Improvement of light emission of Mn-doped Zn2 SiO4 phosphors with sodium.

Mn-doped willemite (Zn2 SiO4 :Mn) green phosphor were synthesized by sol-gel technology. The effect of the addition of sodium, as in the composition Zn((1.92 - X)) Na(X) Mn(0.08) SiO4, on the emission behavior was studied. FT-IR and EPR results revealed that sodium ion is incorporated into the lattice and results in the formation of isolated Mn2+ and Mn-Mn pairs. The maximum emission intensity of the sample under ultraviolet (UV) excitation occurred at the sodium concentration of x = ~0.03. The green emission at about 525 nm is assigned to Mn2+ -Mn2+ pair centres on nearest neighbour Zn sites. The highest intensity of the green emission for x = ~0.03 is well close to the highest concentration of the Mn2+ -Mn2+ pair.