Author Topic: Standard/ unknown different coating?  (Read 5938 times)

UofO EPMA Lab

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Re: Standard/ unknown different coating?
« Reply #15 on: August 14, 2019, 12:46:14 pm »
While at M&M last week I was asked a question about analyzing standards in Probe for EPMA. That is one acquires data on a standard and then from the Analyze! window one clicks the Analyze button to get a quantitative analysis of that standard *as though it were an unknown*.

Of course if the standard is the primary (assigned) standard for that element, the element in question will iterate to the correct concentration, because the standard is analyzing itself as the standard. That is why the %VAR (percent variance) value for that element is displayed in parentheses- because it isn't really a test of the analytical quality. 

Of course it should be pointed out that even though Probe for EPMA only utilizes the intensities of the elements actually assigned as the primary standard for that element, if one is analyzing a standard sample as an unknown in the Analyze! window, the matrix corrections will not be able to exactly converge correctly on the (ideal or published) concentration of the assigned element for this primary standard, if there is something significantly wrong with the other (unassigned) elements in that standard sample.

So in the case of our Fe (pure metal) standard shown in the previous post, because we have analyzed carbon on a carbon coated standard, of course we detect a significant amount (~10 wt%) of carbon as being in the Fe metal standard. Now the matrix iteration correctly calculates the std k-factor for our pure metal standard (the one we are analyzing as an unknown!) as being 1.0, but when it calculates the matrix correction physics for our Fe standard as containing ~10 wt% carbon, of course it cannot converge to the 100% Fe as one might expect:

St  526 Set   3 Iron metal, Results in Elemental Weight Percents
 
ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn
BGDS:      EXP     EXP     LIN     EXP     LIN     LIN     EXP     EXP     LIN     LIN     LIN
TIME:    40.00   40.00   40.00   40.00   20.00   20.00   20.00   40.00   20.00   20.00   20.00
BEAM:    49.56   49.56   49.56   49.56   49.56   49.56   49.56   49.56   49.56   49.56   49.56

ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn   SUM 
   156   -.160  10.904   -.002    .011   -.006    .002   -.016    .357 102.982    .011    .008 114.091
   157   -.085  10.732   -.020    .007   -.019   -.013   -.003    .372 101.793   -.003   -.007 112.755
   158   -.285  10.792   -.025    .006    .011   -.002    .033    .432 102.560   -.019   -.009 113.495

AVER:    -.177  10.809   -.016    .008   -.004   -.004    .005    .387 102.445   -.003   -.003 113.447
SDEV:     .101    .087    .012    .002    .015    .007    .025    .040    .603    .015    .009    .669
SERR:     .058    .050    .007    .001    .008    .004    .015    .023    .348    .009    .005
%RSD:   -57.10     .81  -78.83   30.67 -328.34 -169.36  544.36   10.29     .59 -433.32 -346.16

PUBL:     n.a.    n.a.    n.a.    n.a.    n.a.    n.a.    n.a.    n.a. 100.000    n.a.    n.a. 100.000
%VAR:      ---     ---     ---     ---     ---     ---     ---     ---  (2.45)     ---     ---
DIFF:      ---     ---     ---     ---     ---     ---     ---     ---  (2.45)     ---     ---
STDS:      604     506     542     514     528     523     529     913     526     524     525


And again, this doesn't matter for any other sample that uses this Fe standard, because only the measured Fe intensities (from the standard sample), and the (ideal) composition from the standard database is being utilized for the std k-factor calculation, but if one really wants to see the composition of any carbon coated standards analyzed as though they were actual unknowns, one can simply select all the standards (except of course the carbon standard!), then click the Elements/Cations button and then click the carbon row and check the "Disable Quant" checkbox and click OK and OK. Then we will get output like this when analyzing our carbon coated standards as unknowns:

St  526 Set   3 Iron metal, Results in Elemental Weight Percents
 
ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn
BGDS:      EXP     EXP     LIN     EXP     LIN     LIN     EXP     EXP     LIN     LIN     LIN
TIME:    40.00     ---   40.00   40.00   20.00   20.00   20.00   40.00   20.00   20.00   20.00
BEAM:    49.56     ---   49.56   49.56   49.56   49.56   49.56   49.56   49.56   49.56   49.56

