Alkali Silicates Codoped with NIR-Emitting RE (Nd and Yb) Ions for Thermometry Applications.

In the present study, the synthesis of BaSrSiO co-doped Yb and Nd nanophosphors (NPs) was successfully achieved through the conventional sol-gel method, as confirmed by X-ray diffraction and SEM analysis, verifying the formation of pure NPs. The FTIR and Raman spectra analysis confirm the formation of silicates, as different modes and vibrations of Si-O and Si-O-Si were seen at 800-1000 cm. The energy transfer (ET) mechanism between Nd and Yb ions was seen as the emission spectra showed a rise in intensity of one over another. PLE emission spectra showed transitions at F-F for Yb and from F to (I, I, and I1) for Nd when excited at 785 nm. All the samples record low activation energy, which shows that the rate of reaction will be higher in all the samples, and it will be highest for 1 mol% Nd and 1 mol% Yb. An increasing value of τ was seen with increasing Yb concentration, which confirms the increase in the population of trap centers. The positron annihilation lifetime (PAL) curve showed that 1 mol% Yb and 2 mol Nd have single vacancies or shallower positron traps, whereas 3 mol% Yb and 2 mol% Nd have larger defects like surface oxygen vacancy clusters. The other two samples have balance vacancies, which makes them best for thermometry applications. The fluorescence intensity ratio (FIR) was calculated to get sensitivity for thermometry application. 2.13% K sensitivity achieved at 303-333 K temperature.