D. Krawitz, “Introduction to Diffraction in
`
`Materials Science and Engineering”, Wiley
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`(2001), Ch. 8, pp 215-234
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`QUALITATIVE PHASE ANALYSIS
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`217
`
`Table 3.1. some Subfiies, Number of Entries, and
`Distribution of Quality Marks farthe Inorganic and
`Organic Sections of the Powder Diffraction File
`
`Suhfiles
`
`Ccmtittls
`Common Phases
`CorI'o.<:ivc
`Explosives
`Forensic
`Metals and Alloys
`Minerals
`Pharmaceutical
`Pigment and dyes
`Polymers
`Supercondttctors
`Zeolites;
`
`Ntmzbcr uJ"er1tt't'£sfi)t' tern‘ I-46
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`Inorganic
`Organic
`
`Qmztny of (mfFf(’.\‘
`
`Sluts
`indexed
`Poor quality
`Unknown quality
`Calculated patterns
`Profile t'efinem::nt patterns
`
`Number
`of Entries
`
`315
`3200
`14,! 64
`158
`3012
`12.150
`4278
`122
`1%
`319
`265
`78?
`
`46,035
`18,20!
`
`7557
`|6,468
`l2."r'l6
`23.058
`3659
`9‘)
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`in the international Centre for
`1-1
`Stturcer Adapted from Tilhli.‘
`Difirztction Dam booklttt. Uxirtg the Pmm‘m' l)t‘fi"rrtr.'rt'rm File-.
`
`some entries are also scaled to at reference phase, A1203. for quantitative pttrposcs to
`be discussed below.
`
`A variety of information is; contaitied in the so-called PDF card images, which
`were originally index cards but are now data fields in electronic formats, most notably
`the CD-ROM. The fields of information included are as follows:
`
`I.
`
`PDF number
`
`2. Chemical formula, specimen name, and mineral name
`3 . Strtictural formula
`
`. Expcrimctital information
`. Physical data
`. Opticztldata
`. General comments
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`222
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`QUALITATIVE PHASE ANALYSIS
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`223
`
`Following the eight strongest reflections is the Pearson Symbol Code (PSC). This
`is a three-part notation that gives the (1) crystal system. (2) cell type. and (3) number
`of atoms per unit cell. Thus, for l\laCl, the PSC is cF8, where c is the cubic system,
`F means that the cubic cell
`to number of atoms (4
`
`ofthe Hanawalt index in the presence oi‘ strongly oriented grains is limited; the Fink
`index was an attempt to deal with this.
`
`The Fink Index This method is an alternative search scheme that has been found
`uscfttl when intensity information is not reliable due to factors such as highly ori-
`ented grains and overlapping multiphase patterns, as well as when data are obtained
`by electron diffraction using trattsmission electron microscopes. The eight strongest
`lines are listed, with each of the eight listed first followed by the rest. which are
`cycled in circular fashion. The entries for NaCI are shown in Figure 8.5.
`Retrieval Software A variety of ICDD and independent commercial packages
`are available to facilitate searches. An cxample of the use of the PDF is presented in
`Example 8.1.
`
`Example 8.1 1a'erttt'fica!fo12 afrm Unlcrtoiwz Pm:--tier Usmg the PDF’
`An X-ray powder pattern of an unknown ceramic powder is taken with a
`Debye-Scherrer camera and Cu Kn: radiation. it is shown schematically in Pig-
`urc E8. lta). Measurements of the first 20 diffraction peaks are presented in Table
`138.]. Notice that the first four peaks are measured with less accuracy because
`they are at the lowest angles. Using the Hanawalt or Fink search ittdexcs, the com-
`pound is identified as BaCO3. Entries from each are shown in Figure E8. llb), as
`well as the alphabetical entry. Finally the card image is shown, Figure E8.l(c}.
`According to the PDF card entry, the three most intense lines are at 3.72l6.
`3.6603. and 2.l506 A. with intensities of 100. 50, and 50, respectively. On the
`measured pattern. there are peaks at 3.72 and 3.66 A which have intensity values
`of I00 and 50, respectively. However, the closest measured peak to the one at
`2.1506 :5. on the card image is at 2.146 fit, with an intensity of 29. The overall pat-
`tern correlates, and the compound makes sense in the context of the application
`of the material. The discrepancy maybe due to preferred orientation or measure-
`ment error. This situation is typical of the use of the PDF to identify unknown
`phases. Knowledge ofthe use ofthe material or. better yet. a physical analysis of
`the elements present help greatly in makingjttdgments.
`
`Problems There are a number of possible complications, other than preferred
`grain orientation.
`that can arise when using the PDF for materials science appli-
`cations:
`
`l‘1”itis exatnple comes from the Educational Rcstturcc Ptack-age otthe ICCD.
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