AN ANALYTICAL XRAY SERVICES LABORATORY
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I spend a great deal of time meeting with XRD and XRF users throughout the year, but usually in the context of some problem or time-sensitive project. Luckily I’ve been able to attend the Denver X-ray Conference fairly consistently over the last few years. It’s a great time to catch up with other users who are as deeply invested in X-ray spectroscopy and crystallographic analysis as we are. The vendors always put on a great show in the exhibit hall and poster sessions.

The first three days of the week are filled with technical workshops focused on an array of topics. There are always some introductory classes for both XRD and XRF for new users to attend and then there will be additional topics which are usually more advanced. The educational opportunities alone are well worth the attendance fee. Each session is run by an expert in the field and questions, even from industrial users, are welcomed. The sessions are strictly non-sales oriented as well which lends the event a very egalitarian feeling. See the full program here.

Plenary sessions and more sales-oriented meetings occur later in the week and are a great way to get a feel for the cutting edge technology being released by the various vendors. The exhibit hall opens a few days into the conference so everyone has a few days to see all the different booths. We always spend a great deal of time at the Materials Data, Inc and Bruker-AXS booths in particular.

The conference moves between Westminster, CO just North of Denver, Chicago, IL and Big Sky, MO. I’ve never made the trek up to Big Sky, but I hear it’s beautiful. Some attendees only come when it’s up there.

I’d love to connect with as many of our readers as possible so contact us if you’ll be there and I’ll be sure to see you while I’m at DXC-Big Sky!

A great many factors affect the quality of data one can collect on any given instrument, but there are times when simply holding the aliquot is a major hurdle. We spend a great deal of time working out the best ways to hold odd samples and even create custom hardware to do so in some cases. Click here for some of our other posts related to the various sample holders we work with. Choosing the best sample holder for a given project is one thing, but there are also times when a completely different stage is required.

The most common stage is the simple, single sample stage. This relies on three pins to define the plane of diffraction. The sample holder is pressed against these pins by a spring loaded plunger beneath it.

The dreaded “amorphous” hump created by x-rays scattering off plastic sample holders has plagued XRD users for decades. It’s a serious enough problem that we make a good volume of these holders from Aluminum which works very well for loose powders. The plastic scatters xrays at around 13 degrees 2Theta (Cu anode tube) which make a real mess of most geological patterns and isn’t fun to model out for Rietveld refinement. Zero background holders like our ZBH-32 work wonderfully in standard sample stages designed for a single sample at a time, but the large plate isn’t compatible with the autosampler.

I recently had a request for a hybrid holder which would allow for analysis of very small volumes of materials while retaining compatibility with the autosampler. This is almost identical to our standard powder holders, but with a well designed specifically for our small ZBH plate.

Key features include:

  • 6061-T6 Al material (anodized or as-machined)
  • Si(510) plate
  • Raised sample well minimizes the area of the sample holder in the plane of diffraction. (Original Siemens design)
  • Beveled well walls minimize the area of Al in the plane of diffraction
  • Other small modifications are made to improve reliability of these holders in the autosampler

One of the fundamental facts of lab-based X-ray production is that our x-ray tubes emit much more than the pure KA1 lines we rely on for material characterization and quantification. Most XRD users are familiar with techniques and hardware for the reduction or elimination of KB1, W LA1 and Bremsstrahlung, but take for granted the inseparable pair of KA1 and KA2 (referred to as the “doublet”). Luckily for us, these energies are present in strict proportion such that we can factor their paired presence into most XRD analysis to the point that one might barely notice their effect. However, the fact remains that we will see peak broadening at lower angles and completely independent additional peaks at higher angles due to this superfluous discrete emission.

Separating the doublet cannot be accomplished electronically or through absorption/attenuation such as might be effective for KB1 energies. It must be done in the primary-beam with an additional diffraction event. Primary-beam monochromators are generally classified by the number of diffraction events required for a photon to pass completely through the device. Single-bounce, 2-bounce and 4-bounce geometries are common with the latter providing the best energy resolution allbeit the lowest intensity (photon flux). My limited experience suggests that while the single-bounce models retain enough intensity to have some application in powder XRD, the others are relegated to HR-XRD applications such as XRR.

The alignment for any of this hardware is not for the faint of heart as it begins with coarse adjustments using fluorescent screens in the beam path. This was essential for us given how dramatically misaligned the monochromator had become after so many attempts to bring it back into operation. We actually needed our SDD system to verify that we were tuning for Cu KA1 energy rather than the KB1 emissions because some of the most basic aspects of the alignment had pushed way beyond their intended position.

