Exploring antiferroelectric domain and antiphase boundaries stabilities of PbZrO3 through in situ heating transmission electron microscopy

The lead zirconate PbZrO3 has been studied for a long time now. However, despite the fact that PbZrO3 is considered as the archetypical antiferroelectric material, many questions remain such as : What is the structure of the PbZrO3 at room temperature ? Is there an ferroelectric phase but reaching the cubic one ? What is the nature of antiphase boundaries and at what temperature will they disappear ? Are they linked to the antiferroelectric domains ? To answer to these questions, we used transmission electron microscopy coupled to the Fusion Select Protochips® TEM holder to probe in temperature the phase transitions, the existence and the stability of antiphase boundaries in bulk PbZrO3. Single crystals of PbZrO3 have been prepared by focused ion beam (FIB) on a thermal chips provided by Protochips®. The structural characterization has been performed on a FEI Titan3 G2 80-300 microscope, operated at 300 kV, equipped with a Cs probe corrector and by using the Fusion Select Protochips® TEM holder. The experiments were performed by coupling electron diffraction, TEM and STEM imaging during thermal cycles from room temperature to 300°C. As expected by macroscopic measurements, TEM temperature-dependent measurements on the PbZrO3 single crystal revealed a phase transition from the antiferroelectric state to an intermediate phase without any change in the domain size. Then above a certain temperature, all the domains suddenly disappear at the formation of the cubic phase. When cooling the specimen down to room temperature, the sample phenomenon appears. The homogeneous single cubic-phase domain suddenly splits into many domains. These domains don’t exhibit any 4-cell periodicity characteristic of the antiferroelectric phase but instead the same intermediate phase order than during the increase. Few degrees lower, dipoles rearrange and form the 4-cell periodicity, as observed for the initial state. The stability in temperature of antiphase boundaries in the antiferroelectric domains will be discussed as well as the effects of the TEM acceleration voltage on them and the domain stability. All these results were compared to previous ones obtained on 40-nm-thick PbZrO3 thin film.