AN ANALYTICAL XRAY SERVICES LABORATORY
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You can never have enough sample holders no matter what machine you’re running. We’ve certainly found this to be true at Texray so we always try to keep a large number of them on-hand. KS Analytical Systems has always made one-off and custom sample holders for the Bruker instruments, but we’re now offering the standard PMMA powder holders as well at significant cost savings over the OEM version. The standard holder (25mm x 1mm deep well) is priced at $55 with bulk discounts starting at 20 holders.

Custom well depths, diameters, grooved floors, side-loading and zero-background versions are available.

Our PMMA holders are compatible with Bruker D8 Focus – D8 Advance (single, FlipStick autosampler, 90-position autosampler), D4 Endeavor and D2 Phaser (single only) systems. D500 and D5000 instruments can also use these holders.

We’ve brought the complete manufacturing process in-house to give us the freedom to make the custom designs our customer have always asked for. This includes custom laser etching. Company logos are a common request, but we’ve also started serializing sample holders on request. At Texray, we even etch them with barcodes for tracking samples through the data collection process.

The pictures below show a custom funnel tool for filling side-loading sample holders. The tool is machined from billet aluminum with an acrylic window on the funnel to make it easier to gauge fill level. The funnel itself is polished and the viewing plate which allows the users to see when the sample well is full is made of sapphire crystal for maximum scratch resistance.

It’s relatively common for us to receive very small volumes of material for analysis. Often this is the total amount available so getting the right answers is extremely important. When these come in as powders, the answer is always to run them on a zero background plate, but sometimes that’s not the case. Luckily, there are other options for analysis of very small quantities.

The most common application for filter-membrane sample holders has always been respirable silica quantification. This is mandated by OSHA and is an extremely common industrial hygiene test. Ambient air is sampled with a fixed or mobile suction system and particles are deposited onto a PVC membrane inside a sealed cartridge. Testing procedures are defined by NIOSH7500 and since this is a total quantification method (not a relative method), it’s critical that the entire sample is measured. Unfortunately, the measurement cannot be completed on the PVC membrane as received. Transferring the sample powder to an Ag membrane is accomplished by dissolving or ashing the PVC away, diluting the remainder in a solvent and depositing it onto the Ag membrane by vacuum filtration. The end result is an extremely low loss of analyte even for very small volumes of material.

This preparation method is also very useful for other types of samples which might have crystalline particulate suspended in a solution. Drying samples can be time-consuming, heating them to boil off liquid can cause phase transitions in the crystalline analyte, and handling dry powder in very small quantities is a very good way to lose material. Vacuum filtration solves all these problems.

 

Our most popular custom sample holder is the SC40F25 which is designed to hold the common 25mm Ag membrane filters used for this type of mounting. The anodized Al body is a time-tested design that works very well and causes almost no interference with the data, unlike the original injection-molded plastic parts. However, the most common method for retaining the membrane has always been to drop a metal support disk behind it and use an ID snap ring to retain both the disk and membrane. This can be a frustrating operation even for experienced hands. Snap rings are hard to control and the high spring tension gouges the inner diameter of the Aluminum body to the point that the holders must be replaced periodically.

After watching so many clients struggling with this system, we thought we could find a better option. The first step was a simple, laser cut acrylic backer instead of the metal disk. The acrylic was thicker which limited the depth to which the snap ring needed to be set. This was an improvement but still required the snap ring.

The next step was 3D printed plugs which could be pushed into the well. These supported the membrane and held it in the plane of diffraction at the same time. A standard pair of pliers was all the was needed to grab the plug and gently rotated it to release the membrane. This seemed like the ideal solution, but we heard from one user who claimed that the plug was causing an interfering peak in his measurements. We’ve been around the block with 3D printed sample holders in general and it’s definitely true that the common thermoplastics used will crystallize when cooled rapidly. This causes lots of problems for routine analysis of powders, but this was the first we’d heard of a peak being visible through an Ag membrane. Perhaps this user had a particularly thin membrane, but regardless, we needed a new solution, both for their lab and our own.

