As we know, Li2S is very sensitive to moisture which makes it difficult to characterize. I have managed to do XRD by pasting Kapton tape on the powder but this process does not work for Raman (because the wavelength of the laser is too large to penetrate the kapton tape). Thanks in advance for your suggestions.
Other ways to protect air-sensitive materials are to coat them with some dry mineral oil (for example, oil that sodium metal has been stored in) or a little paraffin wax, although I am not sure these would work with your laser either.
The best solution consist to introduce the powder into a glass cell and to remove the air before sealing. The glass is transparent and gives small raman scattering.
If you' are willing to go to the extra trouble, you will want to prepare your sample in a glove box with inert atmosphere and seal it in a box or bag with a sapphire or quartz window (you should be able to use the Kapton tape around the edges of the window for a decent seal). While glass has been suggested above as a window material, it does interfere somewhat - sapphire and quartz are significantly better since they have well defined peaks where SiO2 has a rather broad one. When you focus the laser, make sure it's on the sample under the window and not the window itself. From my experience this can be a little tricky. Good luck!
Put the powder on the glass slide and compress it by hand with another glass slide, perform several measurements. If you will find disagreement with the literature results perform the same procedure only this time put it on the hot side of the Peltier element. No rush for complicated setup, just try =)
Thanks everyone for your kind response. I think all your suggestions help me to do the Raman analysis for my samples.
A clear plastic bag, a source of dry nitrogen gas as an improvised glove box an Quartz cuvette from a UV-VIS is perfect these can be sealed with a stopper/sides and the flat sides make it easy to focus through. You will need a long working distance objective. We routinely use this for air sensitive samples. The other is sealed ampules (you need a blow torch, capillaries and patience).
You could also try sealing the moisture sensitive material into a thin capillary, and then use them for analysis like XRD & Raman. It works good too !!!
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