Reliable temperature sensing based on intense green upconversion emissions of Y2Mo4O15:Yb3+,Er3+ under 980 nm excitation

In this paper, Y2Mo4O15:Yb3+/Er3+ upconversion phosphors are prepared by a co-precipitation method. In the case of 20% Yb3+ doping, the intense green upconversion luminescence is obtained, which can be attributed to the energy transfer from Yb3+-MoO42- dimer to Er3+ that suppresses the multi-phonon relaxation of I-4(11/2) to I-4(13/2). Similar the Yb3+ sensitization, the dimer sensitization is also dependent on the Yb3+ concentration. When the Yb3+ concentration exceeds 20%, the luminescence is quenched by the cross relaxation and energy migration between dimers. A method for evaluating the reliability of temperature measurement standards is reported. Moreover, in term of the reliable temperature scale, the maximum absolute sensitivity of sample doped with 20% Yb3+ is determined to be 0.0117 K-1. Favorable sensing ability and strong upconversion luminescence indicate that the optimum sample is potentially applicable as the optical thermometric materials.