Near-infrared to short-wavelength upconversion temperature sensing in transparent bulk glass ceramics containing hexagonal NaGdF_4: Yb^3+/Ho^3+ nanocrystals

Abstract

Transparent glass ceramics containing hexagonal NaGdF4: Yb3+, Ho3+ nanocrystals were successfully fabricated via self-crystallization, which was further confirmed by XRD, TEM, HRTEM, and STEM-HADDF, as well as upconversion (UC) emission spectra. Impressively, GC750 exhibited fascinating upconversion luminescence, and the corresponding 5F1/5G6 and 5F2,3/3K8 states of Ho3+ were proven to be thermally coupled energy levels (TCELs), resulting in high temperature-sensitive behaviors based on fluorescence intensity ratio (FIR) for optical thermometry. As a consequence, a high relative sensitivity of 1.43%·K−1 at 390 K was achieved, offering a great potentially application in optical thermometry.