Effects of rare earth dopants on the EO properties and domain configurations in PMN-PT transparent ceramics

To comprehend the relationship between the dopants, structure, and properties of EO materials, transparent ceramics of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ doped with rare earth (RE) ions (Er³⁺, Eu³⁺, La³⁺, and Sm³⁺) were prepared via pressure-free sintering. The transmittance of completely dense and pore-free La-doped PMN-PT ceramics is significantly better than that of the other RE-doped PMN-PT. The optimal composition of 2-mol% La-doped 0.75PMN-0.25PT has the largest electro-optical (EO) coefficient of 42.1 × 10⁻¹⁶ m²·V⁻² and highest transmittance of 69% in the near-infrared band, which exceeds the performance of the vast majority of PMN-PT ceramics reported in the past. As the dopants vary among Er³⁺, Eu³⁺, La³⁺, and Sm³⁺, the polar domain distribution undergoes a disorder–order–disorder transformation. The study investigated the effects of various dopants on the microstructure, transmittance, EO properties, domain structure, and polarization behavior of PMN-PT ceramics. On the macroscopic polarization scale, the exceptional EO performance observed in the La-doped PMN-PT ceramics is due to the presence of an ordered lamellar polar nanodomain structure, which facilitates easier and faster polarization switching. On the atomic-level scale in relation to the dopants, the largest ionic radii and tolerance factor with moderate electronegativity for La-doped case is believed to be favorable for the highest EO effect. These results suggest that a defect-engineered well-ordered distribution of polar nanoregions could enhance the EO effect. Overall, our research provides valuable insights for the design of high-performance EO materials based on domain configuration and doping engineering.