Transitions from soft to hard piezoelectricity of (Ba, Ca)(Ti, Zr)O₃ceramics via precipitation hardening

Hard piezoelectrics are essential for high-power applications, the market share of which has increased significantly over the past few years. Acceptor-doping hardening, which relies on oxygen vacancies, has been proven to be a good practice to improve mechanical quality factors. However, the high mobility of oxygen vacancies restricts the use of acceptor-doping hardening to low driving fields and temperatures. Here, we extend the design of hard-type piezoceramics via precipitation hardening and demonstrate its large potential in (Ba,Ca)(Ti,Zr)O3. A soft-to-hard transition has been realized in (Ba,Ca)(Ti,Zr)O3 ceramics with an introduction of precipitates, where the mechanical quality factor and coercive field increase by over 180% and 120%, respectively. Through synchrotron x-ray diffraction and Rayleigh analysis, it is revealed that the hardening effect is attributed to the inhibition of domain wall motion by the intragranular CaTiO3 precipitates. This precipitation-hardening approach offers great potential for the design of hard piezoceramics.