I never used such tape. The term tape suggests a rather thick cover. Thus, foil sounds generally better to me.

We analyse a lot of covered samples. Kapton foil works fine for us.

Hi Daniel,

I am not sure what is the energy range you work at.

In any case if you are using commercial kapton tape, the minimum thickness is around 7 microns. I have used much thinner kapton tapes, as thin as 1 micron. I used to make them myself. It is relatively simple if you have a spinner and an oven which goes up to 400 deg C. I think I was able to get a quote from luxel. In any case if you are working in the soft x-ray range Beryllium is a good candidate, you can get it as thin as 7 microns at lebow company, and you just have to be a little careful with it, and not to breath its dust particles etc.

If you are interested to get the instructions to produce thin kapton foils, mail me and I will send it to you.

just thinking out loud here...

I don't have such samples but, has anybody tried mixing such air sensitive powders with a little grease to protect from environment and then smearing the mixture on a Si low background holder? I use grease to hold some difficult samples onto Mylar foil for transmission work, so I wondered if the sample was enclosed in a grease whether this would suit your purpose. Its a cheap solution.

As i said earlier, we had so far no major problems with kapton foil. We take a foil supplied by the manufacturer of our diffractometer together with the corresponding specimen holders for air-sensitive samples.

Ian mentioned mylar. This could be an alternative to kapton. To my knowledge you can get mylar foil of approx 3µm. Mylar creates peaks but perhaps not at positions you are interested in.

Generally, if possible you should try foils from several sources. Not only the thickness might change, also the scattering pattern might differ.

Have you tried performing XRD in transmission mode? That was the only way I could avoid having the peaks from the film and obtained a very clean spectrum. Depending on the diffractometer you have at your disposal, transmission configuration is very simple to use and the quantity of sample necessary for the test is very small (a few miligrams). The sample is "sandwiched" between two mylar or kapton foils (both of them work well, using commercial thicknesses). Maybe, using capillary tubes might be an option too. In reflection mode, it's quite difficult to minimize the influence of the plastic film.

I agree with Renan, the transmission method should be the best choice.

Did you think about using oil instead? In single crystal diffraction I immerse crystal in Paratone oil or NVH oil before mounting them on cappilary. It prevents from solvent evaporation and works as a glue between crystal and capillary. I don't know however how high the background would be when  your powder was completly coverd with a droplet of this oil.

A colleague used "Scotch Magic Tape" as a cover material. It's a cellulose based sticky tape without any sharp reflexes but just some "hump" around 2Theta = 20° - 30°. Any other sticky tape is based on polypropylene or other polymers which show strong and sharp reflexes.

Pro: It's cheap, widely available and shows no reflexes

Con: It's fairly thick

You can use mylar foil. I used in some cases also the polyethilene films that in Italy we used to cover the food (Domopack films, commercial name, you can buy it in a supermarket). This film is amorphous and you can collect the blank sample pattern and substract this pattern from that of your sample. You can try, it is a very inexpensive procedure...

I saw some people used the glass capillary method. I have one minor question unclear: the diffractometer is  a single crystal X-Ray or Powder X-ray?

Thanks

You can try Ultralene. This is used to measure Sulfur XAS.

We use Quartz slide and drop some nitrocellulose (kind of a binder) on top of it followed by nanoparticles. It gives pretty good spectra.

I prefer magic scotch tape