Photoluminescence and thermometry properties of upconversion phosphor NaBiF4: Yb3+/Tm3+

Upconversion (UC) luminescent materials have received much attention due to their unique luminescent properties and potential applications in various fields. Yb3+/Tm3+ codoped NaBiF4 UC material has been successfully synthesized through a solvothermal method. With the excitation of 980 nm laser light, NaBiF4:Yb3+/Tm3+ powder show strong UC luminescence. Especially, the near-infrared (NIR) UC emission band of NaBiF4:Yb3+/Tm3+ centered at 800 nm is 49 times stronger than the blue emission band. The temperature-dependent UCL properties of NaBiF4:Yb3+/Tm3+ were investigated systematically under 980 run excitation. The results show that all the UC emission peaks of NaBiF4: Yb3+/Tm3+ in the region from 300 to 900 nm decrease with the temperature increase except for the emission peak at 697 nm which is positively correlated with temperature. And the UC emissions of NaBiF4: Yb3+/Tm3+ exhibits high temperature sensitivity between 303 and 443 K. Therefore, NaBiF4: Yb3+/Tm3+ material with strong NIR UCL could be a potential candidate for sensitive temperature sensor.