1、Designation: C657 93 (Reapproved 2013)Standard Test Method forD-C Volume Resistivity of Glass1This standard is issued under the fixed designation C657; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the dcvolume resistivity of a smooth, preferably polished, glass bymeasuring the resistance
3、to passage of a small amount of directcurrent through the glass at a voltage high enough to assureadequate sensitivity. This current must be measured understeady-state conditions that is neither a charging current nor aspace-charge, buildup polarization current.1.2 This test method is intended for t
4、he determination ofresistivities less than 1016cm in the temperature range from25C to the annealing point of the glass.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-pri
5、ate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Section 5.2. Referenced Documents2.1 ASTM Standards:2D257 Test Methods for DC Resistance or Conductance ofInsulating MaterialsD374 Test Methods for Thickness of
6、 Solid Electrical Insu-lation (Withdrawn 2013)3D1711 Terminology Relating to Electrical InsulationD1829 Test Method for Electrical Resistance of CeramicMaterials at Elevated Temperatures43. Summary of Test Method3.1 The dc volume resistance is measured in accordancewith Test Methods D257, with the s
7、pecimen located in aheating chamber with adequate temperature control, electricalshielding and insulation of the sample leads as described inTest Method D1829.4. Significance and Use4.1 This experimental procedure yields meaningful data forthe dc volume resistivity of glass. It is designed to minimi
8、zespace charge, buildup polarization effects, and surface conduc-tances. The temperature range is limited to room temperatureto the annealing point of the specimen glass.5. Cautions5.1 Thermal emfs should be avoided. Connections involv-ing dissimilar metals can cause measurement difficulties. Evenco
9、pper-copper oxide junctions can produce high thermal emfs.Clean, similar metals should be used for electrical junctions.Platinum is recommended. Welded or crimped connectionsrather than soldered joints avoid difficulties. Specimen elec-trodes shall have sufficient cross section for adequate electric
10、alconductance.6. Apparatus6.1 Resistance-Measuring Devices, and the possible prob-lems associated with them are discussed thoroughly in Section9 and Appendixes A1 and A3 of Test Methods D257. Furtherdiscussion of electrometer circuitry is covered in Annex A1 tothis test method.6.2 Heating Chamber (F
11、ig. 1)For heating the specimen, asuitable electric furnace shall be used. The construction of thefurnace shall be such that the specimen is subjected to auniform heat application with a minimum of temperaturefluctuation. An adequate muffle should be provided to shieldthe specimen from direct radiati
12、on by the heating elements.This may be made of a ceramic such as aluminum oxide orequivalent. A grounded metallic shield shall also be providedwithin the furnace, preferably of silver, stainless steel, orequivalent, to isolate electrically the specimen test circuit fromthe heating element. Furnaces
13、for more than one specimen canbe constructed. The control thermocouple may be located inthe heating chamber outside the metallic shield, as shown inFig. 1, or inside the metallic shield.6.3 Two Flat Contacting Electrodes, smaller in diameterthan the specimen electrodes (see 7.6), shall be used to1Th
14、is test method is under the jurisdiction of ASTM Committee C14 on Glassand Glass Products and is the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved Oct. 1, 2013. Published October 2013. Originallyapproved in 1970. Last previous edition appr
15、oved in 2008 as C657 93 (2008).DOI: 10.1520/C0657-93R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The
16、last approved version of this historical standard is referenced onwww.astm.org.4Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1sandwich the
17、 specimen. Sufficient thickness should be used tomaintain an adequate pressure and to provide heat equalizationbetween the specimen and the contacting electrodes.6.3.1 Fig. 2 shows the specimen setup in the heatingchamber. The bottom electrode shall be placed at the end of ametal rod and shall suppo
18、rt the specimen in the center of thefurnace. The unguarded specimen electrode, No. 3 of Fig. 3,shall be placed in contact with this bottom contacting elec-trode. The top contacting electrode shall be placed on theguarded, specimen electrode, No. 1 of Fig. 3. This topcontacting electrode has leads co
19、nnected to an off-center metalrod. The specimen guard electrode, No. 2 of Fig. 3, shall beconnected to the second off-center metal rod with platinumwire or strap. One end shall be connected to the specimenguard electrode; the other end shall be connected to the metalrod.6.3.2 All rods should be supp
20、orted by insulation outside thefurnace in a cool zone to minimize electrical leakage atelevated temperatures.6.3.3 Fig. 4 shows a top view of the specimen setup in theheating chamber.6.4 A Temperature-Control System should be provided sothat temperature-time fluctuations within the heating chamberar
21、e less than 0.01 T (where T is the temperature in degreesCelsius), during the time interval when resistance measure-ments are made. Two thermocouples should be used foraccurate temperature readings, one in the heating chamber,supplying the emf to the temperature controller and the otheron the guard
22、ring of the specimen. The latter should be used tomeasure the specimen temperature as instructed in the Appa-ratus section (Temperature-Control Device) of Test MethodD1829.7. Test Specimen7.1 The Test Specimens section (Volume Resistance orConductance Determination) of Test Methods D257 describesin
23、detail the specimen requirements. To quote in part, “The testspecimen may have any practical form that allows the use of athird electrode, when necessary, to guard against error fromsurface effects.” For practical reasons, a flat disk or square thatis easy to set up in a furnace box is recommended.
