Tungstate and molybdate phosphors have received great attention for their excellent photoluminescent properties and thermal stabilities. In the article, Tb3+-activated tungstate and molybdate green phosphors were prepared by a solid-state reaction method at different caline temperatures and were compared and studied. The crystal structures and the morphologies of samples were characterized by X-ray diffraction (XRD) patterns and field emission scanning electron microscopy (FE-SEM) images. The energy-dispersive spectra (EDS) proved the compositions of the prepared samples. The photoluminescence (PL) spectra showed that the PL excitation spectra of Tb3+-doped Lu2W3O12and Lu2Mo3O12green phosphors consisted of a broad and strong charge transfer band (CTB) and 4f–5d transitions of Tb3+in the ultraviolet (UV) wavelength range and some narrowed excitation peaks from the 4f–4f transition of Tb3+in the near ultraviolet (NUV) wavelength region. The PL emission spectra of the phosphors exhibited the characteristic green emissions owing to the5D4→7F5transition of Tb3+located at about 547 nm. The values of energy gapEgwere calculated based on the diffuse reflection spectra (DRS). The measuring temperature-dependent PL spectra illustrated the thermal stabilities of phosphors. The Tb3+-doped Lu2Mo3O12phosphor presented normal thermal quenching phenomena and the values of the thermal activation energyEawere calculated based on the measuring temperature dependent PL emission spectra. The Tb3+-doped Lu2W3O12phosphor exhibited abnormal thermal enhancing CTB excitation intensity at about 170 °C. Furthermore, the PL decay curves suggested that the lifetime corresponding to the5D4level of Tb3+in the Lu2W3O12host lattice was longer than that in the Lu2Mo3O12host lattice. Compared the Tb3+-doped Lu2Mo3O12phosphor, the Tb3+-doped Lu2W3O12phosphor has shown potential as an application in temperature sensors.
Jie Yang,Jiujun Zhu,Laihui Luo,Wei Xie,Weiping Li,Peng Du
To settle the thermal quenching and dissatisfied sensitivity of luminescent materials, a series of Tm 3+ /Yb 3+ /Sc 3+ -tridoped Lu 2 W 3 O 12 upconverting microparticles was synthesized through sol-gel method. In-situ X-ray diffraction results reveal that the resultant samples have good negative thermal expansion (NTE) properties, which can be improved by Sc 3+ doping. Upon 980 nm excitation, the final products can emit brightness upconverison (UC) emissions and their intensities can be enhanced by Yb 3+ and Sc 3+ doping. Moreover, the temperature-dependent UC emission spectra suggest that the designed compounds possess anti-thermal quenching luminescence. Specially, these UC emissions from 1 G 4 , 3 F 2,3 and 3 H 4 levels show different responses to temperature, allowing their feasibilities in optical thermometry. Via utilizing the fluorescence intensity ratio technique to analyze the temperature-associated UC emissions from non-thermally coupled levels (non-TCLs), one knows that maximum absolute and relative sensitivities of developed upconverting microparticles are 0.124 K –1 and 3.105%/K, respectively, while those of the resultant upconverting microparticles are 4.895×10 –5 K –1 and 1.774%/K, respectively, when the TCLs are used. Our findings verify that the utilization of NTE effect is an efficient route to induce the anti-thermal quenching UC luminescence, and the thermometric properties of luminescent materials can also be regulated by selecting proper sensing strategy, spatial mode and doping content.
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