Q at 2 mc as measured on a Q-meter. The optimum values of 1l and Q are seento occur in the neighborhood of 12000C. These samples were analyzed for Fe++ content. Fe++ and Q are shown in Fig. 4 for Type V. Note that the change in Fe with T is very rapid and thus shows considerable scatter. The limiting parameter is the temperature control. If the Q is a function of Fe++ only,a plot of Q vs. Fe++ should not show this scatter. Such a plot is shown in Fig. 5. 10

0a~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 Z 200.... I I D 25'O0 Ld FIG 3 * o [.5641 1 ] a. [NiN ~~~~Z 120-~ -~~ C,[Zn] H _, o —o. I__, 1150 1200 1250 1300 1350 FIG3 VS FIRING TEMPERATURE [Fe2O3] AS MOLE FRACTION: 0 [.5641] ]L + [.6110] v [.65961 Q [Ni] [zn]

SG83 81 HAU ~11-99-V Z9ZZ 7 140 6 120 0 I 20 Z LL 0 3- 60 +0 CY 2 - 40 0 0 1100 1200 1300 1400 FIRING TEMPERATURE (0C) FIG 4 MAGNETIC Q AND Fe+ CONTENT VS FIRING TEMPERATURE

ggg3.81 HAN I i 11-99-V Z9?Z2 t10 I00 4~~~~0~ ~ 90 oo 0 ~-~FIG 5 70 30 2 3 4 5 6 Fe++ CONTENT (%) FIG 5 MAGNETIC Q VS Fe CONTENT -13

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 3.3.1 Investigation of Reaction Rate. In order to follow the progress of the solid state reaction as a function of time, the cores were fired by varying the length of time at a given temperature. Figure 6 shows the change in Cl with time on Composition V at two temperatures. It appears that at higher temperatures the Q reaches a maximum very rapidly and then falls off. At sufficiently high temperatures only the fall off can be observed. This is seen in Fig. 6 where Composition I was fired at 12120 and 12620~C. At 12120C, Q is constant for a short time and then decreases. At 1262~C, only the decrease in Q is observed. The change in % Fe++ with time is shown for Composition V at 12120C in Fig. 7. Determinations for other temperatures are in progress. 3.4 The Effect of Grain Size on Magnetic Properties. An initial investigation of possible statistical correlation of magnetic permeability with grain size was reported in Quarterly Progress Report No. 8. It was stated that although the results looked promising enough to warrant further effort, the percentage of the grains pulled out during the polishing technique was quite large. The percentage of grains pulled out was so large that the reliability of the value of mean grain volume obtained was questioned. During the past quarter a study of polishing techniques has been made. The percentage of the material consisting of voids has been drastically reduced. About 50 linear percent of the material consisted of voids under the original polishing technique. This percentage has been reduced to about 25 under the present polishing technique.

360 60... | Q 300 50 -- ~' ~~~ ~~o 1212oC,- 240 0 40 0N2 60 0 v~~~~~~~~~~~~~~~~~~~~~ /~~~~~~~~~~~~~~~~~~~~~~~~~ >-240 3040 9 2 m H 2~~~~~~~~~~~~~~~ 1212~C 3 (1 w Wi120 020 60 10 # 0~~~ 0 ~~~~~30 60 90 2 FIRING TIME (MIN) FIG 6 A4 AND Q VS FIRING TIME 0 121200 v12620

7 0~~~~~~~~ +w 16~~~~~~~~~~~~~~~~~~~~~~~ It 0) 0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~E IN 1,1,1 rO, ~~~~~~~~~~~~~~~~~~~~~~'-I5 N02 010 0 0 %~~~~~~~~~~~~~~~~~~~~~~~~~ + -~~~~~ o~~~~~~~~~~~~a I~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~' LL4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~C 5 I0 20 40 100 200 400 I000 FIRING TIME (MIN) FIG 7 Fe+ CONTENT VS FIRING TIME

