Ferroelectricity in Silver Perovskite Oxides

There are two silver perovskite oxides: AgNbO3 and AgTaO3. AgNbO3 has a noncentrosymmetric group of Pmc21 at room temperature with a ferri-electric ordering of polarization. Such a ferri-electric state with small polarization can be changed into a ferroelectric state with very large polarization by a high electric field or by a chemical modification. The induced ferroelectric phase shows promising electromechanical response for applications in piezoelectric devices. In contrast, AgTaO3 is a quantum paraelectric, but ferroelectricity also can be induced through chemical substitution. The findings of good ferroelectric and piezoelectric performance in the silver perovskites are hoped to trigger further theoretical and experimental investigations on these systems.