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Quantitative Analysis
Nickel-based superalloy
The nickel-based superalloy
analyzed here contains Al, Ti, Cr, Co, Ta, W, Re and Mo in addition to Ni.
While the W, Ta, and Re
contribute to the ED spectrum, identification by ED is complicated by the
presence of the large Ni Kβ line at 8.264 keV, along with several other
L-family lines associated with Ta, W, and Re in the spectrum. The WD
spectrum (Fig. 8), shows the lines from W, Ta, and Re, all clearly
separated.
Quantitative results taken on
this specimen are listed in Table 3. The alloy has first been analyzed using
only EDS. Note that the standard deviations for Ta, W and Re are relatively
high because of poor statistics and severe peak overlaps.
| |
ED only |
ED and WD |
| |
analysed wt% |
std. dev. wt% |
analysed wt% |
std dev wt% |
method |
| Al |
4.87 |
0.09 |
4.83 |
0.09 |
ED |
| Ti |
1.007 |
0.05 |
1.011 |
0.05 |
ED |
| Cr |
6.4649 |
0.09 |
6.406 |
0.09 |
ED |
| Co |
9.62 |
0.151 |
9.55 |
0.153 |
ED |
| Ni |
59.377 |
0.35 |
58.86 |
0.35 |
ED |
| Mo |
0.629 |
0.11 |
0.533 |
0.01 |
WD |
| Ta |
7.03 |
0.48 |
7.136 |
0.078 |
WD |
| W |
6.393 |
0.55 |
6.585 |
0.077 |
WD |
| Re |
3.264 |
0.443 |
3.099 |
0.05 |
WD |
Table 3: Quantitative analysis of nickel-based superalloy comparing ED only
with ED and WD analyses.
The second set of results is a
combination of ED and WD data. Using INCAEnergy+, WD data is acquired
simultaneously with the ED spectrum. Hence the total analysis time may not
need to be increased. For trace elements and peaks that are severely
overlapped in the ED spectrum, a large improvement in statistical precision
can be obtained by using WD.
In general, statistical errors in
the WD results can be much less than for ED quantitative analysis. This is
because higher currents can be used, the peaks are not overlapped and have a
better peak to background ratio.
Combined ED/WD analysis is a very
practical way of achieving reliable quantitative analysis. ED can be used
for accurate quantification of the elements present in relatively large
amounts, and WD can be used for accurate quantification of elements present
in amounts below 1 wt%. By using both techniques, the analyst exploits the
speed of EDS analysis and the sensitivity of the WDS technique.
BPSG film
Borophosphosilicate (BPSG) films
are used as a passivation layer for silicon devices in the semiconductor
industry and the concentrations of boron and phosphorus affect the
properties of these films.
Quantitative analysis of boron is
virtually impossible using ED analysis because of the relatively poor peak
to background ratio of the boron peak. However, using modern LSM crystals
(in this case the LSM-200) it is possible to achieve excellent count rates
with relatively low electron beam currents. Quantitative results are shown
in table 4.
| |
wt% |
sigma
wt% |
at % |
| B |
2.35 |
0.04 |
4.22 |
| P |
3.77 |
0.06 |
2.36 |
| Si |
37.6 |
0.38 |
25.98 |
| O |
54.6 |
0.36 |
66.23 |
| N |
0.87 |
0/19 |
1.21 |
Table4: Quantitative analysis of a BPSG film using WDS
Counting precision, even for a
very light element such as boron, is excellent and the WD technique is a
viable method for analysis of BPSG films.
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