Enhancement of upconversion emission and temperature sensing of paramagnetic Gd2Mo3O9: Er3+/Yb3+ phosphor via Li+/Mg2+ co-doping

Highlights: • Emission intensity of green and red bands increases via Li⁺/Mg²⁺ ions codoping. • The maximum relative thermal sensitivity of 1.2% K⁻¹ at 300 K was achieved. • The effect of Li⁺/Mg²⁺ ions on the magnetization of the sample was investigated. • The present material is suitable for high temperature sensing and display devices. Herein, enhancement of upconversion emission and temperature sensing in Li⁺/Mg²⁺ co-doped Gd₂Mo₃O₉: Er³⁺/Yb³⁺ is reported. The upconversion emission enhancement of 53 and 21 times is observed in green (524 nm) and red (660 nm) emission bands via simultaneous co-doping of Li⁺/Mg²⁺ ions and is explained in terms of radiative and non-radiative transition rates. High thermal sensitivity of the material is realized upon Li⁺/Mg²⁺ co-doping by measuring the fluorescence intensity ratio of two thermally coupled energy levels (²H_11/2 & ⁴S_3/2) of Er³⁺ ion. The maximum absolute sensitivity of 0.0230 K⁻¹ at 513 K is found for present material and is among the highest measured sensitivities for luminescence based thermometers. Additionally, improved magnetization and magnetic mass susceptibility is also observed on co-doping of Li⁺/Mg²⁺ in the material. The result suggests that simultaneous incorporation of Li⁺/Mg²⁺ is an effective approach for enhancing multifunctionality of Gd₂Mo₃O₉: Er³⁺/Yb³⁺ phosphor and this material has potential applications in colour displays, high temperature sensing and magnetic resonance imaging.