 

Our current solution is a laser cut “spring” backer which again combines the function of retainer and support in one part. The spring is easy to install by hand and can even be removed by hand, but forceps or needle-nose pliers make this easier. These have been working very well so we’re hopeful that this is going to be a long-term solution that we can share with our clients.

 

 

 

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.

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.

The majority of the samples we receive come in volumes high enough to completely fill the well in any of our standard sample holders. Some are too large or oddly shaped which calls for a special holding solution like those listed here, but many are simply very small quantities of powder. Placing these in a standard holder would leave them well outside the plane of diffraction and provide terrible data, not to mention substantial scatter
or diffracted background from whatever the powder is placed on. The answer is a zero background sample holder (ZBH). Most our users at KS Analytical Systems run the original Siemens/Bruker plates, but others are using Si(100) and even glass substrates. We’re very happy to say that
we’re able to offer a direct replacement for these with our new ZBH-32 holders. These fit most Siemens XRD systems and can be customized for use in most any other system. Contact us for more information on this. The scan below shows the data collected from a single mg of Silicon 640B standard powder spread across a ZBH.

Off Planar Quartz ZBH w-1mg 640B

Full scan of 1mg Silicon 640B standard spread across a ZBH

ZBH-32

ZBH-32 sample holders mounted for Siemens and Bruker single sample stages.

 

Some users report acceptable results using simple glass plates. While there are serious caveats here, it may be a reasonable solution for some users. The issue with amorphous glass is not diffracted peaks in the background, but rather, scatter off the surface. X-ray scattering off a surface is inversely proportional to the average atomic number of that material. That is to say, the lighter the matrix, the more efficiently it will scatter X-rays. This is why we use a pure Graphite sample to characterize the emission spectra of our XRF instrumentation. The glass sample shows the expected scatter “hump” starting at a very low angle and it doesn’t flatten until nearly 100°2Θ. While some of this can be modeled and subtracted with good profile fitting software like Jade 2010, it can be challenging to match the data quality of a good ZBH. We’re working on a series of videos to guide new users through some of these features, but on-site training classes are also available.

 

Glass plate

Amorphous glass empty

Glass-Qtz-Si510 overlay

Glass, ZBH-32 and off-planar quartz scans overlayed for comparison

 

 

 

 

 

 

 

 

Several of our customers in the geological industry use standard Si(100) wafers. These can be a great solution, but again have serious drawbacks for some applications. The Si(100) material creates diffracted peaks which are very sharp and therefore easier to model out sometimes, but also very high as the material is monocrystalline. The scan below shows what happens when one tries to run a normal scan across a bare plate. The largest peaks are actually only one or two which have over loaded the detector and caused it to drop out. All of these scans were collected with our SDD-150 which can handle up to 1×10^6 cps, but for the sake of good comparison, we left it tuned as it would be for a standard pattern. The monocrystalline nature of this material causes big problems, but it also allows for a creative solution. See the second scan for the results of the same measurement with the plate angled 1 degree off of theoretical. With this geometry, it’s unlikely this would affect the data quality dramatically, but the offending peaks are drastically diminished.

 

Si-100 wafer

Si-100 empty

Si-100 locked vs unlocked

Si-100 standard vs skewed scan

 

 

 

 

 

 

 

 

 

 

Off-planar Quartz holders have been the industry standard for decades. Historically, these have been made from solid, monocrystalline quartz material cut at a specific angle (6° off the C axis if I’m not mistaken). While these work well, they can be inconsistent. Even some of the OEM holders we’ve tested have shown some peaks which we can’t explain. Talking to some very experienced crystallographers, we find that they’ve had similar experiences.

 

 

Off Planar Quartz ZBH

Off-planar Quartz empty

ZBH-32 empty

ZBH-32 empty

 

 

 

 

 

 

 

 

We’ve been looking for a better answer for several years, but there are few off-the-shelf materials which work as well as off-planar quartz. The ideal answer was to cut solid Si(100) oriented billets such that the face presented to the diffractometer had no d-spacings which would diffract in the normal range of these machines. This is not unlike the off-planar Quartz method, but the starting material is much more consistent and durable. Si(510) offers very low background as well as the consistency of a manufactured product. The new ZBH-32 sample holders from KSA come in two versions, ZBH-25 and ZBH-32 with the latter being ideally suited for rotating stages and low angle work.

