Author Topic: Standard/ unknown different coating?  (Read 6348 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 »
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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 »
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Probeman

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Re: Standard/ unknown different coating?
« Reply #22 on: January 21, 2020, 04:46:01 pm »
We recently were running some magnetite analyses for a customer and after standardizing we analyzed a few unknown grains and found surprisingly low totals, even after we specified calculating excess oxygen by applying the method of Droop (1987) as described in this post:

https://probesoftware.com/smf/index.php?topic=92.msg8593#msg8593

Un   41 Chill-9 Mgt-Ilm 1_MGT Replace, Results in Elemental Weight Percents
 
ELEM:       Fe      Mg      Ti       V      Mn      Cr      Al      Si      Ca       O
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    CALC
BGDS:      MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN
TIME:    50.00  120.00   80.00   60.00   60.00   60.00   60.00   60.00   40.00     ---
BEAM:    50.35   50.35   50.35   50.35   50.35   50.35   50.35   50.35   50.35     ---

ELEM:       Fe      Mg      Ti       V      Mn      Cr      Al      Si      Ca       O   SUM 
   469  53.826   1.046   9.557    .275    .423   -.002   1.061    .038    .013  26.413  92.650
   470  53.689   1.039   9.748    .265    .419    .001   1.057    .039    .012  26.434  92.702
   471  53.788   1.046   9.764    .274    .419    .003   1.067    .043    .021  26.500  92.925
   472  53.684   1.040   9.588    .260    .423   -.007   1.064    .051    .044  26.390  92.535
   473  53.646   1.042   9.752    .264    .427   -.003   1.079    .044    .057  26.462  92.770
   474  53.809   1.048   9.729    .267    .432   -.008   1.047    .036    .055  26.500  92.913
   475  53.318   1.058   9.764    .272    .424   -.013   1.027    .092    .066  26.375  92.385
   476  53.640   1.056  10.168    .270    .433   -.005    .989    .026    .037  26.600  93.214
   477  53.530   1.076  10.094    .270    .428   -.005    .987    .029    .035  26.541  92.986
   478  53.220   1.084  10.430    .262    .437    .003    .962    .036    .045  26.583  93.061
   479  52.999   1.083  10.291    .243    .438    .000    .952    .041    .024  26.421  92.492

AVER:   53.559   1.056   9.899    .266    .428   -.003   1.026    .043    .037  26.474  92.785
SDEV:     .268    .017    .295    .009    .007    .005    .046    .018    .018    .077    .259
SERR:     .081    .005    .089    .003    .002    .001    .014    .005    .005    .023
%RSD:      .50    1.61    2.98    3.43    1.58 -154.27    4.47   40.66   48.92     .29
STDS:      395      12      22      23      25      24     306      14     306     ---

So of course we first tried to analyzed some standards as unknowns and they came out just fine. Well it turned out that this user had carbon coated their thin sections themselves and because they weren't quite sure of the procedure they apparently laid on a *very* thick coat of carbon. After we removed the thin section from the probe it did indeed appear to be quite dark, so we walked over to the stylus profilometer and measured the carbon coat, after scratching some areas clean with a razor blade. And lo and behold, indeed we had close to 70 nm of carbon on these thin sections!   :o

So we went back to the probe and turned on the coating correction in the Analysis Options menu by checking the two boxes as described here:

https://probesoftware.com/smf/index.php?topic=23.msg1402#msg1402

and then we specified this extra thick carbon coat in the Calculation Options as shown here:



and now we analyze the sample again and now it's much better:

Un   41 Chill-9 Mgt-Ilm 1_MGT Replace, Results in Elemental Weight Percents
 
ELEM:       Fe      Mg      Ti       V      Mn      Cr      Al      Si      Ca       O
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    CALC
BGDS:      MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN
TIME:    50.00  120.00   80.00   60.00   60.00   60.00   60.00   60.00   40.00     ---
BEAM:    50.35   50.35   50.35   50.35   50.35   50.35   50.35   50.35   50.35     ---

ELEM:       Fe      Mg      Ti       V      Mn      Cr      Al      Si      Ca       O   SUM 
   469  57.884   1.137  10.181    .287    .453   -.003   1.142    .040    .014  28.369  99.504
   470  57.736   1.129  10.384    .276    .449    .001   1.137    .042    .013  28.391  99.556
   471  57.842   1.137  10.401    .286    .449    .003   1.148    .046    .022  28.462  99.796
   472  57.731   1.130  10.214    .270    .453   -.008   1.144    .054    .047  28.343  99.379
   473  57.690   1.133  10.389    .275    .458   -.004   1.161    .047    .061  28.420  99.629
   474  57.865   1.139  10.364    .278    .463   -.009   1.126    .039    .058  28.461  99.784
   475  57.338   1.150  10.402    .283    .455   -.014   1.105    .098    .070  28.327  99.214
   476  57.683   1.148  10.832    .281    .464   -.005   1.064    .028    .039  28.567 100.101
   477  57.565   1.169  10.753    .281    .459   -.006   1.062    .031    .037  28.504  99.857
   478  57.232   1.178  11.111    .273    .468    .003   1.035    .038    .048  28.547  99.933
   479  56.994   1.177  10.963    .252    .470    .000   1.024    .044    .026  28.374  99.324

AVER:   57.596   1.148  10.545    .277    .458   -.004   1.104    .046    .040  28.433  99.643
SDEV:     .289    .018    .314    .010    .007    .005    .049    .019    .019    .082    .277
SERR:     .087    .006    .095    .003    .002    .002    .015    .006    .006    .025
%RSD:      .50    1.61    2.98    3.54    1.58 -143.60    4.47   40.64   48.93     .29
STDS:      395      12      22      23      25      24     306      14     306     ---

Note that the reason for Fe being so affected by this extra thick carbon coat is not due to x-ray absorption. The major effect is from electron energy loss from this extra thick carbon coat and hence a significantly lower landing energy for the incident electrons. This lowers the overvoltage (at 15 keV) significantly enough to cause the previously observed low totals.

