NATL INST. OF STAND & TECIA UNITED STATES DEPARTMENT OF COMMERCE

PUBUCATION

AlllDb 3bQS71

^/^^S^ NBS SPECIAL PUBLICATION 260-47

Stdfidcird Reference Materials:

ELECTRICAL RESISTIVITY OF

ELECTROLYTIC IRON, SRM 797,

AND AUSTENITIC STAINLESS STEEL,

SRM 798, FROM 5 TO 280 K

U.S. ^^^^H

EPARTMENT

OF ^^^^1

COMMERCE ^^^^H

National ^/S^^

Bureau 5^

of lOO

Standards U^J

C.2-.
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Bureau of Standards

$ DEC 1974 Standard Reference Materials:

0?)DD ELECTRICAL RESISTIVITY OF ELECTROLHIC IRON, SRM 797,

7,^ Y

AND AUSTENITIC STAINLESS STEEL, SRM 798, FROM 5 TO 280 K

^ ^ J. G. Hust

Cryogenics Division

Institute for Basic Standards

• $ » National Bureau of Standards » » Boulder, Colorado 80302

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Diredor

Issued February 1974
Library of Congress Catalog Number: 74-600002

National Bureau of Standards Special Publication 260-47

Nat. Bur. Stand. (U.S.), Spec. Publ. 206-47, 20 pages (Feb. 1974)

CODEN: XNBSAV

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CONTENTS

Page

1. Introduction 2

2. Apparatus and Data Analysis 2

3. Specimen Characterization 3

4. Results 3

5. Summary 10

6. Footnotes and References 10

Appendix I U

LIST OF TABLES

Table 1. Parameters, b^, of equation (1) 4

Table 2. Calculated values of electrical resistivity for SRM's

797 and 798 . . 5

LIST OF FIGURES

Figure 1. Experimental electrical resistivity deviations from calculated

values (equation 1) for SRM 797 6

Figure 2. Experimental electrical resistivity deviations from mean

values of resistivity for three specimens of SRM 798 7

Figure 3. Calculated values of electrical resistivity for SRM 797 .... g

Figure 4. Calculated mean values of electrical resistivity for SRM 798. 9

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vi
Electrical Resistivity of Electrolytic Iron,

SRM 797, and Austenitic Stainless Steel,

SRM 798, from 5 to 280

J. G. Hust

Cryogenics Division, NBS Institute for

Basic Standards, Boulder, Colorado 80302

Electrical resistivity data are presented for characterized electrolytic

iron, SRM 797, and austenitic stainless steel, SRM 798, at temperatures from

5 to 280 K. Resistivities at ice and liquid helium temperatures were determined for 22 randomly selected iron specimens and the same number of steel

specimens. These data indicate that the effect of material variability is about

1% for each of these SRM's.

Key words: Austenitic stainless steel; cryogenics; electrical resistivity;

electrolytic iron; Lorenz ratio; standard reference material.

This work was carried out at the National Bureau of Standards, Boulder,

Colorado, under the sponsorship of NASA-Space Nuclear Systems Office,

Cleveland, Ohio and the National Bureau of Standards Office of Standard

Reference Materials (NBS-OSRM), Washington, D. C.

1
1 . Introduction

The research reported here is part of a larger program to establish

several thermal conductivity and electrical resistivity standard reference

materials. Several materials are needed to cover wide ranges of conductivity

and resistivity. In earlier publications^'^ of this series, thermal conductivity

data were presented for SRM 734 and 735. It has been decided that low temperature electrical resistivity data on these materials would be useful for two

reasons. The characterization of the thermal conductivity specimens is improved

with electrical resistivity data. Standards of electrical resistivity are useful

for calibration and comparisons of the many existing apparatus. Although

electrical resistivity measurements are generally considered routine, unsuspected systematic errors may be detected readily through the use of these

Standard Reference Materials, SRM's,

The basic characteristics of an SRM are that it be: (a) stable and re- producible under the conditions of use, (b) uniform throughout a single specimen, (c) similar in property value to that of the rq.aterials to which it will be

applied, (d) readily machined and fabricated to appropriate size and shape,

(e) chemically inert with its environment, and (f) useable over a wide temperature range. The iron and steel reference materials satisfy these criteria

reasonably well.

2. Apparatus and Data Analysis

A detailed description of this apparatus and the methods of data analysis

have been given by Hust, et al.* Briefly, the measurement is done by a standard 4 terminal potentiometric method on a 23 cm long cylindrical rod.

The diameter of the rod is dependent upon its conductivity with a maximum

diameter of about 2.5 cm. The electrical resistivity data were taken simultaneously with the thermal conductivity data on the same specimen with a single

apparatus. Data were taken in the presence of temperature gradients along

the specimen but the data analysis was performed so as to include the effect of

these gradients.

