Volume 107, Number 6, November–December 2002Journal of Research of the National Institute of Standards and Technology[J. Res. Natl. Inst. Stand. Technol. 107, 703–718 (2002)]Characterization of Corning EPMA StandardGlasses 95IRV, 95IRW, and 95IRXVolume 107 Number 6 November–December 2002Paul CarpenterAlliance for Microgravity MaterialsScience and Applications,SD46/USRA/NASA,Marshall Space Flight Center,AL 35812andDale Counce and Emily KlukLos Alamos National Laboratory,EES-1 MS D469,Los Alamos, NM 87545andCarol NabelekDepartment of Geological Sciences,University of Missouri,Columbia, MO [email protected] preparation, synthesis, and characteri-zation of Corning trace-element glasses95IRV, 95IRW, and 95IRX by bulkchemical and electron microprobetechniques is discussed. Working values forthe doped elements in the 95-seriesglasses are established. Blank values havebeen determined by both bulk chemicaland electron microprobe analysis, andimportant x-ray interferences are high-lighted. Chemical homogeneity both withina rod cross-section, and along canelength has been documented. These glassesare standard reference mater ials intendedfor use as both primary and secondaryelectron microprobe standards.Key words: Corning; epma; glass; homo-geneity; microprobe; standard; trace ele-ment; eds; 95IRV; 95IRW; 95IRX.Accepted: August 22, 2002Available online: http://www.nist.gov/jres1. IntroductionIn 1971, Art Chodos and Arden Albee, of theDivision of Earth and Planetary Sciences at Caltech,contracted Corning Glass Works1to produce syntheticglasses containing a number of elements at approxi-mately 0.01 mass fraction concentration, with the inten-tion of using these glasses as trace element reference1NIST disclaimer: Certain commercial equipment, instruments, ormaterials are identified in this paper to foster understanding. Suchidentification does not imply recommendation or endorsement by theNational Institute of Standards and Technology, nor does it imply thatthe materials or equipment are necessarily the best available for thepurpose.standards for electron-probe microanalysis (EPMA).The master list of elements was divided into threegroups in order to avoid x-ray peak overlaps within agiven glass standard. Three glasses were subsequentlyproduced, 95IRV, 95IRW, and 95IRX (informallyknown in the microanalysis community as Corning/Caltech glasses GLV, GLW, and GLX, respectively),which were doped with the following elements in aCa-Mg-Al borosilicate glass matrix. Glass 95IRVcontains K, Ti, Cr, Fe, Ce, and Hf, and is green in color.Glass 95IRW contains V, Mn, Co, Cu, Cs, Ba, La, and703Volume 107, Number 6, November–December 2002Journal of Research of the National Institute of Standards and TechnologyTh, and is blue in color. Glass 95IRX contains Ni, Zn,Rb, Sr, Y, Zr, Pb, and U, and is brown in color. Theconcentration of these elements is sufficient to use thestandards for primary calibration by EPMA, and theglasses have since been used for the analysis of a widerange of materials. This paper describes the synthesis,chemical characterization by wet chemical and x-raytechniques, and chemical homogeneity measurementsperformed on these EPMA standard reference materi-als. Information concerning the preparation and earlycharacterization of these standards is based on corre-spondence and documents organized by Art Chodos,and subsequently assumed by Carpenter who has brieflysummarized this early work [1].2. Preparation of Corning 95IRV, 95IRW,and 95IRX GlassesCorning Glass Works had previously produced theSRM 612, 614, and 616 trace element glasses for NIST(then National Bureau of Standards). These glasses werecomposed of a Na-Al silicate matrix, were doped witha maximum level of 5.0⫻10–4of each element, and werebatched in comparatively large 68 kg lots. In contrast,the matrix composition of the 95-series glasses wascarefully chosen to exclude alkali elements (i.e., Na) inmajor concentration, in order to avoid the problem ofalkali migration under the electron beam for applicationas EPMA reference standards. The 95-series glasseswere also doped with a higher level of each element, andeach glass was batched in a 0.91 kg lot and delivered atthe bargain price of $200 per glass. The source mater i-als for each oxide dopant were selected by Corningpersonnel from reagents consistent with production ofother research-grade synthetic glasses, and approxi-mately 1.36 kg of starting material were used to gener-ate each glass. The materials used and the weighed-inquantities of each reagent are listed in Table 1. An errorwas apparently made in the calculation of the amount ofreagent needed to produce a target concentration of 0.01massfraction and as a result, in the process of batchingof the glasses, the amounts of each oxide were nomi-nally 0.0079 mass fraction rather than the intended0.01 mass fraction (there was apparently no error in theweighing process). Because these glasses containsubstantial quantities of the dopant elements, and there-fore associated oxygen would be appropriate in achemical analysis, it was decided early on to report theconcentrations as oxide rather than as the element. Theweighed-in concentrations of all elements are reportedas the most commonly used oxide for purposes ofreporting analyses (rather than the oxide used as sourcematerial), and for this reason the quantities of V, Mn, Fe,Ce, and U are different from the nominal value of0.0079 mass fraction. Notice also that K and Cr werebatched using K2CO3and K2C2O7,andonewouldexpect a correlation to exist between Cr and K in 95IRVfor this reason. No information is currently availableconcerning the oxidation state of elements in the95-series glasses.After batching, each powder was subjected to twocycles of melting and stirring in a Pt-Rh lined containerin a furnace. After these homogenizing steps, a 0.65 cmdiameter glass cane was drawn from the melt and wassubsequently cut into 9 rods, each approximately 13 cmlong, which were then numbered for purposes ofcataloging and tracking. Distribution of the glasses toend-users for use as EPMA standards was in the form of0.65 cm diameter disks cut from the end (i.e.,first drawn) of each cane. Qualitative wavelength-dispersive x-ray fluorescence (WDXRF) x-ray scanswere provided by Corning to document the presence ofthe requested trace elements in each glass (and interest-ingly, also documented the existence of Sr contamina-tion in glasses 95IRX and 95IRW). The
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