Development of SrWO4:Ho3+/Yb3+ green phosphor for optical thermometry application.

In recent years, the growth of luminescent materials for optical thermometry applications has gained substantial attention due to their non-invasive and contactless nature. This research article presents the synthesis, characterization, and potential application of SrWO4:Ho3+/Yb3+ phosphors as temperature-sensitive materials. The inspection of the structural properties is done by X-ray diffraction and Raman and FTIR spectroscopy. The X-ray diffraction signifies the single tetragonal phase of the materials without any impurity or secondary phase. Nine Raman active modes are detected in the Raman spectra of pure SrWO4 and 10 Raman active bands are present in the doped samples. The morphology and elemental composition are visualised by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy. The spectral properties of these phosphors are evaluated by down-conversion and up-conversion photoluminescence, signifying their suitability for solid state lighting and optical thermometry in various temperature regimes. The phosphors can generate green and yellow light under blue and near-infrared radiation, respectively. The sensitivity of 3.19 × 10-3 K-1 ensures the promising prospects of SrWO4:Ho3+/Yb3+ phosphors for precise and reliable temperature sensing in diverse fields.

An attempt to enhance the afterglow luminescence of NIR light emitting long persistent phosphor Zn3Ga2Ge2O10:Cr3+ by Pr3+ co-doping.

In this study we have focused on the improvement of luminescence intensity and the long afterglow luminescence of Cr3+ doped Zn3Ga2Ge2O10 long persistent phosphor by adding an appropriate amount of Pr3+ ions in proportion with Ga concentration. We have successfully developed a series of long persistent Zn3Ga(2-x-y)CrxPryGe2O10 (where x = 0, 0.04 and y = 0, 0.01, 0.02, 0.03, 0.04) phosphors by high temperature solid state reaction method. The structural properties of the developed phosphors were characterized by X-ray diffraction method. The diffuse reflectance spectra were recorded at room temperature and it shows three strong absorbance bands at the wavelength of 256, 412 and 570 nm due to the transitions of 4A2g→4T1g (4P), 4A2g→4T1g (4F) and 4A2g→4T2g (4F) of Cr+3 ions which are also confirmed from the photoluminescence (PL) excitation spectra. PL emission analysis revealed that developed phosphors have a strong narrow luminescence around 698 nm and significantly enhanced with the Pr3+ content upto its optimum value (0.02). Afterglow NIR light emission from the developed phosphors was captured by night vision monocular and it is found that the phosphors have long persistent luminescence for more than 24 h. Thermoluminescence (TL) measurement was also carried out for better understanding the kinetic mechanism and luminescence process in these materials. This will enable to calculate the trapping parameters associated with prominent glow peaks.