1、Designation: C 657 93 (Reapproved 2003)Standard Test Method forD-C Volume Resistivity of Glass1This standard is issued under the fixed designation C 657; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 resistan
3、ce 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 fo
4、r the determination ofresistivities less than 1016Vcm 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
5、-priate 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:D 257 Test Methods for DC Resistance or Conductance ofInsulating Materials2D 374 Test Methods for Thickn
6、ess of Solid Electrical Insu-lation2D 1711 Terminology Relating to Electrical Insulation2D 1829 Test Method for Electrical Resistance of CeramicMaterials at Elevated Temperatures33. Summary of Test Method3.1 The dc volume resistance is measured in accordancewith Test Methods D 257, with the specimen
7、 located in aheating chamber with adequate temperature control, electricalshielding and insulation of the sample leads as described inTest Method D 1829.4. Significance and Use4.1 This experimental procedure yields meaningful data forthe dc volume resistivity of glass. It is designed to minimizespac
8、e 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. Evencopper-c
9、opper 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 electricalcond
10、uctance.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 D 257. Furtherdiscussion of electrometer circuitry is covered in Annex A1 tothis test method.6.2 Heating Chamber (Fig. 1
11、)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 radiation by
12、 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 for m
13、ore 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 tosandwich
14、 the specimen. Sufficient thickness should be used to1This 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 May 15, 1993. Published July 1993. O
15、riginallyapproved in 1970. Last previous edition approved in 1988 as C 657 88.2Annual Book of ASTM Standards, Vol 10.01.3Annual Book of ASTM Standards, Vol 15.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.maintain an adequate pr
16、essure 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 support the specimen in the center of thefurnace. The unguarded specimen elec
17、trode, 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 connected to an off-center metalrod. The specimen guard electrode, No. 2 o
18、f 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 supported by insulation outside thefurnace in a cool zone to minimize electr
19、ical 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 chamberare less than 0.01 T (where T is the temperature in degreesCelsius), durin
20、g 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 ring of the specimen. The latter should be used tomeasure the specimen t
21、emperature as instructed in the Appa-ratus section (Temperature-Control Device) of Test MethodD 1829.7. Test Specimen7.1 The Test Specimens section (Volume Resistance orConductance Determination) of Test Methods D 257 describesin detail the specimen requirements. To quote in part, “The testspecimen
22、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. Otherconfigurations are possible. The descriptions will apply to flats
23、amples 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 electrodes,as stated in 7.7.7.2 As the electrical properties of glass a
24、re 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 preferable as they permit easiercleaning and application of metallic electr
25、odes.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 MethodsD 374. Recommended limitations on thickness are from 1.0 to4.0 mm with a maximum variation of 60.1 mm.7.5 There are two m
26、ain 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 measurements. If the glass is chemically durable, arecommended cleanin
27、g procedure is: (1) trichloroethylene, (2)detergent-water solution, (3) distilled water rinse, and (4)alcohol rinse, air dry. Special surface treatments, poor durabil-ity, or the desire to include the effect of surface treatmentrequire modification or elimination of the cleaning procedure.7.6 Specim
28、en Electrodes, preferably of gold (vacuum-evaporated), should be applied to clean surfaces in a three-terminal configuration (Fig. 3). These electrodes should have aNOTE 1Heating elements attached to fused alumina corecovered with baked-on refractory cement.FIG. 1 Heating ChamberC 657 93 (2003)2low
29、resistance ( 1013Vcm),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 measuring a charging current thatis greater than the steady-state
30、current.8.3.2 At Intermediate Temperatures, where the dc volumeresistivities are usually between 109and 1013Vcm, the timerequired for obtaining the dc resistance of glass is reasonable.This is the temperature range in which reliable data can bemost easily obtained. The charging time is short, a stea
31、dy-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 109Vcm),the time of electrification is short. The steady-state reading isreached quickly. However, an increase in resistance
32、 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 are not available,it is better to lower the temperature range of
33、 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 the absolute temperature. If thedata do not fall in a straight
34、 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 dc potential.8.5 The curve in Fig. 5 illustrates the three tempe
35、ratureranges 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 exceeded. In the high-temperature range, T3, the steady-state condi
36、tion 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 use of low-frequency mea-surements.9. Calculations9.1 Calculat
37、e the resistivity of the specimen at each ob-served temperature as follows:r5R 3 A/h! (2)where:r = dc volume resistivity, Vcm;R = dc volume resistance, V;A = effective area,4cm2= p D02/4; andh = effective thickness, cm.9.2 As stated in 8.1, plot the log of the dc volume resistivityagainst the recipr
38、ocal of the absolute temperature.9.3 Extrapolation of data to higher or lower temperaturesmay be misleading.10. 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 thanstanda
39、rd,4For further refinement of calculation see Appendix X2 (Effective Area ofGuarded Electrode) of Test Methods D 257.FIG. 4 Specimen Setup for Heating ChamberC 657 93 (2003)410.1.4 Manufacturing source and data,10.1.5 Accuracy of the resistance measurements,10.1.6 Accuracy of the temperature measure
40、ments,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 624.5ANNEX(Mandatory Information)A1. FACTORS AFFECTING RESISTANCE
41、 MEASUREMENTSA1.1 In Appendix X1.9 (Guarding) of Test Methods D 257it is emphasized that errors in current measurements may resultif the electrometer is shunted by the resistance between theguarded electrode and the guard system. This shunt resistanceshould be at least 10 to 100 times the input resi
42、stance 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. Thisresistance can be measured by connecting the battery
43、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 this standard. Users of this standard are expressly advise
44、d 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 reviewed every five years andif not revised, either re
45、approved 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 theresponsible technical committee, which you may attend. If y
46、ou 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, West Conshohocken, PA 19428-2959,United States. Individua
47、l 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).5Available 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 TemperatureC 657 93 (2003)5
