Mechanism of grain growth and excellent polarization, dielectric relaxtion of La³⁺, Nd³⁺ modified PZT nano-films prepared by sol–gel technique

Ferroelectric PbZr_0.52Ti_0.48O₃ film and its partial substitutions by rare earth ions La³⁺ and Nd³⁺ Pb_0.9(La/Nd)_0.1Zr_0.52Ti_0.48O₃, grown on Pt(111)/Ti/SiO₂/Si(100) substrates, were prepared via sol–gel and rapid thermal processes. Structural characterization by X-ray diffraction and scanning electron microscopy showed that Pb(Zr_0.52Ti_0.48)O₃ and Pb_0.9La_0.1(Zr_0.52Ti_0.48)O₃ films are of (111) preferred orientation but Pb_0.9Nd_0.1(Zr_0.52Ti_0.48)O₃ is more inclined to (100) reflection though both are of tetragonal perovskite structure. The results indicate that the piezoelectric properties of PZT thin films can be improved by doping La³⁺ and Nd³⁺ substituted A-site. The d₃₃ can be dramatically improved by doping La³⁺. Moreover, Pr of Pb(Zr_0.52Ti_0.48)O₃ films reaches up to 120.53 µC/cm², while the doping samples present relatively inferior ferroelectric hysteresis loops (Pr_La = 64.32, Pr_Nd = 53.17 µC/cm²), greater dielectric constants, higher dielectric loss and lower leakage current than the undoped Pb(Zr_0.52Ti_0.48)O₃ sample. And meanwhile, the samples showed a typical non-Debye dielectric spectroscopy of multiple quantum relaxation time distribution observing from the Cole–Cole plot at room temperature.