2
Tlie experimental data are represented by arbitrary functions over

the entire temperature range and smooth tables are generated from these

functions. The number of terms used to represent each of the data sets is

optimized, through the use of orthonormal functions, so that none of the

precision of the data is lost by underfitting, nor are any unnecessary

oscillations introduced by overfitting.

3. Specimen Characterization

Details of specimen characterization have been given by Hust and

Sparks ^'^ and will not be repeated here. The results of these measurements showed a material resistivity variability of about 1% for both SRM

797 and 798. Specimens of these SRM's should therefore be used only for

standardization to 1%. (See Appendix I for variability data and proper heat

treatment of these SRM's.)

4. Results

The electrical resistivity of one specimen of SRM 797 was measured

from 6 to 280 K. Three specimens of SRM 798 were measured from 5 to

280 K. These data were functionally represented with the following equation:

m

p = y b. [inT]^'^ L ^ ^ (1) i= 1

P is electrical resistivity in ohm meters and temperatures, T, are in

kelvin based on the lPTS-68 scale above 20K and NBS P2-20 (1965) scale

below 20 K. The parameters, b^ determined by least squares, are presented

in table 1. Further details of the fitting procedure are described by Hust,

et al.*^ The deviations of the experimental data from this equation are given

in figures 1 and 2. Values of P, calculated from equation 1, are presented

in table 2 and figures 3 and 4,

3
A detailed error analysis for this system has been presented previously by Hust, et al.''' Based on this analysis of systematic and random

errors, the measurement uncertainty estimate (with 95% confidence) is

0.25% of the resistivity. ^

Table 1. Parameters, b^ , of equation (1)

i SRM 797 SRM 798

1 1. 52995843 X 10"^ 8. 51517313 X

10-"^

2 -6. 57221842 X 10'^ -8. 57069352 X

10-"^

3 1.28083500 X 10'* 1. 18184172 X 10-®

4 -1 . 50027718 X 10"* -8. 87557838 X

10-"^

5 1. 17942860 X lO"'* 3. 97914551 X

10""^

6 - 6. 57740194 X 10"^ -1. 09135708 X

10-"^

7 2. 67952461 X 10"^ 1. 78713688 X 10-^

8 -8. 08115141 X 10-^ -1. 59617291 X 10"^

9 1. 80581011 X 10"^ 5. 97187252 X lO'H

10 -2.95519976 X

10--^

11 3. 44469418 X lo-Q

12 -2. 70952664 X 10"^

13 1. 28939040 X

10-1°

14 -2. 80388287 X

10-12

4
Table 2. Calculated values of electrical resistivity

for SRM's 797 and 798

Resistivity

Temperature (n Cl m)

(K) SRM 797 SRM 798

5 -- 593

6 3.87 593

7 3.87 593

8 3.85 593

9 3.85 593

10 3.85 593

12 3.87 593

14 3.89 593

16 3.90 593

18 3.90 593

20 3.92 593

25 3.99 593

30 4.10 594

35 4.26 595

40 4. 50 597

45 4.84 598

50 5.28 601

55 5.85 604

60 6.54 607

65 7.37 610

70 8.32 613

Resistivity

Temperature (n m)

(K) SRM 79 7 SRM 798

75 9.38 617

80 10.56 621

85 11.88 625

90 13.27 629

95 14.76 634

100 16.32 638

110 19.69 647

120 23.30 656

130 27.07 665

140 31.0 674

150 35.0 683

160 39. 1 692

170 43.2 701

180 47.5 710

190 51.8 718

200 56.1 727

220 65.2 743

240 74.4 760

260 84. 2 776

280 94.3 791

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Figure 3. Calculated values of electrical resistivity for SRM 797

.8
0 80 ! 60 240 320

TEMPERATURE,

K

Figure 4, Calculated mean values of electrical resistivity for SRM 798

9
5 . Summary

We have established low temperature electrical resistivitystandard reference data for electrolytic iron, SRM 797, and austenitic

stainless steel, SRM 798, at temperatures from 5 to 280 K. These

data were fitted to an feinpirical equation which was used to generate

tabular values of resistivity at integer temperatures. Material

variability affects electrical resistivity by about ± 1% and'measurement

uncertainty is estimated to be about 0. 25%.

6. Footnotes and References

[ 1] Both SRM's 797 and 798 are available in the form of rods of three

different lengths. SRM's 797-1 and 798- 1 are rods 5 cm (2 in. ) lon^

and 0. 64 cm (1/4 in. ) diameter; SRM's 797-2 and 798-2 are rods

10 cm (4 in. ) long; and SRM's 797-3 and 798-3 are rods 15 ccn (6 in

long. Longer continuous lengths can be obtained by special order.

