Microstructural, ferroelectric, and photoluminescent properties of (100)-oriented Sm³⁺-doped Na_0.5Bi_0.5TiO₃ thin films

(100)_C-oriented Na_0.5Bi_{0.5- x}Sm_xTiO₃ (NBST) lead-free ferroelectric thin films were prepared on Pt/Ti/SiO₂/Si substrates by chemical solution deposition method, and their microstructural, dielectric, ferroelectric, and photoluminescent properties were studied. X-ray diffraction and scanning electron microscopy analysis indicated that both the grain size and (100)_C orientation degree of NBST thin films were decreased by doping Sm³⁺ ions. Raman spectra showed that structural symmetry of NBST thin films decreased at low Sm³⁺ doping concentration and then increased at high doping concentration of Sm³⁺ ions. An appropriate amount of Sm³⁺ dopants was confirmed to enhance dielectric and ferroelectric properties of the NBST thin films. Among all the compositions, the Na_0.5Bi_0.492Sm_0.008TiO₃ thin film exhibited the largest remnant polarization (2P_r) of 27.3 μC/cm² and high dielectric constant of 1068, as well as a low dielectric loss of 0.04. Temperature- and frequency-dependent dielectric characteristics illustrated the relaxor ferroelectric behavior of Na_0.5Bi_0.492Sm_0.008TiO₃ thin film. Meanwhile, the Na_0.5Bi_0.492Sm_0.008TiO₃ thin film also showed optimal orange-red emission at 600 nm, which is originating from the ⁴G_5/2 → ⁴H_7/2 transition of Sm³⁺ ions.