A vanadate-based white light emitting luminescent material for temperature sensing

Calcium magnesium vanadate-europium vanadate powders with a homogeneous distribution have been prepared by a sol-gel method followed by a sintering process. The as-prepared powders show both broadband emission around 520 nm and sharp peak emission at 617 nm under UV light excitation, which are ascribed to the one-electron charge transfer transition in the VO₄ tetrahedra and the typical ⁵D₀ → ⁷F₂ transition of Eu³⁺. Energy transfer occurs between the vanadate and Eu ions. The emission color of the products can be tuned by controlling the Eu concentration and temperature. White light emission can be obtained at the Eu concentration of 15% and at room temperature. The temperature related luminescence properties have been studied for the sample with 15 mol% Eu. The intensity ratio between the broadband emission (due to VO₄ tetrahedra) and the sharp peak emission (due to Eu³⁺ ions) decreases as the temperature increases in a linear relationship. The relative sensitivity (S _R) of this luminescent temperature sensor has been calculated and a maximum has been gained at 455 K with the value equal to 1.83% K^-1.