## 3 Results
Figure 3a shows the 12 K PL of 0.05 mol Sm\({}^{3+}\)-doped CaMoO\({}_{4}\) phosphors, the significant peaks at about 563, 607, and 646 nm are attributed to the \({}^{4}\)G\({}_{5/2}\)\(\rightarrow\)\({}^{6}\)H\({}_{5/2}\), \({}^{4}\)G\({}_{5/2}\)\(\rightarrow\)\({}^{6}\)H\({}_{7/2}\), and \({}^{4}\)G\({}_{5/2}\)\(\rightarrow\)\({}^{6}\)H\({}_{9/2}\) transitions, respectively [9; 18; 19]. It is known that the two transitions (\({}^{4}\)G\({}_{5/2}\)\(\rightarrow\)\({}^{6}\)H\({}_{5/2}\), \({}_{7/2}\)) contain both electric and magnetic dipole transitions, and the \({}^{4}\)G\({}_{5/2}\)\(\rightarrow\)\({}^{6}\)H\({}_{9/2}\) transition belongs to the electronic dipole transition. Moreover, the most intense emission peak at 646 nm in the red region is sensitive to the variation of the local structure environment of the Sm\({}^{3+}\) ions. On the other hands, the marked PL peaks of 0.05 mol Tb\({}^{3+}\)-doped CaMoO\({}^{4}\) phosphors at 489, 544, 588, and 621 nm shown in Figure 3b correspond to the transitions from \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{6}\), \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{5}\), \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{4}\), and \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{3}\) of Tb\({}^{3+}\) ions, respectively [18]. Two significant peaks from the \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{6}\) transition (blue emission) and \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{5}\) transition (green emission) are related to the electric dipole transition and magnetic dipole transition, respectively [20; 21]. [PERSON] et al. further indicate that the \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{6}\) transition depends on the local environment and on the symmetry of crystal field, whereas the \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{5}\) transition is independent of the crystal field strength [21]. Moreover, the current PL measurements of the RE\({}^{3+}\)-doped CaMoO\({}_{4}\) phosphors showed a complete quenching of the broad band emission from (MoO\({}_{4}\))\({}^{2-}\) complex ions, as observed in undoped-CaMoO  
Figure 2: 12 and 300 K PL spectra of undoped-CaMoO\({}_{4}\) phosphors. phosphors, indicating that the absorbed energy of the host has efficiently transferred to the activators [22]. The controllability of the PL emission lines in the visible range on the dopant concentrations have been carried out. The 12 and 300 K PL experimental measurements of Sm3+/Tb3+ co-doped CaMoO4 phosphors with controlled molar ratio of (a) 0.05:0, (b) 0.025:0.025, (c) 0.01:0.04, (d) 0.005/0.045, and (e) 0:0.05 were performed and the spectra plotted in Figure 4.  
The identification of the spectral features, as observed in Figure 4, can be performed by a careful comparison with the observed features in Figure 3. As have been described earlier, the PL peaks at 563, 607, and 646 nm are due to the transitions of Sm3+ ions (marked as \(\bigstar\)), and the PL peaks at 489 and 544 nm are due to the transitions of Tb3+ ions (marked as \(\bigstar\)). Clearly, the measured data of the co-doped sample as depicted by Figure 4 displayed features that can be correlated to the transitions of either Sm3+ ions or Tb3+ ions. Specifically, the PL spectra of (b)-(d) in Figure 4, which belong to the synthesized Sm3+/Tb3+ co-doped CaMoO4 phosphors, have demonstrated the ability of the mixed samples to emit both red- and green-luminescence. Our PL measurement results for the  
Figure 3: PL spectra of CaMoO4 phosphors doped (**a**) 0.05 mol Sm3+ ions and (**b**) 0.05 mol Tb3+ ions. Sm\({}^{3+}\)/Tb\({}^{3+}\) co-doped CaMoO\({}_{4}\) phosphors also showed tunability of the intensity of the visible emission peaks through varying the molar ratio of the doped Sm\({}^{3+}\)/Tb\({}^{3+}\) ions.