I suppose you are using quartz tubes... Seal them under vacuum and everything will be ok. Make sure you have left enough empty space in the tube - the sulphides tend to explode (possess high vapours pressure). See any paper for synthesis of sulphide based chalcogenide glasses for further clues.

I agree with Dr. Hristove-Vasileva. The standard approach is to seal your raw elements in a quartz ampoule under vacuum with an oxy-acetelene (or similar) torch before melting. For sulfide glasses, I strongly recommend not filling the ampoule more than 50% to prevent explosions during melting, especially with compositions containing excess sulfur.

Dear Dr. Musgraves and Dr. Vasileva thanks for your valuable answers. It is so much informative for my work. Here I want to ask one more question I am using Na2S.9H2O and P2S5 compounds for the synthesis of glass. But in other literature people are using Na2S instead of Na2S.9H2O. I am not able to use Na2S because its too costly. So here I want to use Na2S.9H2O instead of Na2S. Kindly suggest me how much it will influence on synthesized materials.

The presence of the H2O will dramatically impact your IR transparency, if that is a consideration for you. The OH resonance vibration at ~3.3 microns can be expected to absorb almost all of the transmitted light in this case. Additionally, you may experience some severe crystallization, depending on your exact composition and how close it is to the edge of the glass forming region. If you have particular properties you are interested in, I may be able to give a more detailed answer. Also, you may want to view "Thermal poling behavior and SHG stability in arsenic-germanium sulfide glasses" in Optical Materials Express to help understand the impact of the sodium.

I fully agree with Dr. Musgraves - the synthesized materials will differ significantly from the desired ones. Furthermore, the presence of H2O totally excludes the melt quenching technique. The water will cause oxidation, if somehow the ampoule stays intact. I suggest you try to find some methods for obtaining of Na2S (this is a material, which I am not familiar with). Probably this will be much cheaper than buying the already synthesized one.

This might help: http://www.sciencedirect.com/science/article/pii/S0022459605800854 ?

http://www.google.com/patents/US6582675

Thanku very much Dear Dr. Musgraves and Dr. Vasileva. Here I am making the glasses as solid electrolytes for Sodium ion batteries at room temperature. I think so in synthesized materials ionic conductivity will be better. If there is any problem kindly suggest me.