1. Phase Identification by X-ray Diffraction
(From Chapter 9 of Textbook 2)

2. Powder Diffraction Methods
• Qualitative Analysis
– Phase Identification
• Quantitative Analysis
– Lattice Parameter Determination
– Phase Fraction Analysis
• Structure Refinement
– Rietveld Methods
• Structure Solution
– Reciprocal Space Methods
– Real Space Methods
• Peak Shape Analysis
– Crystallite Size Distribution
– Microstrain Analysis
– Extended Defect Concentration

3. 1930’s
Hanawalt, Rinn and Frevel (Dow Chemical): diffraction
data on about 1000 compounds
JCPDS, ICDD: Joint Committee on Powder Diffraction
Standards; was renamed International Center for
Diffraction Data.
Hanawalt Method: (Grouping scheme)
values of the three strongest lines (d1, d2, d3) and
intensities (I/I1)

4. three strongest lines
File
number
lowest-angle line
Chemical formula and
name of substance
Special
symbol
data on
diffraction
method used
crystallographic
data
optical and
other data
data on
specimen
diffraction pattern

5. Special symbols give extra information:
*: well-characterized chemistry, quantitative measure
of intensity, high-quality d-spacing data (3 to 4
significant digits, no serious systematic errors)
i: reasonable range and even spread of intensity,
“sensible” completeness of the pattern, good d-spacing
data (3 significant digits)
o: low precision data, possible multi-phase mixture,
possible poor chemical characterization
c: powder pattern calculated from structural parameters

6. Procedure (1) Locate proper d1 group
(2) Find the closest match to d2 (±0.01 Å)
(3) Follow by matching d3
(4) Compare relative intensity
(5) Good agreement in search manual 
locate the proper PDF card 
compare the d and I/I1values of all the peaks

7. Examples: unknown pattern from measurement:
strongest lines in the powder pattern:
d1 = 2.82; d2 = 1.99; d3 = 1.63

8. Portion of the ICDD Hanawalt search manual:
d1 = 2.82; d2 = 1.99; d3 = 1.63
Matched, turn to card number 5-628

9. Very weak K
(220) plane
higher
Intensity?
Absorption
effect
Discrepancies!!
2×2.18×sin = 1.54  = 20.68o
2×d×sin 20.68o = d = 1.97
Not
listed

10. Identification of Phases in Mixtures
Examples: pattern of unknown d:
I/I1: d:
I/I1:
No substance matching (d1:2.09; d2:2.47; d3: 1.80) all
together  probably a mixture
Assume: d1 and d2 not the same phase.
d1 and d3 the same phase  find Cu
Check the Pattern of Cu: d:
I/I1:

11. Remainder of pattern of unknown:
I/I1:
I/I1:
Normalized
Following the steps of searching again  Cu2O

12. Overlapped diffraction lines  carefully subtract the
intensity from the already identified phases to help
further identification of other phases.
Example

14.  Computer searching of the PDF:
 Computerization has dramatically improved the
efficiency of searching the JCPDS database
 Cards are no longer printed –data are on CD-ROM
 Numerous third-party vendors have software for
searching the PDF database
 Computerized “cards” can contain much more
crystallographic information
Database is still expanding …
 New approach – whole pattern fitting

15. Special
symbol

16. Searching of the PDF requires high-quality data
Accurate line positions are a must!
Calibration of camera and diffractometer with standards
Careful measurement of line intensities
Elimination of artifacts (e.g. preferred orientation)
Solid solutions and strains shift peak positions
“Garbage in, garbage out”
Errors in database

17. EVA software
TOPAS software