Abstract
Visible and near-infrared (NIR) upconversion luminescence (UCL) emissions originating from the BaY(2)F(8): Yb(3+), Tm(3+) systems were investigated under a laser excitation at 980 nm. The BaY(2)F(8):20 mol% Yb(3+), x mol% Tm(3+) and BaY(2)F(8): y mol% Yb(3+), 0.5 mol% Tm(3+) phosphors showed prominent UCL at 800 and 810 nm. The optimized doping concentrations of Yb(3+) and Tm(3+) in the BaY(2)F(8) host matrix were evaluated, their spectroscopic properties were determined, and studies on their temperature-dependent behaviour were carried out. The temperature-sensing properties were studied by generating the fluorescence intensity ratio (FIR) of the UCL peaks originating from the thermally-coupled energy levels of the Tm(3+) ions. The Stark sublevels of (1)G(4) level of Tm(3+) ions were utilized to estimate the temperature-sensing abilities of the phosphor.