A comparative study of high-pressure behaviors of the two polymorphs of HoGeO.

Two polymorphs of polycrystalline HoGeO, 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 HoGeO, which is suggested to be associated with the breaking-up of long chains of the edge-shared polyhedron group HoO. By contrast, cubic HoGeO is stable at high pressures up to 33.3 GPa.