Effects of Nb doping on structural and electrical properties on PZT thin films

Lead Zirconate Titanate (Pb[Zr$_{\mathrm{x}}$T$_{\mathrm{1-x}}$]O$_{\mathrm{3}})$, known as PZT, is a piezoelectric material, widely used in memory applications, sensors and actuators. A major challenge for PZT is the accurate determination of its structural properties, which are ultimately responsible for improved functionality. We studied the structural properties, such as lattice strain, ferroelectric displacements and piezoelectric hysteresis, of PZT and Nb-doped PZT (Pb[Nb$_{\mathrm{y}}$(Zr$_{\mathrm{1-x}}$Ti$_{\mathrm{x}})_{\mathrm{1-y}}$]O$_{\mathrm{3}})$, known as PNZT. We used high-resolution X-ray diffraction and Bragg coherent diffraction. Under an external electric field, PZT and PNZT thin films show significantly different ferroelectric hysteresis behavior of polarizations. We tentatively attribute these differences to the role of Nb defects in PZT and its effects on the nature of the ferroelectric domains and domain walls.