Unique dielectric tunability of Ag(Nb1−xTax)O3 (x = 0–0.5) ceramics with ferrielectric polar order

Abstract

The dielectric tunability and hysteresis loops of Ag(Nb1−xTax)O3 (x = 0–0.5) ceramics were characterized at room temperature with various bias electric fields to determine the polar order. When the maximum bias electric field is 75–125 kV/cm, the dielectric constant and dielectric loss first decrease and then rise with increasing the bias electric field for x = 0 (AgNbO3). The unique response was analyzed and addressed to a mixed response of ferroelectricity (FE)-like and antiferroelectricity (AFE)-like tunable properties, and is explained by the ferrielectricity (FIE) of AgNbO3. Similar dielectric tunability was also observed for x = 0.2 and 0.35, while the dielectric constant and dielectric loss increase monotonously with bias electric field for x = 0.5, indicating the transition in polar order from FIE to AFE for Ag(Nb1−xTax)O3 ceramics with increasing Ta content. The results are consistent with the M1 (Pmc21)-M2 (Pbcm) phase transition at x = 0.4. In comparison, AFE-like double hysteresis loops could not be observed with the applied electric field up to 125 kV/cm, which proved that the tunability measurement is a much more sensitive tool for determining the polar order compared to hysteresis loop measurement.