ELEM:        N     C-D      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn   SUM 
   156   -.124     ---   -.002    .011   -.006    .002   -.016    .299 100.558    .011    .008 100.741
   157   -.066     ---   -.020    .007   -.018   -.012   -.003    .311  99.405   -.003   -.007  99.595
   158   -.221     ---   -.025    .007    .011   -.002    .032    .362 100.161   -.018   -.009 100.297

AVER:    -.137     ---   -.016    .008   -.004   -.004    .005    .324 100.041   -.003   -.003 100.211
SDEV:     .078     ---    .012    .002    .014    .007    .025    .033    .586    .014    .009    .578
SERR:     .045     ---    .007    .001    .008    .004    .014    .019    .338    .008    .005
%RSD:   -57.14     ---  -78.83   30.68 -328.37 -169.35  544.25   10.33     .59 -433.25 -346.11

PUBL:     n.a.    n.a.    n.a.    n.a.    n.a.    n.a.    n.a.    n.a. 100.000    n.a.    n.a. 100.000
%VAR:      ---     ---     ---     ---     ---     ---     ---     ---   (.04)     ---     ---
DIFF:      ---     ---     ---     ---     ---     ---     ---     ---   (.04)     ---     ---
STDS:      604     ---     542     514     528     523     529     913     526     524     525
« Last Edit: August 14, 2019, 12:47:48 pm by UofO EPMA Lab »
UofO MicroAnalytical Facility

Philipp Poeml

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Re: Standard/ unknown different coating?
« Reply #16 on: September 18, 2019, 02:46:39 am »

When we do this, we can analyze a uncoated sample using a standard that is carbon coated and the differences in the coating are compensated for in the matrix correction:

Un    6 H13 trav
TakeOff = 40.0  KiloVolt = 15.0  Beam Current = 50.0  Beam Size =    0
(Magnification (analytical) =  40000),        Beam Mode = Analog  Spot
(Magnification (default) =      400, Magnification (imaging) =   1572)
Image Shift (X,Y):                                         .00,    .00
Number of Data Lines:   5             Number of 'Good' Data Lines:   1
First/Last Date-Time: 08/13/2019 04:01:21 PM to 08/13/2019 04:27:59 PM
WARNING- Using Exponential Off-Peak correction for n ka
WARNING- Using Exponential Off-Peak correction for c ka
WARNING- Using Exponential Off-Peak correction for si ka
WARNING- Using Exponential Off-Peak correction for cu ka
WARNING- Using Exponential Off-Peak correction for o ka
WARNING- Using Time Dependent Intensity (TDI) Element Correction

Average Total Oxygen:         .000     Average Total Weight%:  100.766
Average Calculated Oxygen:    .000     Average Atomic Number:   24.805
Average Excess Oxygen:        .000     Average Atomic Weight:   46.435
Average ZAF Iteration:        4.00     Average Quant Iterate:     3.00

No Sample Coating and/or No Sample Coating Correction

Un    6 H13 trav, Results in Elemental Weight Percents
 
ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn
BGDS:      EXP     EXP     LIN     EXP     LIN     LIN     EXP     EXP     LIN     LIN     LIN
TIME:    60.00   60.00   60.00   60.00   36.00   40.00   36.00   90.00   20.00   40.00   40.00
BEAM:    48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49

ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn   SUM 
   165   3.406   2.406   1.224    .872    .194    .953    .092    .284  86.449   4.550    .334 100.766

AVER:    3.406   2.406   1.224    .872    .194    .953    .092    .284  86.449   4.550    .334 100.766
SDEV:     .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000
SERR:     .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000
%RSD:      .00     .00     .00     .00     .00     .00     .00     .00     .00     .00     .00
STDS:      604     506     542     514     528     523     529     913     526     524     525

STKF:    .1637   .9635   .9910  1.0000  1.0000  1.0000   .9974   .2509  1.0000   .9988  1.0000
STCT:    29.07  853.49  258.45 1148.84  609.87  416.77  562.01  195.43  210.20  154.13  188.74

UNKF:    .0142   .0061   .0103   .0061   .0018   .0107   .0008   .0015   .8480   .0573   .0032
UNCT:     3.02    5.58    2.72    7.15    1.14    4.53     .48    1.28  181.90    9.01     .62
UNBG:     1.25     .74     .32     .28    2.39     .68    2.82    2.54     .64     .29     .39

