Phase transformation of germanium nitride (Ge3N4) under shock wave compression

The phase transformation behavior of hexagonal germanium nitride, including both α- and β-Ge3N4, has been studied under shock wave compression. The shock compressed quenched samples indicate phase transformation from hexagonal into a cubic spinel structure (γ-Ge3N4). This transformation is completed with increasing shock pressure up to 40–46 GPa (temperature of 1300–1500 K). The lattice constant of γ-Ge3N4 is measured to be 0.820 63±0.000 19 nm, and the crystal density 6.581 g/cm3, by the powder x-ray diffraction. The stability of γ-Ge3N4 also has been investigated under shock wave compression. It is found that the spinel structure is very stable, and up to at least 63 GPa (temperature of ∼1700 K) there is no indication of the formation of a postspinel phase.