Supported by the National Natural Science Foundation of China (Grant Nos. 51922083, 52072092, 52172129), Professor Fei Li’s group in Xi’an Jiaotong University and collaborators have made progress in the research of lead zirconate titanate ceramics. The research was published in Science on April 7, 2023, with the title “Lead zirconate titanate ceramics with aligned crystallite grains”. (Article link: http://www.science.org/doi/10.1126/science.adf6161).

Lead zirconate titanate [Pb(Zr, Ti)O₃, PZT] ceramics have been the dominant materials in various electromechanical devices, due to their high piezoelectric performance and relatively wide temperature usage range. The piezoelectricity of PZT ceramics determines the key parameters (e.g., sensitivity and resolution) of electromechanical devices, such as medical imaging transducers and high-precision actuators, thus further improving the piezoelectric properties of PZT ceramics is of great importance for the development of next-generation electromechanical devices and systems. Engineering ceramic grains along a specific crystallographic orientation (i.e., fabricating textured ceramics) enables the utilization of physical property anisotropy, which provides an effective way to further enhance piezoelectric properties of PZTs. However, the progress in fabricating textured PZT ceramics has been very slow since 1990s. Specifically, serious solid-state reaction between the PZT powder and commonly used titanate templates (BaTiO₃ and SrTiO₃) hinders the template-induced grain growth process during the sintering process, leading to great difficulties in the fabrication of high-quality textured PZT ceramics.

To resolve the above challenge, Prof. Fei Li’s group propose a seed-passivated texturing process to fabricate the textured PZT ceramics. First, a new type of barium zirconate titanate [Ba(Zr, Ti)O₃, BZT] templates is developed to replace the generally used titanate templates, which improves the stability of the templates in the PZT matrix. Second, a multilayer architecture of PZT matrix with different Zr⁴⁺ concentration is designed to replace the generally used uniform matrix, which not only ensures the template-induced grain growth in Ti-rich PZT layers but also facilitates desired homogeneous composition through interlayer diffusion of Zr/Ti during sintering.

The research team resolves the long-standing challenge of fabricating textured rhombohedral PZT ceramics by suppressing the otherwise severe chemical reaction between PZT powder and titanate templates. For the first time, the high-quality <001>-textured PZT textured ceramics were successfully fabricated (Figure 1a & b) with PZ content up to 70%. Moreover, significantly enhanced piezoelectric and electromechanical properties (piezoelectric coefficient d₃₃~700 pC/N, g₃₃~90 mV·m/N, electromechanical coupling coefficient k₃₃~0.85) and good temperature stability (Curie temperature ~360ºC) are achieved in the textured PZT ceramics with the composition near morphotropic phase boundary, which resolves the dilemma that the piezoelectricity and Curie temperature can only be enhanced at the expense of each other for PZT ceramics. (Figure 1c).

This work provides a generalized route to fabricate textured ceramics that have not yet been manufactured due to the inevitable chemical reaction between the template and ceramic powder. The newly developed high-performance PZT textured ceramics will not only benefit the R&D for various electromechanical devices such as high-sensitivity sensors and transducers, but also offer basic materials for investigating the structure-property relationship of the PZT ferroelectric solid-solution.

Figure 1 (a) Cross-sectional SEM image of a PZT textured ceramic; (b) The {002} pole figure obtained from the synchrotron XRD experiment; (c) Piezoelectric coefficient d₃₃ as a function of Curie temperature for both PZT-based textured ceramics and representative state-of-the-art piezoelectric ceramics.