Enhanced photoluminescence from CaMoO4:Eu3+ by Bi3+ co-doping

When optical active ions are doped into a host, two different methods for determining the composition ratio are usually employed. In one method, the condition for the number of cations was satisfied, in the other method, the condition for the amount of cation charge was satisfied. Until now the two different methods have been adapted, although the local sites of the dopant ions in the host are well known. By comparing the luminescence properties of samples synthesized with different compositions, we observed that the condition for the amount of cation charge (charge compensation) played a key role in the preparation of phosphor materials by enhancing both their crystallinity and covalency. These results demonstrate that the charge compensation is significantly effective in enhancing the emission intensity of the phosphor. Also, when Bi3+ ions are incorporated into the CaMoO4:Eu3+ phosphor, they break the symmetry of the crystal field around the Eu3+ ions and result in an enhancement of the PL intensity by a factors of 1.7 ∼ 2.7 (condition for the number of cations) and 6.2 (condition of charge compensation).