Radiative Properties of Up-Conversion Coatings Formed on the Basis of Erbium-Doped Barium Titanate Xerogels

The Stokes and anti-Stokes luminescence of erbium in sol–gel-derived barium-titanate xerogels (BaTiO 3 :Er) and BaTiO 3 /SiO 2 multilayer structures based on these xerogels formed on silicon substrates is studied. It is shown that the up-conversion of erbium in barium-titanate xerogels obtained from erbium nitrate or acetate is observed at an erbium concentration of >3 at %. The up-conversion of erbium is observed at an excitation wavelength of ~980 nm and characterized by an intense band in the 520–560 nm range, corresponding to the 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 radiative transitions of the erbium ion, as well as the bands in the regions of 650 and 850 nm associated with the 4 F 9/2 → 4 I 15/2 and 4 I 9/2 → 4 I 15/2 transitions, respectively. Based on the obtained BaTiO 3 :Er xerogels, multilayer BaTiO 3 :Er/SiO 2 /Si structures are formed on silicon substrates, providing a significant, compared to single-layer BaTiO 3 :Er/Si structures, increase in the intensity of erbium luminescence at the wavelength of the main radiative transition (1540 nm). The prospects of developing up-conversion coatings based on erbium-doped barium titanate for practical applications are discussed.