Standards for meteorite samples

[EPMA_Gremlin]

Hi;
we are analysing some meteorite samples and have encountered a nickel phosphide (Fe,Ni)3P mineral want to use Fe3P as a standard.  Can anyone help with getting a single crystal of this material, synthetic for preference.  I have tried all the usual crystal growers and have not identified any.  We did at one stage try and purchase a Fe3P MAC standard but this is no longer available?

My first post to this forum

Cheers
Colin

[sem-geologist]

Hi;
we are analysing some meteorite samples and have encountered a nickel phosphide (Fe,Ni)3P mineral want to use Fe3P as a standard.  Can anyone help with getting a single crystal of this material, synthetic for preference.  I have tried all the usual crystal growers and have not identified any.  We did at one stage try and purchase a Fe3P MAC standard but this is no longer available?

Why not use highly available GaP as standard for P?

[Mike Jercinovic]

Hi Colin,
Up until the day he passed, Joe Goldstein used a natural Schreibersite included in a nickel iron meteorite as a P standard for meteoritic phosphides.  He maintained that the P was stoichiometric in Schreibersite, so just knowledge of the Fe,Ni ratio was the only thing that needed to be determined (not a very big effect anyway).  I don't know which meteorite he used, but it was (and still is) in his own mount along with Fe, Ni, and Co pure metals.  As PKa originates from a transition involving the valence band, the peak position changes substantially compared to phosphates.  Probably a peak shape effect too, so using an actual (FeNi)phosphide is undoubtedly a little better than just using a phosphate standard and then updating the peak position on the unknown phosphide.  I know the community is throwing a lot of shade on these sorts of 'internal' laboratory standards, but one might say that Joe did okay.

Mike J.

[Probeman]

Up until the day he passed, Joe Goldstein used a natural Schreibersite included in a nickel iron meteorite as a P standard for meteoritic phosphides.  He maintained that the P was stoichiometric in Schreibersite, so just knowledge of the Fe,Ni ratio was the only thing that needed to be determined (not a very big effect anyway).  I don't know which meteorite he used, but it was (and still is) in his own mount along with Fe, Ni, and Co pure metals.  As PKa originates from a transition involving the valence band, the peak position changes substantially compared to phosphates.  Probably a peak shape effect too, so using an actual (FeNi)phosphide is undoubtedly a little better than just using a phosphate standard and then updating the peak position on the unknown phosphide.  I know the community is throwing a lot of shade on these sorts of 'internal' laboratory standards, but one might say that Joe did okay.

You just identified one of the many problem with using "internal standards".    They are difficult if not impossible to reproduce!   How is Colin to obtain Joe's standard? 

I'm sure that Joe did a great job using this standard and I might even accept his assurance that the P is stoichiometric, but then there's the issue you mentioned with the Fe/Ni ratio, so yet another problem!

I think Colin is exactly correct to seek a high purity synthetic that matches the valence of his sample.  Come on people, let's go global and source these high purity synthetics...

Well deserved shade perhaps!   

[Probeman]

Hi;
we are analysing some meteorite samples and have encountered a nickel phosphide (Fe,Ni)3P mineral want to use Fe3P as a standard.  Can anyone help with getting a single crystal of this material, synthetic for preference.  I have tried all the usual crystal growers and have not identified any.  We did at one stage try and purchase a Fe3P MAC standard but this is no longer available?

Why not use highly available GaP as standard for P?

I agree that GaP is worth a try. But also worth checking the differences in the absorption correction relative to Fe3P.

[Probeman]

Up until the day he passed, Joe Goldstein used a natural Schreibersite included in a nickel iron meteorite as a P standard for meteoritic phosphides.  He maintained that the P was stoichiometric in Schreibersite, so just knowledge of the Fe,Ni ratio was the only thing that needed to be determined (not a very big effect anyway).  I don't know which meteorite he used, but it was (and still is) in his own mount along with Fe, Ni, and Co pure metals.  As PKa originates from a transition involving the valence band, the peak position changes substantially compared to phosphates.  Probably a peak shape effect too, so using an actual (FeNi)phosphide is undoubtedly a little better than just using a phosphate standard and then updating the peak position on the unknown phosphide.  I know the community is throwing a lot of shade on these sorts of 'internal' laboratory standards, but one might say that Joe did okay.

We've know for over 300 years why "internal standards" are not our best course of action:

“by Standards kept by each particular workman, without any agreement or reference to one another”
-Edmond Halley, 1693

[Probeman]

we are analysing some meteorite samples and have encountered a nickel phosphide (Fe,Ni)3P mineral want to use Fe3P as a standard.  Can anyone help with getting a single crystal of this material, synthetic for preference.  I have tried all the usual crystal growers and have not identified any.  We did at one stage try and purchase a Fe3P MAC standard but this is no longer available?

I note this PhD thesis published in 2010 by John William Howard, University of Nevada Las Vegas on testing of Fe3P, on page 35:

"The samples used were obtained from Alpha Aesar chemical supply company; samples of single crystal F e3P were selected and examined prior to experimental runs to test for crystal integrity..."

I also note a group at Ames growing synthetic sulfide and phosphide single crystals published in 2023:

https://www.mdpi.com/2075-163X/13/3/429

Might be worth contacting...

[crystalgrower]

GaP is NOT a phosphate.  Neither is InP (found in many Canadian-made 44 metal mounts).   User manuals and websites clearly state these are PHOSPHIDES.

There is absolutely no reason to be concerned about any peak shift since there is NO oxygen in these 99.9999+% pure semiconductors. 

Fe in Fe3P would be calibrated using pure Fe, and to calibrate the P you need something with more P than the sample.   

[Probeman]

GaP is NOT a phosphate.

No one in this thread suggested that it was.