Enhanced Yellow Luminescence from LaAlO3:Sm3+ [Li+, Na+, K+, Ag+] Nano-Phosphors Prepared by Combustion Synthesis

LaAlO3Sm3+, [Li+, Na+, K+, Ag+] nano-phosphors with varying dopant concentrations of Sm3+ from 1 to 20 mol %& codopants concentration of [Li+, Na+, K+, Ag+] is 0.5 to 1 mol % were prepared by combustion synthesis method and the samples were further heated to 600, 700, and 1000 0C to improve the crystallinity of the materials. The structure and morphology of materials have been examined by X-ray diffraction and scanning electron microscopy. XRD results reveal that the sample begins to crystallize at 600C, and pure LaAlO3 phase can be obtained at 700C. SEM images indicate that the Sm3+ -doped LaAlO3 phosphors are composed of aggregated spherical particles with sizes ranging from 40 to 80nm. Under the excitation of UV light (245nm) and low-voltage electron beams (13kV), the Sm3+ -doped LaAlO3 phosphors show the characteristic emissions of phosphor consist of five emission peaks, which are attributed to the transitions from 4G5/2 state to 6HJ (J=5/2, 7/2, 9/2, 11/2, 13/2) states of Sm3+ ions with Yellow, Yellow-orange and Orange-red color. Among these, emission peak located at 563, 598, 611, 653, 707 nm are attributed to the transitions of 4G5/26H5/2, 4G5/26H7/2, 4G5/26H9/2, 4G5/26H11/2& 4G5/26H13/2 respectively. Among these emission peaks, the transition emission 4G5/26HJ (J=5/2, 7/2, 9/2) for peak at 563, 598, 611nm is strongest for Yellow, Yellow-orange and strong Orange-red emission is due to the magnetic dipole transition of Sm3+ ion having a magnetic dipole (MD) allowed one and also an electric dipole (ED) dominated one but the other weak transition 4G5/26H11/2& 4G5/26H13/2 (653nm, 707nm red) is purely an ED one. Highest photoluminescence intensity is observed with 3 mol % doping of (Sm3++ Na+=3mol % for promising Yellow) (Sm3++ K+=3mol %, for Yellow-orangish, Orangish-red), made LaAlO3Sm3+, [Li+, Na+, K+, Ag+] a strong competitor for promising Yellow, Yellow-orange& also for Orange-red colored display applications.