Laboratory preparation of high-temperature phases

In general, high-temperature phases are prepared in the laboratory by 

If material can be lost by volatilization, as with phases containing alkalis, fluoride, or sulphate, it may be necessary to use a sealed platinum container and to test its effectiveness by chemically analysing the product. Control of the furnace atmosphere, e.g. by employing mixtures of CO and CO2 to buffer the oxygen pressure, may be needed if variable oxidation states are possible, as with iron compounds. Special methods may be needed to make single crystals of sufficient size for X-ray structure deterniinations or other purposes. These are described in papers on X-ray structure determination. Single crystals of C3S can be obtained from CaClj melts (NIO). 

---