Synthesis and luminescence properties of Mn 3+ , Bi 3+ co-doped Y 6 WO 12 for blue phosphor

Mn3+ and Bi3+ co-doped Y6WO12 samples with hexagonal structure were synthesized via an improved salt pyrogenation method at a temperature region of 700–1100 °C for 3 h. In Y6WO12, Mn3+, substituting Y3+, occupies a seven-coordination site and its energy levels are treated in near Oh symmetry. The samples doped by Mn3+ alone emit the most intensive blue light at 420 nm under excitation at 247 nm due to charge transition (CT). The mechanism of sensitization of Bi3+ for Y6WO12:Mn3+ was also analyzed by taking account of metal-to-metal charge-transfer (MMCT) from Bi3+ to Mn3+. As a consequence, the phosphor Y6WO12:Mn3+/Bi3+ can emit blue light under radiation of 370 nm, and the emission intensity is enhanced about five times by the sensitizer Bi3+. The optimal doping concentration of Bi3+ is determined as 1 at% for the emission at 420 nm in Y6WO12:0.5 at% Mn3+ phosphors.