Luminescence processes in A3IILaNb3O12 (AII = Ba, Sr) layered perovskites

• A3IILaNb3O12 (AII = Sr, Ba) layered perovskites synthesized by co-precipitation.
• Deformation rates calculated for inner and external MeO6 octahedrons.
• Two emission bands assigned to differently deformed NbO6 groups.
• Energy schemes of perfect and deformed NbO6 are considered.

The A3IILaNb3O12 (AII = Sr, Ba) layered perovskites were synthesized by co-precipitation method. Luminescence properties of these compositions have been investigated for the first time. Emission spectra consist of wide bands with maxima located near 430 and 500 nm. Luminescence processes are discussed in connection with features of cation compositions, crystal structure and distortions of the NbO67- groups’ symmetry. Possible scheme of electron states and the lowest allowed electron transitions has been built for the niobate groups of Oh and C3v symmetry. In this scheme, the 430 and 500 nm emission bands were assigned to T1 → A1 and E → A1 electron transitions in the perfect and distorted NbO67- oxyanions, respectively.

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