In situ high-pressure x-ray diffraction of the two polymorphs of Sc₂Ge₂O₇

Pyrochlore-type (P-type) and thortveitite-type (T-type) Sc2Ge2O7 were prepared through different methods. The phase stability and compressibility of the two polymorphs of Sc2Ge2O7 were studied using in situ synchrotron x-ray diffraction. An irreversible phase transition of monoclinic (C2/m) T-type Sc2Ge2O7 induced by a pressure of 4.8 GPa was observed. However, the cubic (Fd-3m) P-type Sc2Ge2O7 can resist a much higher pressure of up to 30.6 GPa.