 

 

 

 

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.

 

Posted by: In: Uncategorized 25 Aug 2014 0 comments Tags: , , , , ,

The most common practice in powder XRD is to simply fill the recessed well of a sample holder with finely ground powder and start collecting data. That works for a great many users, but everyone is eventually faced with a more complicated situation at some point. At Texray, odd samples and special requirements are the norm. The photos below represent some of the common and not-so-common needs we’ve come across. Many of these are one-off designs fabricated by KS Analytical Systems.

20140825_143140The top row shows the three most common holders we see with various well depths. These are almost exclusively used for loose powders. The goal is to get the surface of the sample into the plane of diffraction with as little of the holder in the beam as possible. The plastic material has a very high scattering coefficient which creates a hump in the data around 13 degrees 2Theta. These are all designed for the 40-position sample changers from Siemens (now Bruker).

The second row gets more interesting with a special holder for high volume instruments. This was designed for magnetic handling and worked great as long as you don’t mind the low angle scatter problem of the plastic and aren’t working with ferrous powders.

The middle is one we use for collecting data from membrane filters. These are notoriously hard to hold down with any precision so they get mounted from the rear and held against a “lip” to keep them both flat, and in the plane of diffraction. They work wonderfully.

Next we have a simple side load sample holder. I’m a big fan of these and use them anytime I’m running loose powders on a single sample stage. It allows the user to load with a very smooth top surface that’s perfectly flat without creating any preferred orientation. Preferred orientation is frequently caused by pressure being applied to the basic top-load holders in an effort to get a flat surface. It is to be avoided whenever possible. Notice that the holders are all Aluminum at this point. Most custom holders are Al or a combination of Al and stainless steel depending upon the special properties desired.

The last row are good examples of odd-shaped sample holders. When you’ve got a rock with one flat surface or a little chip of some material, you still need to keep it in the plane of diffraction. The user simply places a ball of clay in the middle of the holder, the sample goes on top of that and then a glass plate is used to crush the clay (with the sample on top) down such that everything is in plane with the elevates posts. These posts interface with the machine to define the plane of diffraction right across their surface, thus the sample is right where it needs to be without any complicated engineering or microscopic adjustments.

 

Custom holders for a D500 user. Side load as well as top-load in Al.

Custom holders for a D500 user. Side load as well as top-load in Al.

Side load precision without the possibility of powder falling out at low angles.

Side load precision without the possibility of powder falling out at low angles.

Vacuum holding is common when working with semiconductors or other materials with very consistent thicknesses.

Vacuum holding is common when working with semiconductors or other materials with very consistent thicknesses.

We needed to keep our standards in our desiccator cabinet as well as store membrane filters long-term. Custom laser-cut shelves make this easy.

We needed to keep our standards in our desiccator cabinet as well as store membrane filters long-term. Custom laser-cut shelves make this easy.

A typical run of custom sample holders for a high volume XRD operation. This user actually has a custom loading tool that allows for multiple holders to be filled simultaneously.

A typical run of custom sample holders for a high volume XRD operation. This user actually has a custom loading tool that allows for multiple holders to be filled simultaneously.

This is a completely custom stage designed to hold a large thrust bearing race such that the bottom of the groove is in the plane of diffraction for retained austenite and residual stress measurements.  The bearing is held in place by magnets.

This is a completely custom stage designed to hold a large thrust bearing race such that the bottom of the groove is in the plane of diffraction for retained austenite and residual stress measurements. The bearing is held in place by magnets.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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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.

