Novel class of aeschynite structure LaNbTiO6-based orange-red phosphors via a modified combustion approach

A novel class of orange-red phosphors based on Eu(3+)-activated LaNbTiO(6) was successfully fabricated by a wet chemical method, called a modified combustion approach. XRD, TG-DTA, SEM, and EDS results show that the heat-treatment of the powders above 1000 degrees C is enough to obtain highly crystallized and phase-pure LaNbTiO(6) and Eu(3+)-doped samples, which is of prime importance in investigating the optical properties of the novel phosphors using LaNbTiO(6) as the host material. UV-vis diffuse reflectance spectroscopy reveals that the direct band gap of LaNbTiO(6) with large grains (above 200 nm) is calculated to be 3.27 eV, while the absorption edge of the small particles shows an obvious blue-shift. Two blue emission bands centered at 440 and 470 nm ascribed to the self-trapped exciton emission of the distorted NbO(6) and TiO(6) groups for the pure LaNbTiO(6) can be obtained. Photoluminescence spectra of the Eu(3+)-doped phosphor particles illuminated the simultaneous occurrence of several intense orange-red band emissions due to the characteristic transitions of (5)D(0,1) --> (7)F(J) (J = 0, 1, 2, 3, 4) of Eu(3+) under 395 nm excitation. The mechanism of these multiplets possibly arising from the odd-parity distortions of the Eu(3+) ion environment and the effect of crystallanity of the compounds on luminescence were discussed, respectively. The highly bright and color-uniform fluorescence images of the doped samples with short luminescence decay times (nanosecond magnitude) confirmed the potential applications of the phosphors in luminescence and display devices.