ZCOR:   2.4014  3.9407  1.1922  1.4274  1.0606   .8939  1.1019  1.8968  1.0194   .7941  1.0359
KRAW:    .1040   .0065   .0105   .0062   .0019   .0109   .0009   .0066   .8654   .0585   .0033
PKBG:     3.41    8.50    9.52   26.38    1.48    7.63    1.17    1.51  283.94   32.20    2.60
INT%:     ----    ----    ----    ----    ----    ----    ----    ----     .00    ----   -1.01

TDI%:     .000   3.192   -.735    .000    .851    .000    .000  -4.725   2.630    .000    .000
DEV%:       .0     4.6     6.6      .0     4.9      .0      .0     3.8      .4      .0      .0
TDIF:     ---- LOG-LIN LOG-LIN    ---- LOG-LIN    ----    ---- LOG-LIN LOG-LIN    ----    ----
TDIT:      .00  111.00  112.00     .00  103.00     .00     .00  151.00   74.00     .00     .00
TDII:     ----    6.32    3.03    ----    3.55    ----    ----    3.69    183.    ----    ----
TDIL:     ----    1.84    1.11    ----    1.27    ----    ----    1.31    5.21    ----    ----


And what happens if you switch on the C coating correction here? Does it change something significantly?

Probeman

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Re: Standard/ unknown different coating?
« Reply #17 on: September 18, 2019, 09:02:16 am »
Hi Philipp,
Well of course if the sample was actually carbon coated, the measured carbon concentration would be much higher since we would be measuring that additional carbon, but if you're asking if the physics calculations would be different, the answer is yes.

The presence of a coating does two things. It first reduces the effective landing energy of the incident electrons, which mostly affects the calculation for low overvoltage elements such as Fe. And second it decreases the transmission of x-rays out of the sample, mostly low energy emission lines such as oxygen for example. But this latter effect can be offset by the increase in ionization efficiency due to less overvoltage for these low energy edges.

The only way to know is to do the physics calculation. The coating correction calculation in PFE is rather simple, and includes a calculation for electron energy loss from the coating material and thickness, and a calculation for x-ray absorption for the emitted x-rays.  The code is on GitHub.

For the previous example I had to relocate the specific file and found that I had re-standardized since the post you quoted, so the uncoated calculation numbers are slightly different. So I will show both the uncoated and coated calculations here, first the calculation assuming the standards are coated and the sample is uncoated (the actual situation):

Un    6 H13 trav
TakeOff = 40.0  KiloVolt = 15.0  Beam Current = 50.0  Beam Size =    0
(Magnification (analytical) =  40000),        Beam Mode = Analog  Spot
(Magnification (default) =      400, Magnification (imaging) =   1572)
Image Shift (X,Y):                                         .00,    .00
Number of Data Lines:   5             Number of 'Good' Data Lines:   1
First/Last Date-Time: 08/13/2019 04:01:21 PM to 08/13/2019 04:27:59 PM
WARNING- Using Exponential Off-Peak correction for n ka
WARNING- Using Exponential Off-Peak correction for c ka
WARNING- Using Exponential Off-Peak correction for si ka
WARNING- Using Exponential Off-Peak correction for cu ka
WARNING- Using Exponential Off-Peak correction for o ka
WARNING- Using Time Dependent Intensity (TDI) Element Correction

Average Total Oxygen:         .000     Average Total Weight%:  100.818
Average Calculated Oxygen:    .000     Average Atomic Number:   24.804
Average Excess Oxygen:        .000     Average Atomic Weight:   46.430
Average ZAF Iteration:        4.00     Average Quant Iterate:     3.00

No Sample Coating and/or No Sample Coating Correction

Un    6 H13 trav, Results in Elemental Weight Percents
 
ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn
BGDS:      EXP     EXP     LIN     EXP     LIN     LIN     EXP     EXP     LIN     LIN     LIN
TIME:    60.00   60.00   60.00   60.00   36.00   40.00   36.00   90.00   20.00   40.00   40.00
BEAM:    48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49

ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn   SUM 
   165   3.412   2.401   1.244    .901    .197    .965    .093    .284  86.432   4.555    .335 100.818

AVER:    3.412   2.401   1.244    .901    .197    .965    .093    .284  86.432   4.555    .335 100.818
SDEV:     .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000
SERR:     .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000
%RSD:      .00     .00     .00     .00     .00     .00     .00     .00     .00     .00     .00
STDS:      604     506     542     514     528     523     529     913     526     524     525

