ZrSiO4 and coesite were obtained under high-pressure and high-temperature from the nano precursor of a-SiO2 and ZrO2. XRD and Raman measurements indicate that ZrSiO4 was formed at a temperature higher than 920 ℃ under a pressure of 3.6 GPa. As the pressure increased to 3.9 GPa, the ZrSiO4 formation temperature was reduced to 815 ℃. The formation temperature for coesite was 990 ℃ under 3.9 GPa. The lower formation temperature for ZrSiO4, as compared to that for coesite, provided an experimental evidence that the coesite in the Earth＇s surface usually occurs as inclusions in ZrSiO4.
