Near-infrared to short-wavelength upconversion temperature sensing in transparent bulk glass ceramics containing hexagonal NaGdF4:Yb3+/Ho3+ nanocrystals

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 F-5(1)/(5)G(6) and F-5(2,3)/K-3(8) 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. (C) 2017 Optical Society of America