STKF:    .1637   .9635   .9910  1.0000  1.0000  1.0000   .9974   .2509  1.0000   .9988  1.0000
STCT:    29.03  855.51  254.38 1112.32  602.82  412.03  558.75  195.85  210.25  154.02  188.04

UNKF:    .0142   .0061   .0104   .0063   .0019   .0108   .0008   .0015   .8478   .0573   .0032
UNCT:     3.02    5.58    2.72    7.15    1.14    4.53     .48    1.28  181.90    9.01     .62
UNBG:     1.25     .74     .32     .28    2.39     .68    2.82    2.54     .64     .29     .39

ZCOR:   2.4026  3.9431  1.1922  1.4271  1.0606   .8942  1.1019  1.8988  1.0195   .7944  1.0360
KRAW:    .1041   .0065   .0107   .0064   .0019   .0110   .0009   .0066   .8652   .0585   .0033
PKBG:     3.41    8.50    9.52   26.38    1.48    7.63    1.17    1.51  283.94   32.20    2.60
INT%:     ----    ----    ----    ----    ----    ----    ----    ----     .00    ----   -1.01

TDI%:     .000   3.192   -.735    .000    .851    .000    .000  -4.725   2.630    .000    .000
DEV%:       .0     4.6     6.6      .0     4.9      .0      .0     3.8      .4      .0      .0
TDIF:     ---- LOG-LIN LOG-LIN    ---- LOG-LIN    ----    ---- LOG-LIN LOG-LIN    ----    ----
TDIT:      .00  111.00  112.00     .00  103.00     .00     .00  151.00   74.00     .00     .00
TDII:     ----    6.32    3.03    ----    3.55    ----    ----    3.69    183.    ----    ----
TDIL:     ----    1.84    1.11    ----    1.27    ----    ----    1.31    5.21    ----    ----

And here the same calculation assuming that both the standards and samples are coated (and as stated above, the sample was actually not coated, so this is a physically unreal situation):

Un    6 H13 trav
TakeOff = 40.0  KiloVolt = 15.0  Beam Current = 50.0  Beam Size =    0
(Magnification (analytical) =  40000),        Beam Mode = Analog  Spot
(Magnification (default) =      400, Magnification (imaging) =   1572)
Image Shift (X,Y):                                         .00,    .00
Number of Data Lines:   5             Number of 'Good' Data Lines:   1
First/Last Date-Time: 08/13/2019 04:01:21 PM to 08/13/2019 04:27:59 PM
WARNING- Using Exponential Off-Peak correction for n ka
WARNING- Using Exponential Off-Peak correction for c ka
WARNING- Using Exponential Off-Peak correction for si ka
WARNING- Using Exponential Off-Peak correction for cu ka
WARNING- Using Exponential Off-Peak correction for o ka
WARNING- Using Time Dependent Intensity (TDI) Element Correction

Average Total Oxygen:         .000     Average Total Weight%:  103.635
Average Calculated Oxygen:    .000     Average Atomic Number:   24.695
Average Excess Oxygen:        .000     Average Atomic Weight:   45.780
Average ZAF Iteration:        4.00     Average Quant Iterate:     3.00

Using Conductive Coating Correction For Electron Absorption and X-Ray Transmission:
Sample Coating=C, Density=2.1 gm/cm3, Thickness=200 angstroms, Sin(Thickness)=311.145 angstroms

Un    6 H13 trav, Results in Elemental Weight Percents
 
ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn
BGDS:      EXP     EXP     LIN     EXP     LIN     LIN     EXP     EXP     LIN     LIN     LIN
TIME:    60.00   60.00   60.00   60.00   36.00   40.00   36.00   90.00   20.00   40.00   40.00
BEAM:    48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49   48.49

ELEM:        N       C      Mo      Si      Ni       V      Cu       O      Fe      Cr      Mn   SUM 
   165   4.082   2.468   1.265    .917    .201    .984    .095    .317  88.315   4.648    .342 103.635

AVER:    4.082   2.468   1.265    .917    .201    .984    .095    .317  88.315   4.648    .342 103.635
SDEV:     .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000
SERR:     .000    .000    .000    .000    .000    .000    .000    .000    .000    .000    .000
%RSD:      .00     .00     .00     .00     .00     .00     .00     .00     .00     .00     .00
STDS:      604     506     542     514     528     523     529     913     526     524     525

