Re: NIST SRM656 Analysis

Dear Matthew, I scanned our SRM α 656 using CoKα Dynamic Beam Optimation machine from 2 to 150 °2θ. https://www.dropbox.com/s/rar6sjepl9g2x2d/ROW.pro?dl=0 Using the same sample model, the derived relative wt% ratio between α and β phases are very similar to that from your CuKα data.

Re:RE: NIST SRM656 Analysis

al std. Also, the external method should give better results when you have a mixture of well-known references in several proportions, a kind of calibration curve. This is what Matt is going through, although this approach is time-consuming. From:rietveld_l-requ...@ill.fr On Behalf Of Matthe

RE: NIST SRM656 Analysis

Kletti mailto:holger.kle...@uni-weimar.de>> Cc: RIETVELD_L Distribution List mailto:rietveld_l@ill.fr>> Subject: Re: NIST SRM656 Analysis Hi Holger There is a good paper by Ian Madsen, Nikki Scarlett, and Arnt Kern about the quantification of amorphous materials - https://doi.o

Re: Re: NIST SRM656 Analysis

Hi Tony I can't reproduce the certificate values. This is the entire point of my question. Matthew On Fri, 29 Apr 2022, 08:31 iangie, wrote: > Dear Mathew, > > Understood these values are from the SRM certificate. > My .pro of the data suggests ~92% alpha, 3% beta, and ~5% Amorphous: >

Re: NIST SRM656 Analysis

Yep. The sample is supposed to contain 87.4 wt% alpha-Si3N4, 3.0 wt% beta-Si3N4 and 9.6 wt% amorphous. Matthew On Tue, 26 Apr 2022 at 20:06, Martin Vickers wrote: > Just a point of interest you seem to have a few impurity peaks > possibly from Si6N8 (COD entry 96-210-2554 seems to match

Re: NIST SRM656 Analysis

Hi Ed The beam is smaller than the sample over all angles. - 0.25° divergence at 250 mm radius. I also collected in constant divergence mode, so the diffracting volume is a constant. Matthew On Fri, 15 Apr 2022 at 01:20, Edward Laitila wrote: > Just curious, is the sample as prepared in the

Re: NIST SRM656 Analysis

*From:* rietveld_l-requ...@ill.fr > *On Behalf Of *Matthew Rowles > *Sent:* torsdag 14. april 2022 09:03 > *To:* Jonathan WRIGHT > *Cc:* RIETVELD_L Distribution List > *Subject:* Re: NIST SRM656 Analysis > > > > Hi Jon > > > > The data is put on an absolut

Re: NIST SRM656 Analysis

Just curious, is the sample as prepared in the holder wider than the beam width at 10 degrees where you start the scan? This is a common issue that not many realize that for quantitative analysis the diffracting volume is constant provided the sample is larger than the beam in the tube and

Re: NIST SRM656 Analysis

* Jonathan WRIGHT *Cc:* RIETVELD_L Distribution List *Subject:* Re: NIST SRM656 Analysis Hi Jon The data is put on an absolute scale through the external standard approach. The calculations assume that the QPA for corundum in NIST SRSM676a is 99.02 wt%. This scaling factor is th

Re: NIST SRM656 Analysis

Hi Jon The data is put on an absolute scale through the external standard approach. The calculations assume that the QPA for corundum in NIST SRSM676a is 99.02 wt%. This scaling factor is then applied to the silicon nitride pattern. re surface roughness: The samples were backpacked against a

Re:Re: NIST SRM656 Analysis

Dear Jon, It might be just me, my current QPA practise is to micronise all samples down to 10-40 micron range and make a flat sample surface for the machine to scan. I trust the SRMs are already fine enough and Matthrew packed them well. There are roughness correction models but they may be

Re: NIST SRM656 Analysis

Maybe a silly question: are you assuming you have the data on an absolute scale in order to do these calculations? Do things like surface roughness somehow not matter? Best Jon On 13/04/2022 11:56, Matthew Rowles wrote: Thanks Tony When I add the absorption edge correction to the

Re: Re: NIST SRM656 Analysis

Thanks Tony When I add the absorption edge correction to the silicon nitride model (and add beta-silicon nitride), it becomes -2.8 wt% amorphous; up a little due to the added correction and down a little due to the extra phase. If I change your al-SN thermals from 1 to those given in ICSD 77811,

Re:Re: NIST SRM656 Analysis

Dear Matthew, I tried your data and get ~-1% amorphous. My .pro is in below link. https://www.dropbox.com/s/xuw13c91l9gq5m5/ROW.pro?dl=0 I normally do not refine Beq, which I believe gives biggest source of error in QPA... Cheers! -- Dr. Xiaodong (Tony) Wang Senior Research

Re: NIST SRM656 Analysis

Thanks Mathew, for the summary of the replies you received off-list. Just a remark to those who reply off-list. The purpose of the Rietveld list is to facilitate discussion. That can't happen if the conversation is off-list. Alan Dr Alan Hewat, NeutronOptics

Re: NIST SRM656 Analysis

Hi all Thanks to those that have replied off-list. I've managed to jiggle things around and get various answers. If you want an answer between -14 and +6 wt% amorphous, I can make it happen. I can either use charged atoms or not, or use thermal parameters or not. Combining those between the

Re: NIST SRM656 Analysis

Hi all I've collected some more data, and am still getting spurious results, and by spurious, I mean -5 wt% amorphous in SRM-alpha-656 when quantified by the external method against SRM 676a. We had some SRM-656alpha (couldn't find any of the beta) stored in a drying oven, and some SRM676a

NIST SRM656 Analysis

Hi List People Do any of you use NIST SRM656 in your quantitative analysis quality control? I've recently started at a new lab, and am finding it impossible to make a physically realistic model (in Topas) that gives results anywhere near correct (or at least, close to the certificate values).