Enhancement emission intensity of CaMoO4 : Eu3+, Na+ phosphor via Bi co-doping and Si substitution for application to white LEDs

Through the use of Bi as a co-activator and Si as a substituting element for the host lattice, red emitting Ca0.5MoO4 : Eu-0.25-x(3+), Bi-x(3+), Na-0.25(+) (x = 0, 0.005, 0.01, 0.05, 0.10, 0.15 and 0.20) and Ca0.5Mo1-ySiyO4 : Eu-0.25(3+), Na-0.25(+) (y = 0.005, 0.01, 0.02, 0.03, 0.04 and 0.05) phosphors were synthesized by the conventional solid state reaction method, respectively. The photo-luminescent results show all samples can be excited efficiently by UV (396 nm) and blue (467 nm) light and emit red light at 615 nm with line spectra, which are coupled well with the characteristic emission from UVLED and blue LED, respectively. In the Eu3+-Bi3+ co-doped system, both Eu3+ f-f transition and Bi3+ CT transition absorptions are observed in the excitation spectra, the intensities of the main emission line (D-5(0)-->F-7(2) transition of Eu3+ at 615 nm) are strengthened because of the energy transition from Bi3+ to Eu3+. The introduction of Si4+ ions did not change the position of the peaks but enhanced the emission intensity of Eu3+ under 396 nm excitations. The results showed that the optimal doping concentration of Bi3+ ions and Si4+ ions was 1 mol%, respectively.