These SRM's may be ordered from the Office of Standard Reference

Materials, National Bureau of Standards, Washington, DC 20234.

[2] Hust, J, G. and Sparks, L. L. , Thermal Conductivity of Electrolyt

Iron, SRM 734, from 4 to 300 K, Nat. Bur. of Stand. Spec. Pub.

260-31, 19 pp. (Nov. 1971).

[3] Hust, J. G, and Sparks, L, L. , Thermal Conductivity of Austenitic

Stainless Steel, SRM 735, from 5 to 280 K, Nat. Bur. of Stand. Spe

Publ. 260-35, 15 pp. (Apr. 1972).

[4j Hust, J. G, , Powell, R. L. , and Weitzel, D. H. , Thermal

Conductivity Standard Reference Materials from 4 to 300 K.

I. Armco Iron: Including Apparatus Description and Error

Analysis, J. Res. Nat. Bur. Stand. (U.S.), 74A (Phys. and

Chem. ) No 5, 673-690 (1970).

10
Appendix I Electrical Resistivity Variability

An extensive resistivity variability study was conducted on SRM-797

the object being to determine if it could be heat treated in such manner that

the electrical resistivity would be the same for each specimen. This was

achieved with a 2-hour, 1000 °C anneal in either a vacuum or helium atmosphere. The results of this study are shown as residual resistivity ratios

below. The ratio given is resistivity at 273. 15K to resistivity at 4K. Specimens labled C2T, A6L,, C5L,, AIL, and A5T were obtained from 1/4" diameter rods; the remaining specimens were machined from 1-1/4" rods.

Based on the 63 residual residual resistivity ratio measurements made on

these specimens in various stages of heat treatment, the following is

concluded: The large 1-1/4" diameter specimens are significantly different

in residual resistivity ratio from the smaller 1/4" diameter specimens in

the as received condition. The ratio of the small rods is 22.01 ± 0. 20

while the ratio of the larger rods is 19.5 2 ± 0.44.

Various heat treatments were tried to remove the differences in ratio

of the two sets of rods. After SOO'C for 1 hour the ratios increased but were

still different (small rods = 23. 53 ± 0.20; large rods = 22.14 ± 0.34). Raising

the temperature to 1000°C for 2 hours produced rods which are indistinguishable, (small rods = 23. 39 + 0. 28; large rods = 23. 39 ± 0. 20; all rods =

23. 33 ± 0.24). The variation shown is 2s, where s is the estimated

standard deviation, and includes material and measurement variability. In

order to study the possibility of a change in these ratios with age, some of

the rods were measured after about 50 days and again after 3 years; no

significant change was detected after 50 days but in 3 years a 4% increase in

RRR occurred. Heating to 400 °C for 2-1/2 days changed the ratio to 24.94 ±

0. 26 with no difference between the large and small rods when the first

measurements were made during 1970. However, in 1973 a similar heat

treatment produced a much smaller change. This is not understood.

11
After performing further anneals to obtain a better understanding of the

aging phenomena, it appears clear that our earlier selected anneal procedure

was proper in that we obtained the RRR value corresponding to the stabilizing

condition of this iron. However, we were not aware at the time of the importance of the cooling rate of the furnace. At that time we used a rather massive furnace which cooled rather slowly. With the smaller furnace used in

these later measurements, a hold of at least two hours at 800°C is necessary

to stabilize this iron. After this heat treatment, heating the specimens to

intermediate temperatures does not significantly affect the residual resistivity

ratio. These measurements show that SRM 797 can be used as an electrical

resistivity standard below room temperature with a variability of about 1%

if annealed first at 1000 °C for 2 hours and then 800 °C for 2 hours.

U.S. G.P.O.: 1974-542-654/140

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FORM NB5-114A (1-71) u.^. DEPT. OF COMM. ' 1. PUBLICATION OR REPORT NO. 2, Gov't Accession

BIBLIOGRAPHIC DATA ._ No. SHEET _ NBS SP 260-47

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Electrical Resistivity of Electrolytic Iron, SRM 797, and

Austenitic Stainless Steel, SRM 7 98, frem 5 to 280 K

5. Publication Date February 1974

6. Performing Organization Code

7. AUTHOR(S)

J. G. Hust

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS , Boulder Labs

DEPARTMENT OF COMMERCE

Boulder, Colorado 80302

•>

10. Project/Task/Work Unit No. 2756767

11. Contract/Grant No. N. A.

12. Sponsoring Organization Name and Address NASA-Space Nuclear Systems Office

Cleveland, Ohio and the National Bureau of Standards Office

of Standard Reference Materials (NBS-OSRM), Washington,

D. C.

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Electrical resistivity data are presented for characterized electrolytic iron, SRM 797,

and austenitic stainless steel, SRM 798 , at temperatures from 5 to 280 K. Resistivities at ice and liquid helium temperatures were determined for 22 randomly selected

iron specimens and the same number of steel specimens. These data indicate that the

effect of material variability is about 1% for each of these SRM's.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Austenitic stainless steel; cryogenics; electrical resistivity; electrolytic iron;

Lorenz ratio; Standard reference material.

