High pressure phase boundaries of AgNbO_(3)

The external pressure is one of the essential parameters for regulating the structure and energy con-version properties of antiferroelectric AgNbO_(3).For pure AgNbO_(3),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 AgNbO_(3)have been explored by spectroscopic experiments and theoretical models.A successive phase transition process from Pbcm to C222_(1) to P2_(1) 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 AgNbO_(3)lattice were demonstrated under the stress field.The present work can provide fundamental guidelines to reveal the high-pressure phase transitions of AgNbO_(3),which will open up possibilities for the designing device with functional properties at extremes.