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. Author manuscript; available in PMC: 2016 Mar 1.
Published in final edited form as: Mater Sci Eng R Rep. 2015 Mar 1;89:1–48. doi: 10.1016/j.mser.2015.01.002

Figure 21.

Figure 21

Polarization elongation and polarization compression. (a) Schematic polarization elongation and polarization compression in a perovskite unit cell ABO3 with rhombohedral (R) phase, whereby the polarizations are represented by arrows. When polarization compression is strong enough, ferroelectric-paraelectric phase transition may be induced. (b). Gibbs free energy profile for PZT with Zr/Ti ratio 60/40 at 540 K and 300 K. An easier polarization elongation process can be expected at a higher temperature 540 K, which is closed to the Curie temperature where ferroelectric-paraelectric phase transition. (c) A lead-free piezoelectric ceramic system, BZT-BCT. High piezoelectric activity was observed for optimal composition at room temperature, accounting for the facilitated composition-driven-polarization-rotation and temperature-driven-polarization-elongation/compression. (d) A designed system that exhibits compositionally driven-phase transitions with easy paths for both polarization rotation and polarization elongation/compression. Adapted from Refs. [33, 127].