Effect of La on piezoelectric properties of Pb(Ni_1/3Sb_2/3)O₃–Pb(ZrTi)O₃ ferroelectric ceramics

Piezoceramic compositions Pb_1−zLa_z(NiSb)_0.05[(Zr_0.52Ti_0.48)_1−Z/4]_0.95O₃ with Z = 0.01–0.05 were synthesized by mixed oxide route to study the effect of Lanthanum (La) on crystal structure, microstructure, piezoelectric and ferroelectric properties. Calcination was performed at 1,060 °C and sintering at 1,270 °C for 1 h. X-Ray diffraction pattern indicated the polycrystalline microstructure along with co-existence of tetragonal and rhombohedral perovskite phases. Dielectric constant (\( K_{3}^{T} \)) was increased whereas piezoelectric voltage constant (g ₃₃) was decreased with increase in lanthanum. Dense microstructure was observed for the composition containing 3 mol% of lanthanum. This was resulted in optimum piezoelectric charge constant (d ₃₃ = 468 × 10⁻¹² C/N), electromechanical coupling factor (k _p  = 0.68), remanent polarization (P _r = 24.65 μC/cm²) and displacement (D = 2,012 nm). Results indicated that the composition Pb_0.97La_0.03(NiSb)_0.05[(Zr_0.52Ti_0.48)_0.9925]_0.95O₃ could be suitable for actuator applications. The composition Pb_0.98La_0.02(NiSb)_0.05[(Zr_0.52Ti_0.48)_0.995]_0.95O₃ resulted into moderately high value of voltage constant (g ₃₃ = 39.3 × 10⁻¹² V m/N) and optimum value of Figure of Merit (d ₃₃ × g ₃₃ = 16.2 × 10⁻¹² C V m/N²) indicated the usefulness for sensor and power harvesting applications.