STKF:    .1637   .9635   .9910  1.0000  1.0000  1.0000   .9974   .2509  1.0000   .9988  1.0000
STCT:    29.03  855.51  254.38 1112.32  602.82  412.03  558.75  195.85  210.25  154.02  188.04

UNKF:    .0170   .0063   .0106   .0064   .0019   .0110   .0009   .0016   .8652   .0584   .0033
UNCT:     3.02    5.58    2.72    7.15    1.14    4.53     .48    1.28  181.90    9.01     .62
UNBG:     1.25     .74     .32     .28    2.39     .68    2.82    2.54     .64     .29     .39

ZCOR:   2.3957  3.9291  1.1921  1.4258  1.0617   .8953  1.1032  1.9250  1.0208   .7955  1.0373
KRAW:    .1041   .0065   .0107   .0064   .0019   .0110   .0009   .0066   .8652   .0585   .0033
PKBG:     3.41    8.50    9.52   26.38    1.48    7.63    1.17    1.51  283.94   32.20    2.60
INT%:     ----    ----    ----    ----    ----    ----    ----    ----     .00    ----   -1.03

TDI%:     .000   3.192   -.735    .000    .851    .000    .000  -4.725   2.630    .000    .000
DEV%:       .0     4.6     6.6      .0     4.9      .0      .0     3.8      .4      .0      .0
TDIF:     ---- LOG-LIN LOG-LIN    ---- LOG-LIN    ----    ---- LOG-LIN LOG-LIN    ----    ----
TDIT:      .00  111.00  112.00     .00  103.00     .00     .00  151.00   74.00     .00     .00
TDII:     ----    6.32    3.03    ----    3.55    ----    ----    3.69    183.    ----    ----
TDIL:     ----    1.84    1.11    ----    1.27    ----    ----    1.31    5.21    ----    ----


As we can see, the assumption of a coated sample, when it was not actually coated, provides a poor result.
« Last Edit: September 18, 2019, 10:25:54 am by Probeman »
The only stupid question is the one not asked!

Philipp Poeml

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Re: Standard/ unknown different coating?
« Reply #18 on: September 20, 2019, 02:27:16 pm »
Hi John,

Thanks for replying! I think what I meant was:
You Write

No Sample Coating and/or No Sample Coating Correction


So, does it mean all coating correction is off?
Why not switch it on and define the standards as carbon coated and the unknown not?

John Donovan

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Re: Standard/ unknown different coating?
« Reply #19 on: September 20, 2019, 02:55:02 pm »
Hi John,

Thanks for replying! I think what I meant was:
You Write

No Sample Coating and/or No Sample Coating Correction


So, does it mean all coating correction is off?
Why not switch it on and define the standards as carbon coated and the unknown not?

No, it just means that the (global) coating corrections were turned on in the Analytical | Analysis Options dialog, but that no sample coating was specified for this particular sample.

I think if you read this topic from the beginning it explains all this. For example, see here:

https://probesoftware.com/smf/index.php?topic=23.msg1402#msg1402
« Last Edit: September 20, 2019, 03:02:15 pm by John Donovan »
John J. Donovan, Pres. 
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Philipp Poeml

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Re: Standard/ unknown different coating?
« Reply #20 on: September 20, 2019, 03:07:54 pm »
I see. Then I got it wrong. So coating correction was on for standards, but the sample was specified as uncoated. That makes total sense. Sorry for the confusion.

John Donovan

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Re: Standard/ unknown different coating?
« Reply #21 on: September 20, 2019, 03:17:28 pm »
I see. Then I got it wrong. So coating correction was on for standards, but the sample was specified as uncoated. That makes total sense. Sorry for the confusion.

No worries, it's good to ask questions! 

Yes.  The global coating corrections (for standards and unknowns) in the Analytical | Analysis Options dialog were both turned on (energy loss and x-ray absorption from the coating), the standard sample coatings were specified in the Standard | Edit Standard Coating Parameters menu (the standard coatings are usually specified by default in the Probewin.ini file, but they are ignored if the Analysis Options parameters are not checked), and the unknown sample did not have a coating specified in the Analyze! Calculation Options dialog.

The reason the coating parameters are specified in different places for standards and unknowns is that the standards coating parameters are global, and the unknown coating parameters are specified on a sample by sample basis.
« Last Edit: September 20, 2019, 10:12:15 pm by John Donovan »
John J. Donovan, Pres. 
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"Not Absolutely Certain, Yet Reliable"