Structure-Dopant Concentration Relations in Europium-Doped Yttrium Molybdate and Peak-Sharpening for Luminescence...

A set of Eu³⁺-doped molybdates, Y_2-xEuxMo₃O₁₂ (x = 0.04; 0.16; 0.2; 0.4; 0.8; 1; 1.6; 2), was synthesized using a solid-state technique and their properties studied as a function of Eu³⁺ concentration. X-ray diffraction showed that the replacement of Y³⁺ with larger Eu³⁺ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu₂Mo₃O₁₂. The intensity of typical Eu³⁺ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y₂Mo₃O₁₂:80mol% Eu³⁺. Further, the complete substitution of Y³⁺ with Eu³⁺ in the case of monoclinic Eu₂Mo₃O₁₂ leads to decreased emission intensity. Lifetime follows a similar trend; it is lower in the orthorhombic structure, reaching slightly higher values for the tetragonal structure and showing a strong decrease for monoclinic Eu₂Mo₃O₁₂. Temperature-sensing properties of the sample with the highest red Eu³⁺ emission, Y₂Mo₃O₁₂:80mol% Eu³⁺, were analyzed by the luminescence intensity ratio method. For the first time, the peak-sharpening algorithm was employed to separate overlapping peaks in luminescence thermometry, in contrast to the peak deconvolution method. The Sr (relative sensitivity) value of 2.8 % K^-1 was obtained at room temperature.