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Film effects on XRD data

Posted by: Ken Stauver In: Uncategorized 27 Nov 2014 0 comments Tags: Bruker D5000, D500, D5000, D5005, D8, Diffraction, Diffractometer, Energy-dispersive detector, film, Jade, Jade 2010, Kapton, KS Analytical, Materials Data Inc, MDI, Mylar, Polycarbonate, Polyimide, Prolene, PXRD, X-ray, XRD, XRD data collection

Our 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.

Scotch “Magic” office tape. Adhesive side down.

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

Energy dispersive detectors for XRD systems

Posted by: Ken Stauver In: Uncategorized 20 Nov 2014 0 comments Tags: Bruker, D500, D5000, D5005, D8, Diffraction, Diffractometer, Energy-dispersive detector, KS Analytical, powder XRD, PXRD, X-ray, XRD, XRD data collection

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.

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.

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

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.

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

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.

Air-sensitive sample cells

Posted by: Ken Stauver In: Uncategorized 16 Nov 2014 0 comments Tags: Diffraction, Diffractometer, powder XRD, PXRD, reactive, sample preparation, X-ray diffraction

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.

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.

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.

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.