Pure and strong red photoluminescence from Na0.5Gd0.5TiO3: Eu ferroelectric thin films under ultraviolet light excitation

Abstract

A series of novel photoluminescent ferroelectric thin films Na0.5Gd0.5TiO3: xEu (NGT: Eu) with various Eu3+ doping concentrations were prepared at various heat-treated temperature, which have single pseudo-cubic perovskite structure at proper heat-treated temperature from 700 °C to 800 °C according to X-ray diffraction results. There existed narrow and intensive emission bands located at red light region ascribed to 5D0 → 7F2 and 5D0 → 7F1 transitions of Eu3+ by 283 nm excitation. The strong energy absorption of NGT host and efficient energy transfer to Eu3+ should be primarily responsible for the emissions. Gd3+ acts as sensitizer which has an important role on the energy transfer from the host NGT to Eu3+. The luminescence from NGT: 0.25Eu thin films is the strongest for all the NGT: Eu films, and its color coordinate is (0.65, 0.32) close to ideal red light. The quenching concentration in NGT: Eu films reaches as high as 25%. The lifetime of emissive energy level Eu3+: 5D0 in NGT: 0.1Eu and NGT: 0.5Eu thin films is 1.024 ms and 0.931 ms, respectively. Finally, the ferroelectric property of NGT: 0.25Eu thin films was tested and the remanent polarization (2Pr) is 7.10 μC/cm2 lower than that of Na0.5Bi0.5TiO3.