High pressure phase boundaries of AgNbO3

The external pressure is one of the essential parameters for regulating the structure and energy conversion properties of antiferroelectric AgNbO3. For pure AgNbO3, however, there has been still a blank of its real lattice structure under the stress field. Here, high-pressure lattice structures and phase transitions of AgNbO3 have been explored by spectroscopic experiments and theoretical models. A successive phase transition process from Pbcm to C2221 to P21 has been observed at the pressure range of 0–30 GPa, associated with displacive-type characterized by soft-mode kinetics. Note that the paraelectric phase cannot be achieved under high-pressure at room temperature. Significantly, the competition of long-range Coulomb force, short-range interatomic interaction, and covalent interaction in AgNbO3 lattice were demonstrated under the stress field. The present work can provide fundamental guidelines to reveal the high-pressure phase transitions of AgNbO3, which will open up possibilities for the designing device with functional properties at extremes.