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NBS TECHNICAL PUBLICATIONS

PERIODICALS JOURNAL OF RESEARCH reports National Bureau of Standards research and development in

physics, mathematics, and chemistry. Comprehensive

scientific papers give complete details of the work,

including laboratory data, experimental procedures,

and theoretical and mathematical analyses. Illustrated with photographs, drawings, and charts. Includes

listings of other NBS papers as issued.

Published in two sections, available separately:

• Physics and Chemistry (Section A)

Papers of interest primarily to scientists working in these fields. This section covers a broad range of physical and chemical research, with major emphasis on standards of physical measurement, fundamental

constants, and properties of matter. Issued six times a year. Annual subscription: Domestic, $17.00; Foreign, $21.25.

• Mathematical Sciences (Section B)

Studies and compilations designed mainly for the mathematician and theoretical physicist. Topics in mathematical statistics, theory of experiment design,

numerical analysis, theoretical physics and chemistry,

logical design and programming of computers and

computer systems. Short numerical tables. Issued quarterly. Annual subscription: Domestic, $9.00; Foreign,

$11.25.

DIMENSIONS, NBS

The best single source of information concerning the Bureau's measurement, research, developmental, co- operative, and publication activities, this monthly

publication is designed for the layman and also for the industry-oriented individual whose daily work

involves intimate contact with science and technology —for engineers, chemists, physicists, research managers, product-development managers, and company

executives. Annual subscription: Domestic, $6.50; Foreign, $8.25.

NONPERIODICALS Applied Mathematics Series. Mathematical tables, manuals, and studies. Building Science Series. Research results, test methods, and performance criteria of building materials, components, systems, and structures. Handbooks. Recommended codes of engineering

and industrial practice (including safety codes) de- veloped in cooperation with interested industries,

professional organizations, and regulatory bodies. Special Publications. Proceedings of NBS conferences, bibliographies, annual reports, wall charts,

pamphlets, etc. Monographs. Major contributions to the technical

literature on various subjects related to the Bureau's

scientific and technical activities. National Standard Reference Data Series.

NSRDS provides quantitative data on the physical

and chemical properties of materials, compiled from

the world's literature and critically evaluated. Product Standards. Provide requirements for sizes, types, quality, and methods for testing various industrial products. , These standards are developed co- operatively with interested Government and industry groups and provide the basis for common understanding of product characteristics for both buyers and

sellers. Their use is voluntary.

Technical Notes. This series consists of communications and reports (covering both other-agency and

NBS-sponsored work) of limited or transitory interest. Federal Information Processing Standards

Publications. This series is the official publication

within the Federal Government for information on

standards adopted and promulgated under the Public

Law 89—306, and Bureau of the Budget Circular A—86

entitled. Standardization of Data Elements and Codes

in Data Systems.

Consumer Information Series. Practical information, based on NBS research and experience, covering areas of interest to the consumer. Easily understandable language and illustrations provide useful background knowledge for shopping in today's tech- nological marketplace.

BIBLIOGRAPHIC SUBSCRIPTION SERVICES

The following current-awareness and literature-survey bibliographies are issued periodically by the Bureau

Cryogenic Data Center Current Awareness Service (Publications and Reports of Interest in Cryogenics).

A literature survey issued weekly. Annual subscription: Domestic, $20.00: foreign, $25.00.

Liquefied Natural Gas. A literature survey issued quarterly. Annual subscription: $20.00. Superconducting Devices and Materials. A literature survey issued quarterly. Annual subscription: $20.00. Send subscription orders and remittances for the preceding bibliographic services to the U.S. Department

of Commerce, National Technical Information Service, Springfield, Va. 22151. Electromagnetic Metrology Current Awareness Service (Abstracts of Selected Articles on Measurement

Techniques and Standards of Electromagnetic Quantities from D-C to Millimeter-Wave Frequencies). Issued monthly. Annual subscription: $100.00 (Special rates for multi-subscriptions). Send subscription order and

remittance to the Electromagnetic Metrology Information Center, Electromagnetics Division, National Bureau

of Standards, Boulder, Colo. 80302. Order NBS publications (except Bibliographic Subscription Services)

from: Superintendent of Documents, Government Printing Office, Washington, D.C. 20402.
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