Simultaneous effects of synthesis temperature and dopants on MgWO4UC phosphors.

A sequence of coactivated divalent-metal tungstate Er3+/Yb3+/Mn4+: MgWO4phosphors have been successfully developed to study the effect of synthesis temperature on the crystal structure, surface morphology, fluorescence, temperature sensing and the dynamics involved in the processes. Upconversion (UC) intensity of the Er3+/Yb3+: MgWO4phosphors increased by ∼109 and ∼778 times on increasing the synthesis temperature from 800 °C to 1000 °C and 1200 °C. UC intensity of the Er3+/Yb3+/Mn4+: MgWO4phosphors has been significantly improved up to ∼90 times via charge compensation. The incorporation of Mn4+in the Er3+/Yb3+codoped crystal system shifted the UC spectra from sharp green peaks to broadband emission along with amended sensing abilities. The ratiometric techniques of thermally coupled stark sublevels of the Er3+have been used to achieve a wide temperature range (300-623 K). The prepared nanophosphors show maximum absolute & relative sensitivities ∼25.86 × 10-3K-1@453 K and ∼10.39 × 10-3K-1@303 K respectively with an accuracy of ±0.42 K@303 K.