Along the way we built ourselves a motorized remote adjustment tool which we’ll return to the user as small adjustments are required on a regular basis with this kind of monochromator to retain maximum intensity. It’s quite useful and even versatile enough to allow for the adjustment of multiple control knobs.

One final note regarding intensity. It’s easy to get excited about energy resolution like this, but bear in mind that we’re looking at ~20x reduction in intensity due to the inherent losses involved in the primary diffraction event. This data was collected at 10x the normal speed and at half the normal 2Theta step increment so it looks very good, but one would need a compelling reason to slow their data collection this much.

Another side effect of performing your energy discrimination in the primary beampath is that other issues such as fluorescence effects (incident x-rays exciting elements in the sample causing high background intensities) are harder to avoid than they would be with a diffracted-beam monochromator. The 4x reduction in intensity inherent in the diffracted-beam monochromatization makes it a poor choice to eliminate these effects when the incident intensities are already so low. We recommend energy-dispersive detectors such as our SDD-150 to eliminate extraneous energies without sacrificing net intensity. We’ve also worked with the Bruker LynxEye XE-T detector which has a very high energy resolution compared to other position sensitive detectors (PSD). Contact KS Analytical Systems for more information on these options.

FCT 0027 Xray decal visual croppedWe’ve been working with XRD machines for about 40 years now and to be quite honest, very little has changed. Most of the really exciting advancements have been software based, but there have certainly been changes to the hardware as well. We’ve introduced a few ourselves such as the KSA-SDD-150 detector. Automatic anti-scatter and divergence slits, additional axes and degrees of control have all increase the versatility of these instruments and opened them up to more advanced and unique experiments, but nothing has had an effect matching the new crop of Position Sensitive Detector (PSD). These have been around for decades, but didn’t really become popular until the a solid state version was introduced. There are still some trade-offs as mentioned in our KSA-SDD-150 post, but when you need speed, a PSD is the way to go.

Until recently, the only option for clients looking for this kind of speed was either a new XRD or a refurbished Bruker D8 system with a LynxEye or Vantec-1. While the D8 is a great machine and the LynxEye is a world class detector, the cost is usually too much for academic or small labs to bear. This has all been changing recently with the introduction of a truly aftermarket detector system from FCT ACTech. No other company that we’re aware of has worked so hard to make their hardware as turnkey as possible so the user isn’t left holding a box of parts and an instruction manual.

We can now offer detector upgrades for D5000 Theta/Theta and D5000 T2T systems with kits soon to be available for D500 systems as well. Software integration with DiffracPlus (standard software for Bruker XRD systems) is seamless and full integration with MDI Datascan is very close to completion. The future is very bright for users of these XRD systems.

Contact us for more information on these detectors


NovaculitesiliconKey features:

  • Data collection at 30x the speed of a standard point detector.
  • Dramatic increase in throughput
  • Plug-and-play retrofit
  • Maintenance free (no gas charge required)
  • Stand-alone operation for custom experiments
  • Excellent angular resolution

 

Technical Specifications:

  • Maximum count rate: 500Kcps / pixcel, 50Mcps global
  • Maximum scanning speed: 120 deg/min
  • Angular resolution: 0.06 deg at 200mm radius
  • Strip pitch: 120um
  • Number of channels: 96
  • Angular span: 3.3 degrees
  • Energy resolution: <10%
  • Energy range: 4.5KeV to 17KeV, efficiency at 30KeV is 10%
  • Compatible with all common XRD tube anodes including Cr, Fe, Co, Cu, Mo and W.

20141124_161938Our recent sealed sample cell project required a thin covering film to be applied over loose powder before analysis by XRD. We tested a few options for this film as part of the design process and the results were interesting enough that we thought it would be worth dedicating a full post to that data and expanding the range of materials a bit to satisfy our curiosity.

All data was collected on our primary powder system. This is a Siemens D5000 configured with a theta/theta goniometer, automatic anti-scatter and divergence slits, a standard sealed Cu tube (LFF) and our new KSA-XRD-150 detector system. We alternate between a digital phi stage, 40-position autosampler and the standard, single sample stage which was used in these experiments. I had a spare sealed-sample cell available which made it easy to exchange the films without disturbing the sample surface. The design of these stretches the film taught each time the cell is assembled. I’d originally tried to simply lay the film over a side-load holder, but without being tightly held, it would buckle enough that results at low angles were probably affected. A NiO standard powder was used due to its high purity and compositional difference from any of the film materials.

