Temperature sensing behavior of Tm³⁺: ¹G₄(a), ¹G₄(b) in oxyfluoride glass ceramics containing BaYb_xY_(1-x)F₅ nanocrystals

Tm³⁺-doped transparent oxyfluoride glass ceramics containing BaYb_xY_(1-x)F₅ nanocrystals were prepared via high temperature solid phase melting method, of which up-conversion emission is achieved by the Yb³⁺-mediated energy transfer process. The required photon number of Tm³⁺ ions emissions in BaYb_xY_(1-x)F₅ nanocrystals was calculated through the luminescence spectra, revealing the strong dependence of energy transfer mechanism on Yb³⁺ ions concentration. Meanwhile, based on the fluorescence intensity ratio technology, the effect of different energy transfer mechanism on the temperature sensitivity was investigated by the temperature-dependent luminescence intensity of thermally coupled energy levels of Tm³⁺: ¹G₄(a), ¹G₄(b). The obtained sensitivity decreases with the increase of Yb³⁺ ions content, which is mainly attributed to the changes in photon absorption process of Tm³⁺: ¹G₄(b).