Effect of Eu/Ca ratio on the crystalline phase, morphology and luminescent properties of Ca2-1.5xEux(MoO4)2 (0 ≤ x ≤ 4/3) ceramics phosphors

Abstract A series of Ca 2-1.5x Eu x (MoO 4 ) 2 (0 ≤ x ≤ 4/3) phosphors have been fabricated by a traditional solid-state reaction. The correlations between the crystal structure, luminescent properties and surface morphologies with the chemical composition of the as-fabricated Ca 2-1.5x Eu x (MoO 4 ) 2 crystals have been investigated in detail. The results show that the Ca 2-1.5x Eu x (MoO 4 ) 2 (0 ≤ x ≤ 1.3) phosphors possess tetragonal phase, whereas the obtained Ca 2-1.5x Eu x (MoO 4 ) 2 (x = 4/3) ( i.e. Eu 2 (MoO 4 ) 3 ) phosphor exhibits monoclinic phase. The morphologies of crystals change gradually from quasi sphericity to tetragonal bipyramid owing to the preferential growth along c -axis induced by Eu 3+ ions. The photoluminescence spectra reveal that the intensities of the characteristic emission and excitation peaks initially increase and then decrease with increasing x, given the maximum at x = 1/3. Our results indicate that the difference in the charge, electronegativity, as well as ionic radius between Ca 2+ ions and Eu 3+ ions lead to the variation of crystal symmetry, crystal phase, surface morphologies and luminescence of the final Ca 2-1.5x Eu x (MoO 4 ) 2 crystals.