Mn Luminescence in CaZnMnNa(PO) Solid Solution, 0 ≤ ≤ 1.

The solid solution CaZnMnNa(PO) (0 ≤ ≤ 1.0) was obtained by solid-phase reactions under the control of a reducing atmosphere. It was demonstrated that Mn-doped phosphors can be obtained using activated carbon in a closed chamber, which is a simple and robust method. The crystal structure of CaZnMnNa(PO) corresponds to the non-centrosymmetric β-Ca(PO) type (space group 3), as confirmed by powder X-ray diffraction (PXRD) and optical second-harmonic generation methods. The luminescence spectra in visible area consist of a broad red emission peak centered at 650 nm under 406 nm of excitation. This band is attributed to the T → A electron transition of Mn ions in the β-Ca(PO)-type host. The absence of transitions corresponding to Mn ions confirms the success of the reduction synthesis. The intensity of the Mn emission band in CaZnMnNa(PO) rising linearly with increasing of at 0.05 ≤ ≤ 0.5. However, a negative deviation of the luminescence intensity was observed at = 0.7. This trend is associated with the beginning of a concentration quenching. At higher values, the intensity of luminescence continues to increase but at a slower rate. PXRD analysis of the samples with = 0.2 and = 0.5 showed that Mn and Zn ions replace calcium in the 5 (octahedral) sites in the β-Ca(PO) crystal structure. According to Rietveld refinement, Mn and Zn ions jointly occupy the 5 site, which remains the only one for all manganese atoms within the range of 0.05 ≤ ≤ 0.5. The deviation of the mean interatomic distance (∆) was calculated and the strongest bond length asymmetry, ∆ = 0.393 Å, corresponds to = 1.0. The large average interatomic distances between Mn ions in the neighboring 5 sites are responsible for the lack of concentration quenching of luminescence below = 0.5.