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

A set of Eu 3+ -doped molybdates, Y 2- xEuxMo 3 O 12 (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 Eu 3+ concentration. X-ray diffraction showed that the replacement of Y 3+ with larger Eu 3+ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu 2 Mo 3 O 12 . The intensity of typical Eu 3+ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y 2 Mo 3 O 12 :80mol% Eu 3+ . Further, the complete substitution of Y 3+ with Eu 3+ in the case of monoclinic Eu 2 Mo 3 O 12 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 Eu 2 Mo 3 O 12 . Temperature-sensing properties of the sample with the highest red Eu 3+ emission, Y 2 Mo 3 O 12 :80mol% Eu 3+ , 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.