Up-conversion luminescence and optical temperature-sensing properties of Er3+-doped perovskite Na0.5Bi0.5TiO3 nanocrystals

• NBT:Er nanocrystals were prepared by hydrothermal method.
• A two-photon absorption mechanism in the upconversion emission process is proposed.
• The temperature-sensing properties of the NBT:Er nanocrystals is demonstrated.
• The sensitivity of the nanocrystals is higher than that of its bulk form.

In this work we demonstrate the preparation of Er3+ doped perovskite ferroelectric Na0.5Bi0.5TiO3 nanocrystals and their application in temperature sensing. The samples were synthesized via a facile hydrothermal method. Upconversion emission at 528 nm and 547 nm from two thermodynamically coupled excited states of Er3+ were recorded in the temperature from 80 K to 480 K under the excitation of a 980 nm diode laser. The emission intensity ratio (I528/I547) as a function of the temperature was investigated. A sensitivity of 0.0053 K−1 is observed at 400 K, suggesting they are promising candidate for nanothermometers.