24、Otherconfigurations are possible. The descriptions will apply to flatsamples but can be modified for other configurations. Recom-mended limitations in the diameter of a disk are 40 to 130 mm.This is not a critical dimension as the effective area ofmeasurements is defined by the area of the applied e
25、lectrodes,as stated in 7.7.7.2 As the electrical properties of glass are dependent on thethermal condition of the specimen, this condition should beknown and reported.NOTE 1The glass could be annealed or have had a special heattreatment which should be clearly defined.7.3 Polished surfaces are prefe
26、rable as they permit easiercleaning and application of metallic electrodes.7.4 Thickness of the specimen should be determined withmicrometer calipers, calibrated to 0.01 mm, averaging severalmeasurements on the specimen, as described in Test MethodsD374. Recommended limitations on thickness are from
27、 1.0 to4.0 mm with a maximum variation of 60.1 mm.7.5 There are two main reasons for cleaning a specimen: (1)to assure better contact between an applied electrode and thesurface of the specimen and (2) to remove contaminants thatmay lower the surface resistivity, thereby introducing an errorin the m
28、easurements. If the glass is chemically durable, arecommended cleaning procedure is: (1) trichloroethylene, (2)detergent-water solution, (3) distilled water rinse, and (4)alcohol rinse, air dry. Special surface treatments, poordurability, or the desire to include the effect of surfacetreatment requi
29、re modification or elimination of the cleaningprocedure.NOTE 1Heating elements attached to fused alumina corecovered with baked-on refractory cement.FIG. 1 Heating ChamberC657 93 (2013)27.6 Specimen Electrodes, preferably of gold (vacuum-evaporated), should be applied to clean surfaces in a three-te
30、rminal configuration (Fig. 3). These electrodes should have alow resistance ( 1013cm),this time of electrification may be minutes. If the time becomestoo long (arbitrarily 30 min), it is advisable to raise thetemperature 50C or more to assure an accurate measurement.This avoids the possibility of me
31、asuring a charging current thatis greater than the steady-state current.8.3.2 At Intermediate Temperatures , where the dc volumeresistivities are usually between 109and 1013cm, the timerequired for obtaining the dc resistance of glass is reasonable.This is the temperature range in which reliable dat
32、a can bemost easily obtained. The charging time is short, a steady-statecurrent is readily reached, and the possibility of seeing aspace-charge buildup of the interfacial polarization is remote.8.3.3 At High Temperatures (low resistivities 109cm),the time of electrification is short. The steady-stat
33、e reading isreached quickly. However, an increase in resistance is seenwith time because of the space-charge buildup of the interfacialpolarization. This will result in erroneous data. At thesetemperatures, the dc volume resistance may only be obtainedwith an ac signal. If low-frequency facilities a
34、re not available,it is better to lower the temperature range of the dc measure-ments.8.4 The volume resistance should be obtained at a minimumof four temperatures. For most glasses, these data will lie on astraight line when the log of the resistance or resistivity isplotted versus the reciprocal of
35、 the absolute temperature. If thedata do not fall in a straight line, more data at closertemperature intervals will be needed to determine that portionof the curve which is a straight line. It is only in thisstraight-line portion of the curve that reliable dc resistivity datacan be obtained with a d
36、c potential.8.5 The curve in Fig. 5 illustrates the three temperatureranges discussed. In the low-temperature range, T1, insufficienttime has been allowed to reach a steady-state condition. Thisperiod of time cannot only be impractical, but impossible, if thelimit of the measuring instrument is exce
37、eded. In the high-temperature range, T3, the steady-state condition is reached toorapidly to be seen with a dc potential. Therefore, the tempera-ture range labeled T2is the only range in which reliable dcvolume resistivity data can be obtained. Any exceptions to thiscurve are best ascertained by the
38、 use of low-frequency mea-surements.9. Calculations9.1 Calculate the resistivity of the specimen at each ob-served temperature as follows: 5 R 3 A/h! (2)where: = dc volume resistivity, cm;R = dc volume resistance, ;A = effective area,5cm2= D02/4; andh = effective thickness, cm.9.2 As stated in 8.1,
39、plot the log of the dc volume resistivityagainst the reciprocal of the absolute temperature.9.3 Extrapolation of data to higher or lower temperaturesmay be misleading.5For further refinement of calculation see Appendix X2 (Effective Area ofGuarded Electrode) of Test Methods D257.FIG. 4 Specimen Setu
40、p for Heating ChamberC657 93 (2013)410. Report10.1 Report the following information:10.1.1 Identification of the glass tested,10.1.2 Thermal condition of the specimen,10.1.3 Description of cleaning procedure, if other thanstandard,10.1.4 Manufacturing source and data,10.1.5 Accuracy of the resistanc
41、e measurements,10.1.6 Accuracy of the temperature measurements,10.1.7 Method used, and10.1.8 Plot of these data (8.2).11. Precision and Bias11.1 PrecisionThe precision of this test method is ap-proximately 65%.11.2 BiasBias can be assessed through experimental de-terminations using NIST SRM 624.6ANN
42、EX(Mandatory Information)A1. FACTORS AFFECTING RESISTANCE MEASUREMENTSA1.1 InAppendix X1.9 (Guarding) of Test Methods D257 itis emphasized that errors in current measurements may result ifthe electrometer is shunted by the resistance between theguarded electrode and the guard system. This shunt resi
43、stanceshould be at least 10 to 100 times the input resistance of theelectrometer. In general, electrometers have input resistancesthat vary between 106and 1013. The resistance between theguarded and guard electrodes may vary between 104and 1014.Thus, it is important to know this shunt resistance. Th
44、isresistance can be measured by connecting the battery to theguard electrode and the electrometer to the guarded electrode.The other electrode is connected to ground.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin thi
45、s standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be
46、 reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresp
47、onsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, We
48、st Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rig
49、hts to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).6Available from the Office of Standard Reference Materials, U.S. Department ofCommerce, National Institute of Standards and Technology, Room B311, ChemistryBuilding, Gaithersburg, MD 20899.FIG. 5 Model Curve of dc Volume Resistivity Versus TemperatureC657 93 (2013)5