The data clearly shows that Polyimide was the best choice for this application as it resulted in very limited attenuation as well as an extremely minimal increase in background intensity/amorphous scatter. Some of the other patterns were very interesting though.

20141124_161656 NiO CONTROL No film

 

 

 

 

 

 

 

 

 

NiO Prolene copy NiO Mylar copy

 

 

 

 

 

 

 

 

 

NiO Polycarbonate copy NiO Polyimide copy

 

 

 

 

 

 

 

 

 

 

NiO Polypropylene copy

 

 

NiO Prolene

Scotch “Magic” office tape. Adhesive side down.

NiO Scotch packing

Scotch “Heavy duty” packing tape. Adhesive side down.

 

 

 

 

 

 

 

 

 

 

Energy-dispersive detectors have been in use on XRD systems for decades, but have always come with caveats. Low energy resolution, Liquid nitrogen cooling, slow start-up and tedious/cryptic tuning controls have limited their popularity in many applications. Silicon Drift technology solves most of these issues and modern electronics covers the rest. The new KSA-SDD system for X-ray diffraction utilizes a full spectrum EDXRF detector which is fully software tuned. The result is a detection system with high enough energy resolution to match the performance of the traditional diffracted-beam monochromator/scintillation counter combination without the inherent 75% intensity drop. The increased countrate allows for much faster data collection speeds with the same counting statistics. We’ve been using this technology at our in-house testing lab (Texray Laboratory Services) for several months to great effect while we refined the system and are now ready to open it up to all XRD users. Contact us to discuss options for integration into your diffractometer.

SDD-XRD-150 installed on a Siemends D5000TT PXRD system. This is one of the powder systems we operate at Texray-Lab.

SDD-XRD-150 installed on a Siemends D5000TT PXRD system. This is one of the powder systems we operate at Texray-Lab.

The detector mounts directly in place of the original scintillation counter.

The detector mounts directly in place of the original scintillation counter.

 

 

 

 

 

 

 

 

 

 

 

Speed

  • Scanning 3-4 times as fast as the traditional scintillation counter/diffracted beam monochromator yields nearly identical results.
  • Scanning at the same rate results in much smoother scans, greatly improved statistical data and lower limits of detection/quantification.
Novaculite SDD vs SC

Complete scan of Novaculite Quartz with a diffracted beam monochromator and scintillation counter vs the new KSA-SDD-150.

Novaculite SDD vs SC 5 fingers

5-fingers of Quartz scan of Novaculite Quartz with a diffracted beam monochromator and scintillation counter vs the new KSA-SDD-150.

 

 

 

 

 

 

 

 

 

Energy resolution

  • 140eV under ideal conditions.
  • All KB peaks eliminated electronically.
  • W LA1 (8.40 KeV) lines eliminated from Cu KA1,2 (8.04 KeV) scans even with thoroughly contaminated tubes.
  • Common fluorescence energies (i.e. Fe when Cu tube anodes are used) are greatly reduced. (Bremsstrahlung effects are impossible to remove completely)
  • Most PSD detectors offer no better than 650eV. This allows for a great deal of fluorescence energy to pass as well as W LA1 from older Cu tubes.

Low angle scatter

  • The detector mounts in place of the traditional scintillation counter allowing for use of automated variable (motorized) or interchangeable aperture slits to control angular resolution. Scans starting from 0.5 degrees 2? are possible with the proper slit arrangement just as they are with the scintillation counter. The user controls the intensity vs angular resolution of the scan based upon the ideal conditions for their work rather than the limitations of the hardware.
  • Position sensitive detectors are wide open by design which necessitates knife edges over the sample and additional mechanical aperture plates to block air scatter at low angles. Closing off the detector limits the useable channels and reduces the benefit of these detectors dramatically.
Novaculite SDD vs SC low angle

Minimal low angle scatter due to the use of standard aperture slits.

Novaculite SDD vs SC Cu KB1 and W LA1

Cu KB1 and W LA1 energies diffract from the 100% peak of Novaculite in between the two primary peaks shown here. Tests with a severely contaminated tube showed no W LA1 passing through the discriminator.

 

 

 

 

 

 

 

 

 

Truly zero maintenance design

  • No delays – The detector is ready to collect data almost as soon as power is applied.
  • No external cooling – Air backed Peltier cooling eliminates the need for water circulation and/or liquid nitrogen.
  • Zero maintenance vacuum design eliminates reliance on an ion pump/backup battery.
  • 12 month warranty against hardware failure under normal use.

