Comparison of upconversion luminescent properties and temperature sensing behaviors of β-NaYF4:Yb3+/Er3+ nano/microcrystals prepared by various synthetic methods

In this paper, Yb 3+ /Er 3+ co-doped hexagonal NaYF 4 have been successfully synthesized by solvothermal, thermal decomposition, hydrothermal and molten salt method, respectively. The crystal structures, particle morphologies, sizes and corresponding upconversion luminescent properties of β-NaYF 4 :Yb 3+ /Er 3+ nano/microcrystals are systemically studied. It is interesting to observed that the temperature-dependent UC luminescent properties of β-NaYF 4 :20 %Yb 3+ , 2 %Er 3+ samples are strongly related to their synthesis methods. Comparison of the upconversion luminescence and thermal sensitivity between the β-NaYF 4 :Yb 3+ /Er 3+ samples reveals that β-NaYF 4 :Yb 3+ /Er 3+ sub-microplates synthesized by thermal decomposition method have much stronger green emission intensity, better luminescent thermal stability and higher temperature sensitivity. This findings are relevant to the application of β-NaYF 4 :Yb 3+ /Er 3+ in optical temperature sensors and to the further understanding of the UC luminescent mechanism.