Temperature sensing based on upconversion luminescence of Er3+/Tm3+-Yb3+ doped Ca4Y6Si4O24 phosphors

To explore new upconversion (UC) phosphor materials for optical temperature sensing, a series of Er3+/Tm3+-Yb3+ doped Ca4Y6Si4O24 samples were designed by using solid-state reaction method. The phase purity was examined via XRD patterns, which indicates the obtained phosphors are single-phase. The UC spectra of CYS:1% Er3+,xYb(3+) (0 <= x <= 20%) reveal the green and red emission peaks of Er3+ show different change rate in intensity when the Yb3+ concentration increases, which can be owing to the cross-relaxation between Er3+ and Yb3+. For the Tm3+-Yb3+ doped CYS, the optimal Yb3+ concentration was determined to be 10 mol%. Different strategies were employed for temperature sensing behavior. The investigation indicates that the best sensor sensitivity was obtained in the CYS:1%Er3+,10%Yb3+ sample by employing the fluorescence intensity ratio technique with non-thermally coupled levels. The above results could be instructive to the development of new luminescent materials with high sensitivity.