Enhanced dielectric, ferroelectric, and optical properties in rare earth elements doped PMN-PT thin films

Rare earth (RE = La³⁺, Sm³⁺, Pr³⁺) ion doped Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (RE-PMN-PT) ferroelectric thin films with compositions near the morphotropic phase boundary were grown on the Pt/TiO₂/SiO₂/Si(100) substrate using sol-gel/spin coating method. The phase structure, electrical properties, and photoluminescence performance of thin films were investigated systematically. The highly (100)-preferred orientation was obtained in pure perovskite Sm-PMN-0.30PT thin films with an average grain size of 131 nm. After 2.5% Sm³⁺ doping, the PMN-0.30PT thin films exhibited a triple enhancement of dielectric permittivity with a maximum value of 3500 at 1 kHz, a low dielectric loss of 1.3%, and high remanent polarization of 17.5 μC/cm² at room temperature. In visible light and near-infrared band, the transmittance rate increased with PT content and showed the highest value of 85% in 2.5%Sm-PMN-0.31PT. In addition, the films presented strong red-orange emission at 599 nm, which was sensitively in temperature range of 248-273 K corresponding to the rhombohedral to monoclinic phase transition temperature.