Versatility

  • The Digital Pulse Processor (DPP) includes a usb interface allowing for adjustment and refinement should they be necessary for a particular application. With optional software, full quantitative EDXRF analysis can be performed.
  • Compatibility with grazing-incidence attachments and parallel beam optics for analysis of thin films.

 

The detector can be set for any common XRD anode (energy) easily. Multiple energies may even be configured to allow for use with various anodes without the need for additional hardware. We specialize in Siemens (now Bruker) XRD and WD-XRF instrumention and have installation kits ready for the D500, D5000 and D5005. The output is a standard BNC cable with a 5V square pulse output which is standard across every manufacturer we’ve worked with. Kevex and Thermo Si(Li) detectors used this same output.

Please contact KS Analytical Systems for a quote.

 

Some months ago we had a pair of scientists visit our space to look over a refurbished Siemens D5000. Interestingly enough, they’d planned to use the system for some basic XRD, but mainly for the development of polycapillary optics. This is a fascinating new technology that’s gaining steam out in the R&D centers around the world and merits a full post dedicated to it ASAP. This is the type of “game changing” innovation which hasn’t come along in XRD in decades. They took delivery of their machine a few weeks ago, but while on-site they asked about another project. All that’s really needed is simple phase analysis by XRD with one complication, the material reacts violently when exposed to air.

We roughed out a basic design the same day, but that was only the beginning. Dealing with materials like this necessitates careful consideration of all material and procedures involved in getting it from the lab where it’s synthesized to ours and back. The final design involved billet Aluminum, BUNA rubber o-rings and polyimide (Kapton) film and took quite a while to flesh out. The end result is a complete system which allows the customer to load the samples into individual cells inside their own glove box. The individual cells can be loaded into the case inside the glove box as well. The outer o-rings on the cells seal against chamfered edges on the pockets of the case creating a second sealed area above and below the sample. It’s unlikely that the inner cell would ever rupture, but this protects the polyimide film and adds a substantial extra level of safety.

DSC_0348

This is the complete case as it will ship. The flat-head bolts hold everything together and provide the necessary force to seal the chambers.

DSC_0336

With the case open, you can see the individual cells along with the top and bottom of the case. The labeling shouldn’t be necessary since there are strict protocols in place for transportation of this material, but it never hurts to be cautious.

DSC_0331

The original design called for a slightly more secure seal, but when we started working up the procedure to assemble them, it became clear that something simpler was needed, particularly considering that these will be loaded in a glove-box. An 11th hour rehash necessitated new o-rings, modification of the outer cell rings and complete redesign and fabrication of the cell center sections. I think this was well worth the effort though as they’re much easier to assemble now. There’s even a nice little tool to make it easier to open them back up for disposal or reloading. The original design would have been essential disposable.

DSC_0331 (2)

 

 

 

 

 

 

 

 

A large part of our business at KS Analytical Systems is refurbishing and reselling WDXRF and XRD instrumentation. We specialize in Siemens and Bruker models because, and I can’t stress this enough, they last. Siemens was 20 years ahead of their time with features like full computer automation, interlocked radiation housings (not just an enclosed beam path) and independent axis control coming standard on most systems. The D500 may well be the most reliable powder diffractometer ever built and for most of our history, it’s outsold all other models of XRD and XRF combined. Most users are simply performing basic powder scans with many running the optional 40-position sample changer, but I always get excited when I find someone pushing the limits of the platform.

Several years ago I was approached by a new professor at a major American university about purchasing a refurbished Siemens D500 XRD. He’d been seriously considering a new instrument from one of the big-three OEMs, but chose to focus on the D500 due to its reputation for low cost of ownership, versatility and nearly identical resolution/intensity to the new system he’d been looking at. It’s been a few years since that unit was delivered and I’ve been very impressed with the improvements that have been made.

The first step was to bring the software up to date with a complete package from Materials Data Inc. (MDI). This included Datascan 5.0 for instrument control and data acquisition as well as the flagship Jade 9.5 analysis package. Whole pattern fitting (Rietveld), semi-automatic phase ID (Search/Match) and a host of other advanced quantitative and modeling options are included. Jade 9.5 is modular and can be purchased with any combination of these options. I’d estimate that 70% of the XRD systems we sell go out with some level of MDI package. We’ve been working with them for 20 years now and have never heard anything other than glowing praise for their excellent products and support. One key feature of Jade is that it was designed to be a universal analysis solution from the ground up so there’s never a problem opening any of the OEM file formats. It’s much easier to justify the cost to upgrade your software when you know it will integrate seamlessly with any other data or instruments you may encounter. Contact KSA if you’d like more information on this.

