A comparative study of high-pressure behaviors of the two polymorphs of Ho2Ge2O7

Abstract

Two polymorphs of polycrystalline Ho₂Ge₂O₇, one with tetragonal structure and the other with cubic structure, were synthesized by using different methods. The structural stabilities of these two polymorphs under high pressure were investigated by angle-dispersive X-ray diffraction (ADXRD). Pressure-induced amorphization was found in the tetragonal Ho₂Ge₂O₇, which is suggested to be associated with the breaking-up of long chains of the edge-shared polyhedron group Ho₄O₂₀. By contrast, cubic Ho₂Ge₂O₇ is stable at high pressures up to 33.3 GPa.