Luminescent enhancement mechanism of Bi3+ Co-doped CaMoO4:Eu3+ investigated by TEM

Eu3+ and Bi3+ doped calcium molybdate particles were carefully examined by high resolution electron microscopy. Visualization of high atomic-weight dopants inside the relatively lightweight calcium molybdate matrix was enabled with the aid of an off-axis high-angle-annular-dark-field (HAADF) technique. The incorporation behaviors of Eu3+, Bi3+ and Eu3+& Bi3+ dopants in the CaMoO4 host were investigated. We consistently found that, Eu3+ ions were evenly distributed in the CaMoO4 host (no clustering), while Bi3+ ions preferred to take the form of nanosized clusters (∼2 nm). Interestingly, in Eu3+& Bi3+ co-doped sample, a minor amount of Bi3+ promoted the clustering of Eu3+ ions. The clustering of Eu3+ ions might be relevant to an energy transfer process in co-doped phosphors.