Unrestricted Document Shay,
As someone working for one of the vendors, I agree with most of the advice already given. Most importantly, send samples or at least request data from a NIST certified standard that is roughly similar to what you will be studying. It is the only way to truly evaluate instrument performance. As much as we try to thoroughly understand diffraction physics, sometimes we are surprised by the interaction of a specific sample with our instrumentation. This also helps you avoid getting tricked by the numbers game- it doesn't really matter if a detector has 197 vs 255 channels, a 145 mm vs 150 mm radius, 2.17 deg/sec or 2.5 deg/sec slew rate, or any of the other silly numbers that get promoted as the "differentiating" factor. Any individual number is meaningless if not taken into consideration with the entirety of the instrument design (for example, a bigger detector isn't necessarily faster if the goniometer radius is also bigger). I recommend that you specify your requested scan parameters as range, total time, and minimum number of data points in the top half of the peak (for example, 5 to 90 deg 2theta in 10 minutes with at least 7 data points above the half maximum) and look at the data in total counts rather than count rate. Different vendors use different definitions for counting time which can confuse the calculation of count rate. Also, optimal step size varies with pixel size, goniometer radius, and subsampling rate so you will not get identical step sizes from the different instruments. If anybody is interested: for linear position sensitive detectors, I have seen counting time defined as the time one data point is observed by one channel or as the time one data point is observed by all channels of the detector. Both definitions are correct as long as they are clearly defined, but I do have a strong preference for the latter since it inherently normalizes for detectors that have a different number of channels. Also, be clear if you need an instrument that is optimized for a particular material class or if you need a versatile instrument for a wide range of materials. Vendors can configure an instrument that performs very well for something like low angle clay analysis, but it might compromise other measurements. And, of course, a generalized instrument may not give the best possible low angle data. I do have a couple personal opinions to share, but please keep in mind that I am not totally impartial. I think the decision between theta-theta or omega-2theta goniometer can be important. I have a strong preference for theta-theta goniometers after having run a university lab where poorly prepared samples spilled out of the sample holders on omega-2theta goniometers. Finally, do not believe any vendor's marketing material (ours included) that claims that specimen fluorescence can be totally solved by energy discriminating detectors. The detector can filter out fluoresced noise, but it cannot regain the signal that was lost by absorption of the X-rays and cannot correct for the loss of penetration depth that may compromise your particle statistics. Energy discrimination is useful to filter out noise from the occasional fluorescent material, but if you are mostly working with Fe-bearing materials then you should get a Co tube or other non-Cu anode. Cu anodes are the most common, but they are not the "industry standard" as some people think. Again, I will be upfront that I work for one of the vendors. But this advice is mostly based as someone who bought instruments from three different vendors when I managed a university lab. Regards, Scott Speakman Principal Scientist- XRD Malvern Panalytical Unrestricted Document From: rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> On Behalf Of Bish, David L Sent: Wednesday, June 14, 2023 6:50 AM To: Shay Tirosh <stiro...@gmail.com>; iangie <ian...@126.com> Cc: rietveld_l@ill.fr Subject: Re: [External] Re:recommended questions to XRD supplier. Some people who received this message don't often get email from b...@indiana.edu<mailto:b...@indiana.edu>. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. Hi Shay, I echo some of the other comments. A few other things: Learn how alignment will be performed (e.g., is it a black-box arrangement?) and how well you can produce close to 0.000 zero error. Is an independent water chiller required? How expensive and available are replacement X-ray tubes? It is also important that you obtain data for samples representative of the things you anticipate examining. For example, if you will run many Fe-bearing samples, make sure to include one in your test suite (to evaluate fluorescence). I suggest that you obtain data for materials with low-angle peaks, to evaluate the performance. Many of the newer instruments have poor (my assessment) performance at low angles, below perhaps 12 degrees 2-theta in many cases, and analysis of things like clay minerals is significantly impacted. I assume any manufacturer will provide data for the NIST LaB6, to allow you to assess instrument resolution and profile shapes. You might consider obtaining data on a very small sample, e.g., a few mg or smaller, and data obtained very quickly, e.g., < 1 minute for a reasonable scan range. For all of these, make sure you receive the full run conditions, e.g., slit sizes, run parameters (time, step size), tube power, etc. All of these should give you a good picture of instrument performance. Regarding sample changers, I believe some other manufacturers supply these with their benchtop instruments. Personally, I find these useful primarily in a production mode rather than for research. I have one and I seldom use it. An advantage of some is that they add the ability to spin samples. Best of luck with your search, it's always exciting to be able to purchase a new instrument. Rather than focus your search on a single instrument, it might be better in many ways to look at several different instruments/companies. Doing so often yields improved responsiveness and even price. If a company knows that you have decided on their instrument, most incentive is lost. I have not used the Panalytical benchtop instrument, but I have had good experiences with several others. Regards, David Bish ________________________________ From: rietveld_l-requ...@ill.fr<mailto:rietveld_l-requ...@ill.fr> <rietveld_l-requ...@ill.fr<mailto:rietveld_l-requ...@ill.fr>> on behalf of iangie <ian...@126.com<mailto:ian...@126.com>> Sent: Wednesday, June 14, 2023 5:07 AM To: Shay Tirosh <stiro...@gmail.com<mailto:stiro...@gmail.com>> Cc: rietveld_l@ill.fr<mailto:rietveld_l@ill.fr> <rietveld_l@ill.fr<mailto:rietveld_l@ill.fr>> Subject: [External] Re:recommended questions to XRD supplier. This message was sent from a non-IU address. Please exercise caution when clicking links or opening attachments from external sources. Hi Shay, Every company will answer that their product is the best. I suggest you send typical samples you are going to run in the future, to each potential company and compare the demo data quality. In your contract state that "demo data need be resonably reproducible before acceptance", so the company won't dare to cheet with high configure data. This is how I buy machines. -- Dr. Xiaodong (Tony) Wang At 2023-06-14 14:50:26, "Shay Tirosh" <stiro...@gmail.com<mailto:stiro...@gmail.com>> wrote: Dear Rietvelds, We are currently exploring the possibility of acquiring a new benchtop XRD instrument, specifically the Benchtop XRD from Malvern-Pananalytical. We have scheduled a Zoom meeting with the supplier to discuss this further. Before the meeting takes place, I would like to prepare by gathering relevant information. Could you please provide some recommended questions that we can ask the supplier? We aim to gain a comprehensive understanding of the instrument and compare its performance to other options available. Feel free to suggest and comment. Thank you for your assistance. Best regards, Shay -- Dr. Shay Tirosh Materials Scientist. With focusing on Photovoltaics, Electrochemistry, Thin film coatings, and nanotechnology. 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