Ho 3+ /Yb 3+ co-doped PbTiO 3 nanocrystals with different content of dopant were successfully prepared via a facile hydrothermal method. The purity, morphology, element distribution, chemical state and up-conversion (UC) photoluminescence (PL) of PbTiO 3 nanocrystals affected by Ho 3+ dopant are investigated systematically. X-ray diffraction (XRD) results illustrate that PbTiO 3 samples with the doping Ho 3+ concentration ranging from 0 to 5 mol-% are perovskite structure. The doping Ho 3+ ions have no change on the crystal structure of perovskite PbTiO 3 . Owing to the non-equivalent substitution of Ho 3+ to Ti 4+ in PbTiO 3 , the particle size of Ho 3+ /Yb 3+ co-doped PbTiO 3 samples is decreased as well as the particle agglomeration is detected. Moreover, Ho and Yb ions have uniform distributions in the PbTiO 3 nanoparticles as the presence of Ho 3+ and Yb 3+ cations. The up-conversion spectra demonstrate that Ho/Yb co-doped PbTiO 3 samples have up-conversion emissions centered at 550 nm, 660 nm and 755 nm, corresponding to the transitions of 5 F 4 ( 5 S 2 )→ 5 I 8 , 5 F 5 → 5 I 8 and 5 S 2 ( 5 F 4 )→ 5 I 7 of Ho 3+ ions. Additionally, the effect of temperature on the UC PL property of Ho 3+ /Yb 3+ co-doped PbTiO 3 system is further investigated. The sensitivity and the trend of Ho 3+ /Yb 3+ co-doped PbTiO 3 samples in temperature from 298 k to 493K are calculated on the basis of fluorescence intensity ratio (FIR) method. Ho 3+ /Yb 3+ co-doped PbTiO 3 nanocrystals are verified the high potential in the optical temperature sensing.
Yao Wang,Ning Guo,Yanmei Xin,Jing Li,Ruizhuo Ouyang,Baiqi Shao,Yuqing Miao
The synthesis conditions of most phosphors doped with lanthanide ions with d–f transition require a reducing atmosphere. The doping Bi3+ ions selected in this study perfectly avoid this requirement, and they are environmentally friendly and safe. Nevertheless, the spectral tuning of Bi3+ is a great challenge that limits its application. Herein, by regulating the value of x in the new solid solution Sr2+xLa1−xGaO5−xFx, the luminescence of Bi3+ is well promoted. Through an excitation-driven strategy, the emission peak position of Bi3+ is redshifted, and the luminescence of trivalent bismuth is successfully adjusted, which can also be applied to anti-blue lighting. In addition, we constructed a Bi3+–Eu3+ dual luminescence system, and, regardless of changes in the Bi3+/Eu3+ concentration or excitation wavelength, a single matrix white light phosphor was realized. Through calculations, the activation energy of the phosphor doped with 2.5%Eu3+ was found to be 0.257 eV, which is higher than the activation energy of some common compounds. This indicates that the phosphor has good application prospects in the field of solid-state lighting. It is worth noting that based on the different thermal response behaviors of Bi3+ and Eu3+, when the Eu3+ content is fixed at 1%, the maximum relative sensitivity of the optical thermometer based on its fluorescence intensity ratio is about 1.46% K−1 at 383 K, which is higher than that of Bi3+ and Eu3+ co-doped phosphors previously reported. We also obtained a high absolute sensitivity of 0.00139 K−1 at 403 K. Therefore, we also studied the thermal sensitivity of Bi3+ and Er3+ co-doped solid solutions. The results show that this solid-solution phosphor has far-reaching application prospects in the temperature sensing field.
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