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*

This is an interesting system, with significant absorption of Al Ka by Ni and the existence of characteristic fluorescence of Ni Ka by Pt La.  The system also exhibits significant continuum fluorescence of both Ni Ka and Pt La.  Here is output from the GMR thin film program for NiPt as a bulk sample:
 
 GMR Electron Probe Bulk Microanalysis        File:FI070404.L06     4-Apr- 7
 ===========================================================================
 
 Analysis # 1 at 20kV;   Pouchou,Pichoir's Scanning (1990) Model;   iter.= 0
 Continuum Correction Included
 
 Elements :  Ni;Ka , Pt;La1                                                  
 
 
          Composition        K-ratio        Fchar    Fcont
        Weight%  Atom%   Cmp.Std. Pure El.    %        %
        =======  =====   =======  =======   ======   =====
 Ni :    23.13   50.00   -------  0.30315     4.04    5.58
 Pt :    76.87   50.00   -------  0.69171     0.00   -1.39
 sum:   100.00
 
There is continuum fluorescence observed for the pure element standards and for the sample, with higher cf in the sample.  Result is overestimation of Ni and Pt, with greater overestimation of Ni relative to Pt.  There is an excellent example of this system as a ~1um Pt film on Ni substrate which is presented in Pouchou and Pichoir's paper on the PAP correction in the green book.  At voltages low enough to generate x-rays only in the overlying Pt film, there is significant excitation of Ni in the substrate due entirely to continuum fluorescence.  It is an excellent demonstration of the need to address that effect -- we use it as a prime example in the Lehigh Advanced Quant course.
 
For research grade analysis in this Al-Ni-Pt system it would really be necessary to have a Ni-Al and Ni-Pt set of standards to handle the absorption and fluorescence issues.  Multiple KV analysis should be used.
 
Cheers,
 
Paul
 
Paul Carpenter
Washington University
Campus Box 1169
1 Brookings Drive
Saint Louis, MO 63130-4862
 


From: JEOL-Focused Probe Users List [mailto:[log in to unmask]] On Behalf Of John J. Donovan
Sent: Wednesday, April 04, 2007 11:42 AM
To: [log in to unmask]
Subject: Re: [PROBE-USERS] Ni-Pt-Al standard?

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Moderator: Ellery Frahm, [log in to unmask], Electron Microprobe Lab, University of Minnesota

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* Hi Ellery,
Some calculations are below for both Pt La and Pt Ma. There is a significant absorption correction for Al so lower voltages will help somewhat there (so long as you can still excite Ni Ka!). Ni is slightly fluoresced, obviously by Pt. I'm just guessing on your composition, but clearly smaller amounts of Al will experience a larger absorption correction.

Pt La
 ELEMENT K-VALUE ELEMWT% OXIDWT% ATOMIC% KILOVOL
   Ni ka  .35142  33.000   -----  28.762    15.0
   Pt la  .23560  33.000   -----   8.656    15.0
   Al ka  .22780  33.000   -----  62.583    15.0
   TOTAL:         99.000   ----- 100.000

 ELEMENT  ABSCOR  FLUCOR  ZEDCOR  ZAFCOR STP-POW BKS-COR  F(CHI)
   Ni ka  1.0141   .9836   .9415   .9390   .9344  1.0076   .9745
   Pt la   .9957  1.0000  1.4067  1.4007  1.4784   .9515   .9794
   Al ka  1.6431   .9989   .8826  1.4486   .7720  1.1432   .5400

Pt Ma
 ELEMENT K-VALUE ELEMWT% OXIDWT% ATOMIC% KILOVOL
   Ni ka  .35142  33.000   -----  28.762    15.0
   Pt ma  .25120  33.000   -----   8.656    15.0
   Al ka  .22780  33.000   -----  62.583    15.0
   TOTAL:         99.000   ----- 100.000

 ELEMENT  ABSCOR  FLUCOR  ZEDCOR  ZAFCOR STP-POW BKS-COR  F(CHI)
   Ni ka  1.0141   .9836   .9415   .9390   .9344  1.0076   .9745
   Pt ma  1.1085  1.0000  1.1851  1.3137  1.5208   .7792   .6286
   Al ka  1.6431   .9989   .8826  1.4486   .7720  1.1432   .5400


There is also of course the 5th order overlap of Ni Ka V on Al Ka to worry about...
For Al ka      TAP at  8.35835 angstroms, concentration of   33.000 wt.%
  Interference by Ni KA1      V     at  8.29130 =      9.2%
  Interference by Ni KA2      V     at  8.30970 =      6.2%

So long as your metals are freshly polished, pure metals should be fine. At least accuracy of your standards won't be in question!

Note that because the relatively large Al absorption this system is of some interest, a number of AlNi single crystals were grown to study this. I got mine from GE (Eric Lifshin). This would be an excellent secondary standard if you can get it.
john

At 09:00 AM 4/4/2007, Ellery Frahm wrote:

I have a post-doc researcher here in one of our engineering departments who is interested in analyzing a Ni-Pt-Al system.  I've been trying pure metals as standards for his samples, but obviously I'd like to minimize any absorption or fluorescence issues there might be.  Does anyone have any experience with such a system?  Do you know of suitable standards for such a system, or have you just used pure metals?

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