ASTM A893/A893M-03

Standard Test Method for Complex Dielectric Constant of Nonmetallic Magnetic Materials at Microwave Frequencies

SIGNIFICANCE AND USE
This test method can be used to evaluate batch type or continuous production of material for use in microwave applications. It may be used to determine the loss factors of microwave ferrites or help evaluate absorption materials for use in microwave ovens and other shielding applications.
The values obtained by use of this practice can be used as quality assurance information for process control, or both, when correlated to the chemistry or process for manufacturing the material.
SCOPE
1.1 This test method covers the measurement of the complex dielectric constant of isotropic ferrites for extremely high-frequency applications.
1.2 The values and equations in customary (cgs-emu and inch-pound) or SI units are to be regarded separately as standard. Within this standard, SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.3  This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 30-Sep-2003
• ICS: 29.030 - Magnetic materials
• Technical Committee: A06 - Magnetic Properties
• Drafting Committee: A06.01 - Test Methods

Relations

• Replaces: ASTM A893-97 - Standard Test Method for Complex Dielectric Constant of Nonmetallic Magnetic Materials at Microwave Frequencies
• Effective Date: 01-Oct-2003
• Replaced By: ASTM A893/A893M-03(2008) - Standard Test Method for Complex Dielectric Constant of Nonmetallic Magnetic Materials at Microwave Frequencies
• Effective Date: 01-May-2008
• Referred By: ASTM D2520-21 - Standard Test Methods for Complex Permittivity (Dielectric Constant) of Solid Electrical Insulating Materials at Microwave Frequencies and Temperatures to 1650 °C
• Effective Date: 01-Oct-2003

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:A893/A893M–03
Standard Test Method for
Complex Dielectric Constant of Nonmetallic Magnetic
1
Materials at Microwave Frequencies
ThisstandardisissuedunderthefixeddesignationA893/A893M;thenumberimmediatelyfollowingthedesignationindicatestheyear
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.3 The specimen is in the form of a rod and is placed
parallel to the microwave electric field in a region of substan-
1.1 This test method covers the measurement of the com-
tially uniform electric and zero microwave magnetic fields.
plex dielectric constant of isotropic ferrites for extremely
The perturbation theory requires that the diameter of the
high-frequency applications.
samplerodbesmallcomparedtoonequarterofthewavelength
1.2 The values and equations in customary (cgs-emu and
of the microwave radiation in the specimen. Estimation of this
inch-pound) or SI units are to be regarded separately as
wavelengthrequiresknowledgeofthepermittivity, e= ke ,and
0
standard. Within this standard, SI units are shown in brackets.
permeability, µ, of the specimen under the conditions of
Thevaluesstatedineachsystemmaynotbeexactequivalents;
measurement. The wavelength, l, in the specimen is given by
therefore,eachsystemshallbeusedindependentlyoftheother.
the equation:
Combiningvaluesfromthetwosystemsmayresultinnoncon-
1/2
formance with the standard.
l51/f 8~µe! (2)
1.3 This standard does not purport to address all of the
For many ferrites, µ may be taken equal to µ , the perme-
0
safety concerns, if any, associated with its use. It is the
ability of empty space, without serious error. The permittivity,
responsibility of the user of this standard to establish appro-
e, is determined by measurement as described below; after
priate safety and health practices and determine the applica-
obtaining a value of e, it is necessary to ascertain with the aid
bility of regulatory limitations prior to use.
of Eq 1 that the sample diameter is sufficiently small.
2.4 This test method is not suitable for materials with loss
2. Summary of Test Method
tangents$0.1, with the loss tangent defined as tan d= k 9/k 8.
2.1 In an isotropic dielectric medium with a steady electric
2.5 Theresultsoftheperturbationtheorycalculationmaybe
field, E, the electric displacement, D, is given by the equation:
expressed in the form:
D 5 ke E (1)
0
o i o 2
df/f 5 @2~k 21!|Miv E E dv#/2|Miv ~E ! dv (3)
s c
where:
where:
e = permittivity of free space and
0
f = f 8+jf8/2Q;
k = dielectric constant. If the medium is subjected to an
Q = loaded Q of the cavity;
alternating electric field, the electric displacement is
v = specimen volume contained within the cavity,
s
not necessarily in phase with the field. This fact may
3 3
in. [mm ];
beexpressedmathematicallybytaking kasacomplex
3 3
v = cavity volume, in. [mm ]; and
c
quantity. If we write k= k 8− jk 9, the imaginary part,
E = microwave electric field strength.
k9, determines the dissipation in the medium.
The superscript o refers to fields in the empty cavity and the
2.2 This test method uses a cavity perturbation technique as
superscript i refers to fields inside the specimen.
a means of separating electric from magnetic effects. Quanti-
2.6 Aspecific cavity suitable for this test method is a TE
10n
ties that must be measured are the resonance frequency, f,of
2
rectangular cavity, where n is odd. With the rod running
the cavity with and without the sample, the loaded Q of the
completely across the cavity at the center, Eq 2 for df/f can be
cavity with and without the specimen, and the cavity and
reduced to the following:
specimen dimensions.
df 8/f 8522~k 8 21!~v /v !; d ~1/Q! 54k 9~v /v ! (4)
s c s c
1
This test method is under the jurisdiction of ASTM Committee A06 on
2
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest See, for example, Montgomery C. G., Ed., Technique of Microwave Measure-
Methods. ments, McGraw-Hill Book Co., Inc., New York, 1947, pp. 294–295; Bronwell and
Current edition approved Oct. 1, 2003. Published November 2003. Originally Beam, Theory and Application of Microwaves, McGraw-Hill Book Co., Inc., 1947,
approved in 1963. Last previous edition approved in 1997 as A893–97. pp. 368–337.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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A893/A893M–03
df and d(1/Q) are, respectively, the difference in the cavity 5.3 The input and output lines of this cavity shall be made
resonant frequency with and without the specimen and the to appear as matched loads by the appropriate use of pads or
differenceinthere
...