Unveiling the mechanism of substitution-induced high piezoelectric performance in PLZT ceramics

Ferroelectric lead zirconate titanate (PZT, PbZr_1-xTi_xO₃) dominates piezoelectric ceramic market due to high piezoelectric coefficients, high thermal stability and low processing cost. Doping of PZT with Lanthanum&nbsp;has been widely used to develop advanced piezoelectric ceramics with improved piezoelectric properties. However, the effects of La doping are ambiguous in literature and associated mechanisms are unclear. Here, we prepared La-doped PZT ceramics with different concentrations of La (PLZT) by the conventional solid state reaction method. The PLZT ceramics has a perovskite structure, where tetragonal (<em>P</em>4<em>mm</em>) and monoclinic (<em>C</em>1<em>m</em>1) phases coexist. Upon La-doping, the Curie point (<em>T</em>_c), ferroelectric lattice distortion and concentration of oxygen vacancies decrease. Under applied electric field, both domain switching and field-induced transition are observed. The remnant polarization (<em>P</em>_r) of the doped PLZT ceramics is found to be higher than that of the starting PZT ceramics, and the increased <em>P</em>_r is attributed to the substitution-reduced oxygen vacancies. With increasing temperature, the piezoelectric <em>d</em>₃₃ coefficient of the La-doped ceramics increases due to the increase of permittivity. The prevailing effect of high permittivity is linked with the high <em>d</em>₃₃value (~ 375 pC/N) of the x=0.5 ceramic. These findings unveil the mechanisms associated with La-doping in PZT ceramics, thereby providing a viable approach to developing advanced piezoelectric ceramics with high piezoelectric performance.