Controllable synthesis of bifunctional material Ca2Ti2O6:Eu3+ and its comparative study on luminescence and photocatalytic properties with CaTiO3:Eu3+

Pure pyrochlore Ca 2 Ti 2 O 6 , perovskite CaTiO 3 , and their mixed crystalline phases with different proportions were controllably synthesized via a solvothermal method, followed by a subsequent calcination process. RIR (reference intensity ratio) data of Ca 2 Ti 2 O 6 were first obtained by X-ray diffraction (XRD), which can be used to quantitatively analyze the phase composition. When Eu 3+ is doped into these calcium titanium oxides, they can be used as luminescent and photocatalytic materials. The structure, luminescence, and photocatalytic properties of pure pyrochlore Ca 2 Ti 2 O 6 :Eu 3+ and perovskite CaTiO 3 :Eu 3+ were comparatively studied in detail. The relative intensities of the excitation peaks and the emission peaks in Ca 2 Ti 2 O 6 :Eu 3+ and CaTiO 3 :Eu 3+ are different, which is attributed to the different symmetries of Eu 3+ inhabiting the two kinds of lattices. In addition, although the luminescence intensity of CaTiO 3 :3%Eu 3+ is higher than that of Ca 2 Ti 2 O 6 :3%Eu 3+ under excitation at 394 nm, the luminescence intensity of Ca 2 Ti 2 O 6 :3%Eu 3+ is superior to that of CaTiO 3 :3%Eu 3+ under excitation at 464 nm and 533 nm. Photocatalytic experiments show that Ca 2 Ti 2 O 6 :3%Eu 3+ has better photocatalytic performance than CaTiO 3 :3%Eu 3+ , which is mainly due to its smaller crystallite size, higher specific surface area and pyrochlore structure. In addition, biphase (Ca 2 Ti 2 O 6 –CaTiO 3 ):3%Eu 3+ has the best photocatalytic activity compared with the single phase Ca 2 Ti 2 O 6 :3%Eu 3+ and CaTiO 3 :3%Eu 3+ , owing to the presence of heterojunctions that significantly reduced the band gap. It is anticipated that the discovery of this bifunctional Ca 2 Ti 2 O 6 :Eu 3+ would expand the application of rare earth-doped calcium titanium oxide materials.