Dual-stimuli in-situ TEM study on the nonergodic/ergodic crossover in the 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 relaxor

The existence of a variety of phases and their transitions in the electric field-temperature (E-T) space of relaxor ferroelectrics make them an interesting research subject. To directly observe the evolution of domain morphology and crystal symmetry in ferroelectrics under either temperature change or an applied electric field, in-situ transmission electron microscopy (TEM) is often the preferred characterization technique. Accessing all the phases in the E-T space of a relaxor crystal requires in-situ TEM with capabilities of simultaneous heating and biasing. In this letter, such a dual-stimuli in-situ TEM technique is demonstrated on 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO(3), a relaxor ceramic with a thermal depolarization temperature T-d of about 40 degrees C. Not only the domain structure change during thermal depolarization is directly seen, but also different microstructural responses under an applied electric field in the nonergodic and ergodic states are observed. The results prove that the dual-stimuli in-situ TEM technique is indispensable for exploring the rich physics in functional materials.