Simultaneous effects of synthesis temperature and dopants on MgWO₄ UC phosphors

A sequence of coactivated divalent-metal tungstate Er³⁺/Yb³⁺/Mn⁴⁺: MgWO₄ phosphors 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⁺: MgWO₄ phosphors 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⁺: MgWO₄ phosphors 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 × 10⁻³ K⁻¹ @453 K and ∼10.39 × 10⁻³ K⁻¹ @303 K respectively with an accuracy of ±0.42 K@303 K.