Jade 9.5

This is Jade 9.5. You’ll notice that it’s a much different interface than the Jade 2010 program I usually use. This option is modular with available plug-ins for all the higher level functions of Jade 2010, but 9.5 is perpetually licensed.

Virtual XRD

This is actually the VirtualXRD program that comes along with Datascan. I don’t use it often, but some of my users run extremely long count times and predicting the affect of a parameter change could save them days of experimentation. It’s a great tool even for users running simple 1 hour scans.

 

 

 

 

 

 

 

 

 

 

 

The next step was more hardware based than anything else. The independent axis control of the D500 (in Theta/Theta or Theta/2Theta configurations) allows for both rocking curves and grazing incidence scans. With the goal of analyzing thin-films in mind, we upgraded the D500 with a grazing incidence attachment. These are designed to minimize scatter while the sample is held at a shallow (usually 3 degrees) incident angle and the scan is performed with the detector alone. The attachment consists of a long collimator coupled with a simple monochromator just before the detector. We’ve performed some rather intense studies with one of these at Texray and were very impressed with its performance. In fact, we use it whenever practical even though we have a dedicated parallel beam optics system in the lab as well. It was about time for a new tube so a new, ceramic Cu long, fine focus tube was included in the upgrade.

Ceramic XRD tubeGrazing incidence attachment

 

 

 

 

 

 

 

 

 

 

Some additional software solutions were developed on-site to facilitate XRR (X-ray Reflectivity) measurements around the same time. I confess that this is not something I’m personally very familiar with, but it seems fascinating. It involves scans at extremely low angles which can require caution since one is working with a very nearly direct beam.

The last upgrade he made is actually the one that most impressed me and the one I had absolutely nothing to do with. In an effort to further expand the capabilities of his instrument, he purchased and installed an energy dispersive detector with an integral digital pulse processor (DPP). Clever mounting and some experimentation allowed him to perform EDXRF elemental (qualitative AND quantitative) analysis on samples while using the D500s X-ray tube as the primary emission source. The flexibility of the D500 platform even allowed him to control the effective layer depth by adjusting the incident beam angle. Since his application involved analysis of a thin film coating, he set the goniometer to a low angle to minimize penetration depth and substrate interference. After seeing how well this worked, I immediately started working on a similar upgrade that we could offer to all our current and future XRD users. I’ll detail my early progress in the next post.

All of the powder XRD (PXRD) systems we work with use either manually interchangeable aperture slits or automatic (stepper motor driven) slits to control divergence and scatter. One of the most common questions I hear from new users is “What is the ideal slit arrangement”. While I realize that there are many instruments out there with “one-size fits all” slits, the D500, D5000, D5005 and D8 optics are what I call “Research Grade”. This means that they can be adjusted and tuned for a particular application to maximize effects that are desirable and minimize those which are not. One of the most common reasons to change the anti-scatter and divergence slits is to reduce scatter over the sample at low angles. This scatter is the primary limiting factor for users who want to see diffracted peaks at very low angles. At Texray, we offer instrument time (data collection) as one of our services and have received requests for starting angles as low as 1 degree 2theta so it occurred to me that now would be a good time to collect some reference data and answer this question once and for all.

The image on the left shows the effect that the anti-scatter and divergence slits have on low angle scatter. The image on the right is of the two primary reflections of quartz (Novaculite) with the same slits. Note the intensity loss. The benefit of automatic slits is that they can be set very small at the beginning of the scan and gradually open up throughout the angular range. Very few users need that kind of flexibility, but since we’re talking about slits, it bears mentioning.

Low angle scans with various slits

This data was collected with matched slits set at 0.2mm, 0.6mm, 1mm and 2mm. These correspond to practical starting angles of 0.6, 0.9, 1.4 and 2.5 degrees 2theta respectively.

Low angle scans with various slits PEAK COMPARISON

Looking at the actual peaks, you can see the affect the smaller slits have on the rest of the data. These were collected without the benefit of a diffracted beam monochromator and with the primary soller slit removed. Neither of these factors would have a dramatic impact on the result, but the lack of a primary beam soller slit explains the asymmetrical peak shape in the second scan range pictured.