Just for fun, here is the excess oxygen calculation along with the oxide and cation output:

Ferrous/Ferric Calculation Results:
        Ferric/TotalFe   FeO        Fe2O3    Oxygen from Fe2O3 
   469        .350      48.405      28.964       2.902
   470        .344      48.734      28.388       2.844
   471        .343      48.877      28.381       2.843
   472        .349      48.386      28.767       2.882
   473        .343      48.764      28.288       2.834
   474        .347      48.585      28.737       2.879
   475        .342      48.516      28.060       2.811
   476        .338      49.150      27.850       2.790
   477        .340      48.911      27.946       2.800
   478        .330      49.348      26.984       2.704
   479        .333      48.892      27.151       2.720

AVER:         .342      48.779      28.138       2.819

Un   41 Chill-9 Mgt-Ilm 1_MGT Replace, Results in Oxide Weight Percents

ELEM:      FeO     MgO    TiO2    V2O3     MnO   Cr2O3   Al2O3    SiO2     CaO       O   SUM 
   469  74.467   1.885  16.982    .423    .585   -.004   2.157    .087    .020   2.902  99.504
   470  74.278   1.872  17.322    .406    .579    .001   2.148    .089    .018   2.844  99.556
   471  74.414   1.886  17.350    .420    .580    .004   2.169    .099    .031   2.843  99.796
   472  74.271   1.874  17.038    .398    .585   -.012   2.162    .116    .065   2.882  99.379
   473  74.218   1.878  17.329    .405    .591   -.005   2.193    .101    .085   2.834  99.629
   474  74.443   1.889  17.288    .409    .597   -.013   2.127    .083    .082   2.879  99.784
   475  73.765   1.907  17.351    .417    .587   -.020   2.087    .210    .099   2.811  99.214
   476  74.210   1.903  18.068    .414    .600   -.008   2.009    .060    .055   2.790 100.101
   477  74.057   1.939  17.937    .414    .592   -.008   2.007    .067    .052   2.800  99.857
   478  73.629   1.953  18.534    .401    .604    .005   1.955    .081    .067   2.704  99.933
   479  73.322   1.951  18.288    .370    .607    .000   1.934    .095    .036   2.720  99.324

AVER:   74.097   1.903  17.590    .407    .592   -.005   2.086    .099    .055   2.819  99.643
SDEV:     .371    .031    .524    .014    .009    .008    .093    .040    .027    .063    .277
SERR:     .112    .009    .158    .004    .003    .002    .028    .012    .008    .019
%RSD:      .50    1.61    2.98    3.54    1.58 -143.60    4.47   40.64   48.93    2.25
STDS:      395      12      22      23      25      24     306      14     306     ---

Un   41 Chill-9 Mgt-Ilm 1_MGT Replace, Results Based on Sum of 3 Cations

ELEM:       Fe      Mg      Ti       V      Mn      Cr      Al      Si      Ca       O   SUM 
   469   2.297    .104    .471    .013    .018    .000    .094    .003    .001   3.929   6.929
   470   2.290    .103    .480    .012    .018    .000    .093    .003    .001   3.930   6.930
   471   2.288    .103    .480    .012    .018    .000    .094    .004    .001   3.929   6.929
   472   2.293    .103    .473    .012    .018    .000    .094    .004    .003   3.930   6.930
   473   2.285    .103    .480    .012    .018    .000    .095    .004    .003   3.929   6.929
   474   2.290    .104    .478    .012    .019    .000    .092    .003    .003   3.931   6.931
   475   2.280    .105    .482    .012    .018   -.001    .091    .008    .004   3.932   6.932
   476   2.276    .104    .498    .012    .019    .000    .087    .002    .002   3.934   6.934
   477   2.276    .106    .496    .012    .018    .000    .087    .002    .002   3.934   6.934
   478   2.261    .107    .512    .012    .019    .000    .085    .003    .003   3.936   6.936
   479   2.265    .107    .508    .011    .019    .000    .084    .003    .001   3.937   6.937

AVER:    2.282    .104    .487    .012    .018    .000    .091    .004    .002   3.932   6.932
SDEV:     .011    .002    .014    .000    .000    .000    .004    .001    .001    .003    .003
SERR:     .003    .001    .004    .000    .000    .000    .001    .000    .000    .001
%RSD:      .50    1.59    2.88    3.47    1.53 -143.63    4.54   40.88   48.99     .07
« Last Edit: January 22, 2020, 08:49:15 am by Probeman »
The only stupid question is the one not asked!