Ceramics of composition Ag_1−3xBi_xNbO₃ (0.005 ≤ x ≤ 0.040) were prepared by solid state methods and their structure and electrical behavior were characterized with a view to their potential use as high power energy storage materials.

Triangular voltage waveform was employed to distinguish the contributions of dielectric permittivity, electric conductivity and domain switching in current-electric field curves. At the same time, it is shown how those contributions can affect the shape of the electric displacement — electric field loops (D–E loops). The effects of frequency, temperature and microstructure (point defects, grain size and texture) on the ferroelectric properties of several ferroelectric compositions is reported, including: BaTiO₃; lead zirconate titanate (PZT); lead-free Na_0.5K_0.5NbO₃; perovskite-like layer structured A₂B₂O₇with super high Curie point (T_c); Aurivillius phase ferroelectric Bi_3.15Nd_0.5Ti₃O₁₂; and multiferroic Bi_0.89La_0.05Tb_0.06FeO₃. This systematic study provides an instructive outline in the measurement of ferroelectric properties and the analysis and interpretation of experimental data.

Grain size effects on the physical properties of polycrystalline ferroelectrics have been extensively studied for decades; however there are still major controversies regarding the dependence of the piezoelectric and ferroelectric properties on the grain size. Dense BaTiO₃ ceramics with different grain sizes were fabricated by either conventional sintering or spark plasma sintering using micro- and nano-sized powders. The results show that the grain size effect on the dielectric permittivity is nearly independent of the sintering method and starting powder used. A peak in the permittivity is observed in all the ceramics with a grain size near 1 μm and can be attributed to a maximum domain wall density and mobility. The piezoelectric coefficient d₃₃ and remnant polarization P_r show diverse grain size effects depending on the particle size of the starting powder and sintering temperature. This suggests that besides domain wall density, other factors such as back fields and point defects, which influence the domain wall mobility, could be responsible for the different grain size dependence observed in the dielectric and piezoelectric/ferroelectric properties. In cases where point defects are not the dominant contributor, the piezoelectric constant d₃₃ and the remnant polarization P_r increase with increasing grain size.

Ag(Nb_0.8Ta_0.2)O₃ is used here as a model system to shed light on the nature of the low temperature phase behavior of the unsubstituted parent compound AgNbO₃, which is an important material for high-power energy storage applications.