Rapid stability of ferroelectric polarization in the Ca, Ce hybrid doped BaTiO₃ ceramics

In this work, we report a rapid stability phenomenon of ferroelectric polarization in the Ca, Ce hybrid doped BaTiO₃ ceramics (BCaxT+BTCe8) (x = 10, 20, 24, 30 mol%) prepared by separate doping Ca²⁺ and Ce⁴⁺ ions. Double hysteresis loops are identified in the aged BCaxT+BTCe8 samples; meanwhile, the polarization of these loops present a rapid decrease within very short aging time (about 1 h), and then the polarization remains almost unchanged over the followed ~1000 h. This phenomenon is not reported in previous researches. Raman scattering spectrum indicates that oxygen vacancies are generated because of Ca²⁺ ions entering into Ti sites partly in the BCaxT+BTCe8 samples, and then the oxygen vacancies are quantitatively characterized by half of the Ce³⁺ content through the XPS test. The emergence of the aging phenomenon is explained through the defect dipole reorientation mechanism. The larger radius of Ca²⁺ ions is further discussed as a possible reason for the rapid stability phenomenon of ferroelectric polarization. It may provide an effective design method from the viewpoint of the ionic radius to accelerate polarization stability, and thus to facilitate the possible practical applications of the aging effect.