Ever since the discovery of large electromechanical response at the morphotropic phase boundary of the classical piezoceramic system ${\mathrm{PbZr}}_y{\mathrm{Ti}}_{1-y}{\mathrm{O}}_3$ (PZT) more than six decades ago, different variants of PZT are in use in wide-ranging applications. For the stability of electromechanical performance of piezoelectric devices against inadvertent temperature increase during device operation, the use of piezoceramics with a high Curie point is desirable. In general, chemical modifications of ferroelectrics that significantly improve their piezoelectric response lower the Curie point/depolarization temperature. In contrast to this general trend, here we report a phenomenon wherein a slight Eu modification of PZT, synthesized as per the nominal formula ${\mathrm{Pb}}_{1-3x/2}{\mathrm{Eu}}_x\left({\mathrm{Zr}}_{0.53}{\mathrm{Ti}}_{0.47}\right){\mathrm{O}}_3$, not only increases its piezoelectric charge coefficient $\left(d_{33}\right)$ remarkably from 204 pC/N $(x=0)$ to 415 pC/N $(x=0.005)$, but also increases the Curie point notably from 373 °C $(x=0)$ to 389 °C $(x=0.005)$. We report here this phenomenon and the underlying mechanism by investigating the structures at the local and global length scales using a combination of tools like $\mathrm{E}{\mathrm{u}}^{3+}$ photoluminescence, Raman spectroscopy, and x-ray powder diffraction. We found that while the increase in Curie point is caused by Eu-doping pushing the system from a two-phase (rhombohedral + tetragonal) state to a single-phase tetragonal state with increased tetragonality, the remarkable increase in the $d_{33}$ is associated with Eu-doping increasing the structural heterogeneity of the system by limiting rhombohedral correlations on the local scale. We reproduce the same phenomenon by doping PZT with a dilute concentration of Sm and La, thereby demonstrating the generality of this phenomenon.

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• Ferroelectricity
• Piezoelectricity
• Piezoelectrics
• Polycrystalline materials
• Photoluminescence
• Raman spectroscopy
• X-ray powder diffraction