Novel orange-red-emitting Li2Ba5(WO5)3:Eu3+ phosphor for w-LEDs and non-contact thermometry applications

Novel Eu 3+ -activated orange-red phosphors Li 2 Ba (5− x ) (WO 5 ) 3 :xEu 3+ (LBW:xEu 3+ ) (here, 1 ≤ x ≤ 9, ∆ x = 2, and x is the mol%) were successfully prepared via high-temperature solid-phase reaction. The X-ray diffraction (XRD) patterns were recorded for structural analysis and phase identification of the synthesized phosphors. Morphological analysis was done using scanning electron microscopy (SEM). The optical bandgap value has been measured using diffuse reflectance spectra (DRS). The photoluminescence (PL) emission spectra recorded for the LBW:xEu 3+ phosphors under 322 and 396 nm excitation reveal strong visible orange-red emission at 595 nm corresponding to 5 D 0 → 7 F 1 transition of Eu 3+ ions. The CIE chromaticity coordinates were estimated for all the phosphors and were found to be in the deep orange-red region. The PL decay spectral profiles recorded at 595 nm emission when excited with 322 nm light showed a consistent exponential pattern. The experimental lifetimes were observed to decrease as the concentration of Eu 3+ ions increased. In order to study the luminescence intensity ratio (LIR) of the paired emissions lines of Eu 3+ as a function of temperature, PL measurements were carried out in the temperature range of 298–448 K. With a maximum sensitivity of nearly 1.21% K −1 at 298 K, the synthesized phosphors are relatively more sensitive at low temperatures. The aforementioned results represent that the synthesized LBW:Eu 3+ phosphor samples can be employed in non-contact optical thermometry as well as in w-LED applications.