Probe Software Users Forum

General EPMA => Discussion of General EPMA Issues => Topic started by: Dominik on June 30, 2021, 04:52:56 AM

Title: Low totals with EuPd2Si2
Post by: Dominik on June 30, 2021, 04:52:56 AM

Hi,

I am currently analysing some synthetic material: EuPd2Si2. The standards are re-produced well and there is no (significant) chemical peak-shift on the synthetic material compared to the standards (metals and Eu-Phosphate). There are no element interferences (Si: PETL, Pd: PETL, Eu: LiFH).
The totals, however, are hovering around 98±0.5 wt%, and I don't know why. My idea would be the matrix correction. Any idea what else might be the case?

 Thanks,  Dominik

Title: Re: Low totals with EuPd2Si2
Post by: sem-geologist on June 30, 2021, 05:47:36 AM

What is Si standard? Si peak can shift significantly when changing oxidation state sign (+4 -> -4).

Title: Re: Low totals with EuPd2Si2
Post by: JonF on June 30, 2021, 06:19:11 AM

There's some pretty major uncertainty in the MAC for Si Ka in Eu according to the tables in CalcZAF:

Code: [Select]

MAC value for Si ka in Eu =    3524.53  (LINEMU   Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV)
MAC value for Si ka in Eu =    4627.80  (CITZMU   Heinrich (1966) and Henke and Ebisu (1974))
MAC value for Si ka in Eu =    5714.24  (MCMASTER McMaster (LLL, 1969) (modified by Rivers))
MAC value for Si ka in Eu =    4280.05  (MAC30    Heinrich (Fit to Goldstein tables, 1987))
MAC value for Si ka in Eu =    4628.93  (MACJTA   Armstrong (FRAME equations, 1992))
MAC value for Si ka in Eu =    4110.83  (FFAST    Chantler (NIST v 2.1, 2005))

Edit to add, the Pd La in Eu MAC is pretty uncertain, too!

Code: [Select]

MAC value for Pd La in Eu =    1190.30  (LINEMU   Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV)
MAC value for Pd La in Eu =    1503.30  (CITZMU   Heinrich (1966) and Henke and Ebisu (1974))
MAC value for Pd La in Eu =    1687.39  (MCMASTER McMaster (LLL, 1969) (modified by Rivers))
MAC value for Pd La in Eu =    1569.85  (MAC30    Heinrich (Fit to Goldstein tables, 1987))
MAC value for Pd La in Eu =    1503.67  (MACJTA   Armstrong (FRAME equations, 1992))
MAC value for Pd La in Eu =    1395.47  (FFAST    Chantler (NIST v 2.1, 2005))


Title: Re: Low totals with EuPd2Si2
Post by: Probeman on June 30, 2021, 09:07:27 AM

I think Jon is correct that this could be very similar to the Mg ka in Fe situation where one sees high totals in garnet using the JEOL software which uses the Cal Tech MAC value:

MAC value for Mg Ka in Fe =    5239.40  (LINEMU   Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV)
MAC value for Mg Ka in Fe =    6120.70  (CITZMU   Heinrich (1966) and Henke and Ebisu (1974))
MAC value for Mg Ka in Fe =    5395.10  (MCMASTER McMaster (LLL, 1969) (modified by Rivers))
MAC value for Mg Ka in Fe =    5518.65  (MAC30    Heinrich (Fit to Goldstein tables, 1987))
MAC value for Mg Ka in Fe =    6089.53  (MACJTA   Armstrong (FRAME equations, 1992))
MAC value for Mg Ka in Fe =    5089.56  (FFAST    Chantler (NIST v 2.1, 2005))

That is to say, MACs in the 10^3 range often result in differences of one or two percent absolute.

Title: Re: Low totals with EuPd2Si2
Post by: Dominik on June 30, 2021, 10:47:53 AM

Thanks! I'm using a JEOL, maybe that is the reason.

And regarding standard: I am using a metal and tested whether there is a peak-shift. That is not significant and I corrected for that.

Title: Re: Low totals with EuPd2Si2
Post by: JonF on June 30, 2021, 10:56:24 AM

Quote from: Dominik on June 30, 2021, 10:47:53 AM

Thanks! I'm using a JEOL, maybe that is the reason.

You could type in the raw results from the JEOL (in cps/nA) for both the standards and unknowns in to CalcZAF (having added the standards to the standard.mdb file), then have a play around with both the MAC tables and the PRZ correction and see if it gives you the right results.

Title: Re: Low totals with EuPd2Si2
Post by: Probeman on June 30, 2021, 12:06:47 PM

Quote from: JonF on June 30, 2021, 10:56:24 AM

Quote from: Dominik on June 30, 2021, 10:47:53 AM

Thanks! I'm using a JEOL, maybe that is the reason.

You could type in the raw results from the JEOL (in cps/nA) for both the standards and unknowns in to CalcZAF (having added the standards to the standard.mdb file), then have a play around with both the MAC tables and the PRZ correction and see if it gives you the right results.

Just because the JEOL has a high MAC for Mg ka in Fe, doesn't mean that the MAC for Si Ka in Eu is low. But it might be!  The only way to know for sure is to perform multi-voltage intensity measurements on a Europium silicide (ideally) and use an application such as XMAC to iteratively solve for the MAC value:

https://probesoftware.com/smf/index.php?topic=1340.msg9638#msg9638

You could also perform multi-voltage measurements on your unknown, but you'll need to enter the approximate composition of the unknown into XMAC so it can partition the MACs.

In any event, I agree with Jon. Once you have your raw data in CalcZAF you can also utilize the "Use All Matrix Corrections" option and also select different MAC tables.

Title: Re: Low totals with EuPd2Si2
Post by: Dominik on June 30, 2021, 12:56:26 PM

I will now go and familiarise myself with CalcZAF ... (first trying to install it on my Mac with some Windows virtualisation).
Thanks for the hint.

Title: Re: Low totals with EuPd2Si2
Post by: Probeman on July 01, 2021, 07:44:06 AM

Quote from: Dominik on June 30, 2021, 12:56:26 PM

I will now go and familiarise myself with CalcZAF ... (first trying to install it on my Mac with some Windows virtualisation).
Thanks for the hint.

Here's a link to a topic you might find helpful for running CalcZAF on a Mac:

https://probesoftware.com/smf/index.php?topic=284.0