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN An attempt was made to fill up the voids in the specimen (which were present after polishing through 4/O paper) with some thermoplastic material so that grains could not be pulled out so easily. This was tried in two ways. In one case the specimen was subjected to a partial vacuum and was then covered with fluid thermoplastic material which was allowed to set. In another case the specimen was remounted with a layer of lucite powder below the specimen. -Neither method gave an appreciable reduction in the amount of voids. Next, a polishing cloth with practically no nap was used, together with several different abrasives, in an attempt to reduce the pulling out of grains The investigations showed that Bursil and gamal cloths, with diamond paste and gamal abrasives, respectively, gave the best results. The new polishing procedure consists of polishing with ligt pressure through 340A, 1, 0, 2/0, 3/0 and 4/0 papers. The initial polishing on wheels was done with 6-diamond paste on Bursil cloth at 600 rpm, and the final polishing with gamal abrasive on gamal polishing cloth at 600 rpm. It was found that continued polishing with gamal abrasive helped reduce voids up to a certain minimum limit after which no appreciable effect was observed. The specimens of the Type A-231 core were polished with diamond paste and gamal abrasives, and were then etched with a mixture of HC1 and SnC12. A photograph of a specimen polished according to the new method, and then etched, is shown in Fig. 8. Table VI gives the difference in mean grain length for each specimen using different polishing procedures. In is the one-dimensional mean grain radius after polishing according to the new technique. lo is the same quantity, using the old polishing technique. Note that with the exception of..... 17....1

MICROPHOTOGRAPH OF POLISHED AND ETCHED SURFACE A-231-14 X I000 18 t; i~ ~~ 44 F~ ~~~~) -~~

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Numbers 5 and 14, all of the mean grain lengths have decreased very slightly. Numbers 5 and 14 show quite radical differences. These differencesI put core No. 14 second in mean grain volume and therefore, increases the correlation between permeability and grain volume. However, core No. 5 is correspondingly moved out of position. In the detailed breakdown of counting procedure, the reason for the increase in grain size in both Numbers 5 and 14 is the occurrence of a much larger number of the very large size grains. 3.5 Effect of Temperature on Complex Permeability In making the Q-meter measurements as a function of frequency, the cores were wound by hand and immediately measured at a 1 me check point. Then after a few minutes to allow the core to reach room temperature, the core was remeasured. In every case the check point fell high on the cdrve —roughly, 4 to 7 percent high. Apparently the core was heated to almost body temperature during the hand winding process. To determine the effect of temperature, the following measurement procedure was established. Initially, the core was measured in air. It was then immersed in oil (at room temperature) and remeasured. No change in L1 or Q resulted. The oil was then heated. Figure 9 shows the results of the three runs. TABLE VI DIFFERENCE IN MEAN GRAIN LENGTH USING DIFFERENT POLISHING PROCEDURES Core No. n-o en 3 -0.0114 1.0074 5 +0.2026 1.0o96 13 -0.0455 1.0232 14 +0.1433 1.1633 18 -0.0390 0.8793 19 -0.0374 0.9226 25 -0.0857 1.1846 * The unit of linear measurement used is 2.1 microns. 19

650 20 90 ~ + IC m LU (0 18 8 600 Q~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ oo 0 16 70 0 0~~~~~~~~~~~~~~~~~~~~ 550 c. o 14 60 co ar J500 < 12 0 50 N ~~~~~C.. 0 LU C LU ~~~~4o w a: ( a. U 10 H4 450 c: <~~~~ < J~~~~~~~~~~~~~~~~~~~~~~ z D Ld CY RAR (~ <8 30 400 + 6 -20 9 _ + + + 1.001a a 350~~~ + + a a ~~50C 4 IC ++ t —r A 4 ~- 10 20 40 60 80 100 120 140 160 TEMPERATURE (OC) FIG 9 CORE PROPERTIES VS TEMPERATURE MEASURED ON Q-METER ARPF NOA L-'.-'4-P

