Synthesis of Spherical Na(La, RE)(MoO4)2 (RE = Eu/Yb, Er), Up/Down Conversion Photoluminescence and Optical Thermometry

Abstract

In this work, spherical Na(La,RE)(MoO[Formula: see text] (RE = Eu/Yb-Er) double molybdates were prepared using the rare earth hydroxide (La,RE)(OH)SO4 as a self-sacrificing template. The composition, structure, morphology, up/down conversion luminescence and fluorescence lifetime (FL) of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fluorescence spectrophotometer, and Fourier transform infrared (FT-IR) spectrophotometer. The results indicate that highly pure spherical Na(La,RE)(MoO[Formula: see text] (RE = Eu/Yb-Er) samples can be obtained from the proposed route. The room temperature and temperature-dependent up/down conversion luminescence properties of the resulting Na(La,RE)(MoO[Formula: see text] (RE = Eu/Yb-Er) phosphors were analyzed in detail. The temperature-sensing performances for the two phosphors in both fluorescence intensity ratio (FIR) and FL modes were evaluated. Classical down and up-conversion photoluminescence (PL) from Eu[Formula: see text] and Er[Formula: see text] were observed. The down conversion phosphors were proved to be capable of sensing temperature via FL mode, and the maximum absolute sensitivity [Formula: see text] and maximum relative sensitivity [Formula: see text] were found to be [Formula: see text][Formula: see text]K[Formula: see text] (298[Formula: see text]K) and [Formula: see text][Formula: see text]K[Formula: see text] (523[Formula: see text]K), respectively. The up conversion phosphors Na(La,Yb,Er)(MoO[Formula: see text] were well capable of sensing temperature via FIR mode through thermally coupled 2H[Formula: see text], 4S[Formula: see text] levels (I[Formula: see text]/I[Formula: see text], and the maximum absolute sensitivity [Formula: see text] and maximum relative sensitivity [Formula: see text] were found to be [Formula: see text][Formula: see text]K[Formula: see text] (523[Formula: see text]K) and [Formula: see text][Formula: see text]K[Formula: see text] (348[Formula: see text]K), respectively.