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.