Structural, ferroelectric, and optical properties of Pr-NBT-xCTO relaxor ferroelectric thin films

Sol-gel method was used to prepare the Pr3+ ions-doped (1-x)Na0.5Bi0.5TiO3-xCaTiO(3) (Pr-NBT-xCTO) (x = 0, 0.04, 0.06, 0.08, 0.1, 0.12, and 0.16) thin films on Pt/Ti/SiO2/Si and fused silicon substrates. The structure phase of thin films was evolving from rhombohedral (R3c) to orthorhombic (Prima) with increasing CTO content. Owing to the morphotropic phase boundary (MPB), the improved ferroelectric and dielectric properties were obtained at x = 0.06-0.1. The MPB was formed from the concomitant phase of rhombohedral (R3c) and orthorhombic (Prima). The Pr-NBT-0.08CTO thin film showed the best ferroelectric and dielectric properties, as well as strong relaxor behavior (the diffusion factor is gamma = 1.79). In addition, all the films exhibited strong red emission as excited by UV light, and wide optical band-gap (3.44-3.47 eV), which might be influenced by grain size and structural variation. Our results indicate that Pr-NBT-xCTO thin films may have potential applications in ferroelectric-luminescence multifunctional optoelectronic devices.