Enhancement of polarization property of PZT film by ion-substitution using rare-earth elements

Rare-earth-substituted lead zirconate titanate thin films were synthesized to improve the ferroelectric properties of lead zirconate titanate through the enhancement of its crystal anisotropy. Thin films of Pb_1.00-(3x/2)o- RE_x(Zr_0.40Ti_0.60)O₃ [RE-PZT(A)] and Pb_1.00RE_x(Zr_0.40T_i0.60) _1-(3x/4)O₃ [RE-PZT(B)] with RE = La or Dy were deposited on (111)Pt/Ti/SiO₂/(100)Si substrates by chemical solution deposition (CSD). Rare-earth-substitution did not affect the crystal orientation of the PZT-based films where the PZT(111) plane was oriented along the surface-normal direction. Dy³⁺ substitution based on DyPZT(B) up to x = 0.02 enhanced the crystal anisotropy (c/a) and remanent polarization (P_r) of PZT films simultaneously, while both c/a and P_r values of Dy-PZT(A) decreased as x increased continuously. On the other hand, La ³⁺ substitution degraded the ferroelectric properties gradually in both the case of La-PZT(A) and (B). The Dy³⁺ ion could be substituted for a B-site in a PZT crystal preferentially, and that promoted the crystal anisotropy and the ferroelectric properties of PZT films.