 

 

 

 

 

 

 

 

 

 

 

 

XRD work is categorized into two major groups. Single crystal and powder analysis. While single crystal work is usually highly customized to particular applications and involves a largely unique hardware set, powder (PXRD) work covers a broad range of applications. Many of which can be performed without any special hardware at all. Perhaps it would be more accurate to call it “Randomly oriented small particle” diffraction. Somehow I think “ROSPXRD” would be slow to catch on. At the risk of oversimplifying the options, I’d like to take a few posts to showcase some of the more common analyses which can be performed with a basic PXRD system and perhaps a few that require minimal additional attachments.

This is an example of a Bruker D8 Advance configured in its most basic PXRD state with only a scintillation counter, sample stage and source.

This is an example of a Bruker D8 Advance configured in its most basic PXRD state with only a scintillation counter, sample stage and source.

This is the same D8 base instrument configured for single crystal XRD. Note the Chi, phi, XYZ stage, area detector (2D) and Goebel focusing mirrors.

This is the same D8 base instrument configured for single crystal XRD. Note the Chi, phi, XYZ stage, area detector (2D) and Goebel focusing mirrors.

 

 

 

 

 

 

 

 

 

 

 

My last post involved a basic phase identification and this seemed like a great place to start. Most PXRD users are asked to identify some unknown bit of corrosion, rock or contaminant at some point. I once took a shot at something which later turned out to be sewage sludge ash. I have no idea what they hoped to find in that. Exotic, mundane or distasteful, the most basic XRD can collect the necessary data to perform this analysis. Phase ID is usually the first step most users take toward more advanced software. In addition to the simple pattern analysis features that usually come standard, you’ll need an engine designed to search one of the many commercial or open-source databases available. The ICDD, NIST and AMCSD are probably the most popular with several others on the fringe. There are even user-developed databases which are usually compiled in a particular lab to cover the range of phases they expect to see based on their product or application.

Limiting the search to categories of phases which are likely to be present greatly improves the relevance of the results list. There’s obviously no reason to search through a huge list of minerals when trying to identify a metallic oxide coating. Hit lists can also be refined based on data from other sources such as qualitative elemental analysis. We use our WDXRF systems and the built in elemental filter in Jade to trim the options substantially.

Any good search/Match engine will have support not only for multiple databases, but also offer the option to limit your search to certain subfiles which are group my material categories.

Any good search/Match engine will have support not only for multiple databases, but also offer the option to limit your search to certain subfiles which are group my material categories.

Semi-quantitative or simple qualitative elemental data can be used to eliminate a large percentage of erroneous hits so the analyst can focus on only pertinent options. We prefer to bundle an XRF scan with any Phase ID project.

Semi-quantitative or simple qualitative elemental data can be used to eliminate a large percentage of erroneous hits so the analyst can focus on only pertinent options. We prefer to bundle an XRF scan with any Phase ID project.

 

 

 

 

 

 

 

 

 

 

Isolating the valid hits from erroneous is where experience comes into play. Non-ideal particle size, preferred orientation and crystallographic imperfections can make the process quite difficult. Relative peak intensity ratios, peak width and sometimes even the complete absence of a particular peak which would theoretically be present all present opportunities to gain additional insight. Sometimes this is relatively easy as in the case I presented in the previous post, but other situations are not so simple. These difficulties are amplified in the case of low concentrations and complex mixtures.

This is a great example of Phase ID the way we all wish it came out. The peaks are sharp, intense and located right on their theoretical angle.

This is a great example of Phase ID the way we all wish it came out. The peaks are sharp, intense and located right on their theoretical angle.

This is an example of something a little harder to nail down. Overlapping peaks, several additional phases and a highly imperfect sample. Refining the options based on external measurements and in depth sample prep make the difference between success and failure in cases like this.

This is an example of something a little harder to nail down. Overlapping peaks, several additional phases and a highly imperfect sample. Refining the options based on external measurements and in depth sample prep make the difference between success and failure in cases like this.

 

 

 

 

 

 

 

 

 

 

XRD pattern analysis has come along way in the last 40 years and most of the major improvements have come on the heels of increased computing capability which enables us to perform exhaustive iterative calculations on complex patterns quickly and at comparatively low cost. However, there is nothing on the market as of now which has made an experienced analyst obsolete.