**4. Conclusions**

PMN-PT thin films with different Fe doping concentrations have been synthesized on Pt/Ti/SiO2/Si substrate by the CSD technique. The crystallinity, orientation, microstructure and defect dipoles induced by ion substitution were attributed to the origin of the enhanced electrical performances; 2% Fe-doped PMN-PT thin film annealed at 650 ◦C showed the high (111) preferred orientation, and the preferred orientation transferred to random orientation as the doping concentration increased. The dense columnar structure was obtained in 2% Fe-doped PMN-PT thin film annealed at 650 ◦C. The excessive annealing temperature and excessive doping concentration will lead to appearance of cracks. In addition, compared with the pure PMN-PT thin film, the effectively enhanced leakage characteristic was obtained in 2% Fe-doped PMN-PT thin film, which is because of the reduction of movable *V*•• *<sup>O</sup>*2<sup>−</sup> concentration and restraint from Ti4+ to Ti3+. The enhanced ferroelectric (*P*<sup>s</sup> = 78.8 μC/cm2, *P*<sup>r</sup> = 23.1 μC/cm2, *E*<sup>c</sup> = 100 kV/cm) and dielectric properties (*ε*<sup>r</sup> ~1300 at 1kHz) have been obtained in 2% Fe-doped PMN-PT thin film annealed at 650 ◦C. These results provide the important guiding significance for controlling the grain orientation in preparation of ferroelectric thin films and enhancing the electrical performances of ferroelectric thin films.

**Author Contributions:** Conceptualization, C.F. and S.H.; methodology, C.F.; validation, C.F.; formal analysis, C.F.; investigation, C.F. and T.L.; data curation, C.F. and X.B.; writing—original draft preparation, C.F.; writing—review and editing, C.F.; funding acquisition, C.F. and S.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Shandong Postdoctoral Innovative Talents Support Plan (Grant No. SDBX2020010), National Natural Science Foundation of China (Grant No. U1806221), the Project of "20 Items of University" of Jinan (Grant No. 2019GXRC017), and Synergetic Innovation Center Research Project (Grant No. WJGTT-XT2).

**Conflicts of Interest:** The authors declare no conflict of interest.