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN ll increases almost linearly with temperature. This agrees with the 1 findings of Harvey, et al. This curve is explained as follows. For iron and nickel, anisotropy constant decreases rapidly to zero as the temperature increases. The magnetostriction constant also decreases with temperature, but more slowly.2 These energies oppose the orientation of the magnetic dipoles away from the zero signal directions. As these energies decrease with temperature, the dipoles are reoriented more easily and the result is a higher permeability. Of course, il is proportional to the saturation magnetization which decreases with temperature, with increasing rapidity, as the Curie point is neared. The net result is a rising permeability as temperature increases until the neighborhood of the Curie point is attained. 41 then decreases rapidly. The rapid decrease in 41 was not observed because the cores were not raised to temperatures approaching the Curie point. 4. CONCLUSIONS The study of the effective addition of univalent cations along with excess iron oxides, shows that the resonant frequency of the material can be materially raised in this way. The permeability spectrum shows that the rapid rise in loss-per-cycle occurs at a frequency at least ten times as high as materials made previously. The question as to whether this is due to the univalent material or the excess iron is partially answered in Section 3.3. A very definite improvement in magnetic properties in the higher frequencies can be obtained by introducing ferrous iron. Apparently the increased eddy current Harvey, Heggi, and Leverenz, RCA Review, XI, 1950, p 359. 2 Zener, Phys. Rev., 96, Dec. 1954, p 1335. 21

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN losses are more than offset by the decrease in other losses. A check on the grain size distribution reported in Quarterly Progress Report No. 8 has been made. The general agreement is quite satisfactory. The polishing procedure has decreased the linear percentage of voids by at least a factor of 2. 5. PROGRAM FOR THE NEXT INTERVAL It is hoped that the specific heat work can be completed during the next quarter. Whether or not the work can be completed will depend upon the difficulty involved in the manufacture of a zinc ferrite with at least nearly all of its Zn located in tetrahedral sites and, at the same time, has suffered no appreciable loss of either zinc or oxygen during the firing process. The study of the effect of ferrous iron on the spinel formation will be continued. An attempt will be made to establish the rate determining reaction of the spinel formation. Is it the compound formation, or is it grain growth? This study will require the use of more precise X-ray measurements. The study of statistical correlation of grain size and grain size distribution with magnetic properties is to be continued. The effects of wire size, the number of turns of wire, and the size of the incremental field measured on the Q-meter is currently being investigated. 22

DISTRIBUTION LIST 1 Copy Director, Electronic Research Laboratory Stanf ord University Stanford, California Attn: Dean Fred Terman 1 Copy Commanding General Army Electronic Proving Ground Fort Huachuca, Arizona Attn: Director, Electronic Warfare Department 1 Copy Chief, Engineering and Technical Division Department of the Army Washington 25, D. C. Attn: SIGJM 1 Copy Chief, Plans and Operations Division Office of the Chief Signal Officer Washington 25, D. C. Attn: SIGOP-5 1 Copy Countermeasures Laboratory Gilfillan Brothers, Inc. 1815 Venice Blvd. Los Angeles 6, California 1 Copy Commanding Officer White Sands Signal Corps Agency White Sands Proving Ground Las Cruces, New Mexico Attn: SIGWS-CM 1 Copy Commanding Officer Signal Corps Electronic Research Unit 9560th TSU Mountain View, California 1 Copy Mr. Peter H. Haas Mine Fuze Division Diamond Ordnance Fuze Laboratories Washington 25, D., C. 75 Copies Transportation Officer, SCEL Evans Signal Laboratory Building No. 42, Belmar, New Jersey FOR - SCEL Accountable Officer Inspect at Destination File No. 22824-PH-54-91(1701) 23

1 Copy H. W. Welch, Jr. Engineering Research Institute University of Michigan Ann Arbor, Michigan 1 Copy Document Room Willow Run Research Center University of Michigan Willow Run, Michigan 11 Copies Electronic Defense Group Project File University of Michigan Ann Arbor, Michigan 1 Copy Engineering Research Institute Project File University of Michigan Ann Arbor, Michigan 24