Antiferroelectricity and ferroelectricity in A-site doped silver niobate lead-free ceramics

AgNbO3-based ceramics have been considered as promising lead-free materials for energy storage applications. The antiferroelectricity stability is a key factor for energy storage performance, which can be affected by Goldschmidt tolerance factor (t), phase structure and so on. The competition between t and phase structure was designed in A-site doped AgNbO3 ceramics. Li-doping leads to reduced t and a phase transition from monoclinic antiferroelectric phase to rhombohedral ferroelectric phase. Na-doping results in decreased t without phase transition. K-doping causes a phase transition from monoclinic antiferroelectric phase to orthorhombic ferroelectric phase. The enhanced ferroelectricity in (Ag1-xLix)NbO3 and (Ag1-xKx)NbO3 ceramics is due to the appearances of rhombohedral and orthorhombic phase, respectively. The enhanced antiferroelectricity in (Ag1-xNax)NbO3 ceramics is attributed to the decreased t. By analyzing t, phase structure and antiferroelectricity/ ferroelectricity, it seems that the phase structure is dominating in determining the ferroelectricity/antiferroelectricity rather than t in A-site doped AgNbO3 ceramics.