**2.4 Melt method**

One method often employed is to melt the reagents together and then later anneal the solidified melt. If volatile reagents are involved these are usually put in an ampoule that is evacuated (the reagent mixture is kept cold – by keeping the bottom of the ampoule in liquid nitrogen, e.g.) and then sealed. The sealed ampoule is then put in an oven/furnace and given a certain heat treatment.
