Incommensurately Modulated Polar Structures in Antiferroelectric Sn‐Modified Lead Zirconate Titanate: The Modulated Structure and Its Influences on Electrically Induced Polarizations and Strains

Abstract

Zrn.,,Snn.,S),.,sTi,lo, (PZST 45/y/2), have been studied by hot-stage transmission electron microscopy (TEM), dielectric spectroscopy, Sawyer-Tower polarization (P-E) measurements, and electrically induced strain (E-E) techniques. The compositional range chosen for investigation was 0 < y < 0.09. Electron diffraction confirmed the existence of $( 110) superlattice reflections in the previously designated antiferroelectric tetragonal state. For PZST 451012, the room-temperature modulated structure was found to be commensurate with the lattice and isomorphous with the antiferroelectric orthorhombic phase of PbZrO,. With increasing Ti content, the modulation wavelength (A) increased and became incommensurate. At high temperatures, A was found to be incommensurate for all compositions. A model is discussed which suggests that the origin of incommensuration is due to a competition between antiferroelectric and ferroelectric tendencies. P-E studies revealed antiferroelectric-ferroelectric (AFE-FE) polarization curves which possessed no hysteresis in the incommensurate region, indicating a thermally reversible AFE-FE transformation. On cooling, strong hysteresis developed as the incommensurate structure became metastably locked. Investigations then revealed that the electrically induced strain associated with the AFE-FE transformation was not realized until field strengths were attained significantly above that required for polarization saturation. It is believed that the electrically induced strain is decoupled from the polarization due to AFE-FE switching by the field modulation of the incommensurately modulated polar structure.

In situ transmission electron microscopy study of the electric field-induced transformation of incommensurate modulations in a Sn-modified lead zirconate titanate ceramic

“…The structural origin for these superlattice reflections is still under debate. 2,[5][6][7]9,21 However, the present in situ TEM study provides valuable insight into the physics mechanism for the presence of these superlattice reflections. It is clear in Fig.…”

“…These results are consistent with previous observations from other researchers. [5][6][7] In order to determine the field level needed for the in situ TEM study and to assess the sample geometry effect on the field-induced antiferroelectric-to-ferroelectric phase transformation, a dimpled and annealed 3-mm-diam disk specimen was tested for the hysteresis measurement and the result is also plotted in Fig. 3.…”

Antiferroelectricity induced by electric field in NaNbO3-based lead-free ceramics

“…Figure 4(b) displays the changes of the characteristic antiferroelectric {21 3 4 } superlattice peak. In the virgin state with the mixed antiferroelectric and ferroelectric phases, this peak is clearly seen.…”

“…[2][3][4][5][6][7][8] Most studied antiferroelectric ceramics in literature are based on the prototype compound PbZrO 3 with a perovskite structure, in which the phase transition manifests itself in the development of a large polarization and is generally accompanied by a significant volume expansion when the applied field exceeds a critical magnitude E F . [2][3][4][5][6][7][8][9][10] The associated volume change at the phase transition has been explored as a mechanism for toughening the ceramic. 11 Recently, it has been reported that some chemically modified PbZrO 3 -based ceramics can exist either in the antiferroelectric or ferroelectric state at room temperature, depending on their thermal history.…”

“…1(b) and 1(c), these two peaks are apparent in ANKN0, ANKN1, and ANKN2 but completely disappear in ANKN4. According to a previous neutron diffraction study, 17 these are the characteristic antiferroelectric superlattice peaks that can be indexed as {11 3 4 } and {21 3 4 }. Therefore, the as-sintered ceramics of ANKN0, ANKN1, and ANKN2 are antiferroelectric while ANKN4 is ferroelectric at room temperature.…”