In situ transmission electron microscopy study on Nb‐doped Pb(Zr_0.95Ti_0.05)O₃ ceramics

Abstract

The ferroelectric-to-ferroelectric phase transition between the high temperature (FE RH ) and the low temperature (FE RL ) rhombohedral phases in a Nb-doped Pb(Zr 0.95 Ti 0.05 )O 3 ceramic was investigated with transmission electron microscopy (TEM). Both bright field images and electron diffraction patterns were monitored as a function of temperature as well as dc electric field. A special TEM specimen holder that permits the application of electric voltage up to 600 V was employed for the study of electric field-induced phase transition. It was found that both [1/2] (011) (Jaffe et al., 1971). It has been shown that the FE RH ? FE RL transition is manifested by the doubling of the perovskite unit cell, with the space group changing from R3m to R3c (Glazer et al., 1978). In compositions that are further closer to PbZrO 3 , an antiferroelectric phase with the space group Pbam becomes stable (Jaffe et al., 1971;Woodward et al., 2005). At ambient conditions, Pb(Zr 0.95 Ti 0.05 )O 3 is at the antiferroelectric/ferroelectric phase boundary. A small amount of Nb (usually 2 at %) is often used to stabilize the ferroelectric phase in this composition (Yang et al., 2005). As a consequence, ferroelectric $ ferroelectric and ferroelectric $ antiferroelectric phase transitions can be easily triggered in these ceramics.External electric fields are known to be capable of triggering antiferroelectric-to-ferroelectric Pan et al., 1989;Yang and Payne, 1992) and relaxor-to-ferroelectric Ye and Schmid, 1993) phase transitions in various Pb-based perovskite compounds. In these field-induced transitions, the electric field aligns the short-range ordered electrical dipoles to the external field direction, stabilizing the ferroelectric phase with long-range dipole order. In ferroelectric single crystals, strong electric fields along a nonpolar axis have been found to rotate the polarization vector. The rotation of the polar axis changes the symmetry of the crystal, leading to a field-induced ferroelectric-to-ferroelectric phase transition (Park and Shrout, 1997;Wada et al., 1999;Zhao et al., 2007).

Effect of uniaxial stress on ferroelectric behavior of (Bi1/2Na1/2)TiO3-based lead-free piezoelectric ceramics

“…The presence of superlattice spots in perovskite oxides indicate a doubling of the unit cell and it has been attributed to either cation ordering or oxygen octahedra tilting. 26,27 Since cation ordering is not likely to occur in these ceramics, [28][29][30] the electron diffraction results indicate that BNT-FE is rhombohedrally distorted, most likely with the R3c space group, [28][29][30] and BNT-AFE displays a pseudocubic perovskite structure with, at the moment, unknown octrahedra tilting. A mixed tilting system, either a combination of in-phase and antiphase tilting or a two phase mixture of one antiphase and one in-phase tilting, is possible.…”

The Antiferroelectric ↔ Ferroelectric Phase Transition in Lead‐Containing and Lead‐Free Perovskite Ceramics

“…In addition, the R 3 c phase is characterized by the presence of superlattice diffraction spots because of the oxygen octahedral tilting . It has been shown in a similar composition (Pb 0.98 Nb 0.02 Zr 0.95 Ti 0.05 ) that the superlattice spots disappear under applied electric field, indicating the removal of the tilts of oxygen octahedra. It should also be noted that the detilting of oxygen octahedra under electric loadings as a mechanism for the auxetic behavior shares similarity with the rigid unit model for the negative thermal expansion in ZrW 2 O 8 …”

Optimization of energy storage and electrocaloric performance in Pb(Zr,Ti)O3 via A-Site La and Bi Co-doping

“…Developing ferroelectric-based cooling devices is essential to identify materials that operate at low fields and cover a wide temperature range around room temperature. Several solid-solution families have been proposed as potential replacements for EC applications, such as lead zirconate titanate (PZT) [23][24][25], lead lanthanum zirconate titanate (PLZT) [26,27], (K, Na) NbO 3 [28][29][30], Bi 1/2 Na 1/2 TiO 3 [31][32][33] and BaTiO 3 (BT) [34][35][36] solid solutions. The PZT family, in particular, has undergone extensive testing for EC properties in various forms, such as single crystals, thin films and bulk ceramics.…”