Variable Photoluminescence Intensity Ratio with the Excitation Wavelength in Eu³⁺-Doped Perovskite-Type Alkaline Earth Zirconates─Possibility of a Unique Visualization of Ultraviolet Light

Abstract

Photoluminescence (PL) spectra arising from 4f−4f dipole transitions of Eu 3+ doped at both the A and B sites of perovskite-type alkaline earth zirconates obtained at various excitation wavelengths were evaluated. Changes in the excitation wavelength caused obvious differences in the PL intensity ratio of the induced electric dipole (ED) 5 D 0 → 7 F 2 transition to the magnetic dipole (MD) 5 D 0 → 7 F 1 transition for Eu 3+ -doped SrZrO 3 and CaZrO 3 , in which only the B site had a center of symmetry. Two charge transfer (CT) bands associated with the excitation of Eu 3+ were observed in the spectra of these oxide samples, which arose from the difference in the electronic structure of the Eu−O coordination at the A and B sites. We conclude that simultaneous Eu 3+ substitution at sites with and without a center of symmetry, which have different charge transfer energies, induced the observed novel PL changes with a changing excitation wavelength. Our results may enable the development of a new type of ultraviolet light detector.

Host-to-Activator Energy Transfer Developed by Eu3+ Doping at B Sites in Perovskite-Type Strontium Stannate Phosphor

“…On the other hand, it is also known that SSO can become phosphors by doping and Ln 3+ ions are frequently doped into the host lattice (HL) as emission centers. − Ln 3+ -doped SSO (SSO:Ln 3+ ) shows some luminescence colors dependent on the Ln 3+ species and the luminescence properties of, especially, SSO:Eu 3+ have been examined widely. However, the intensities of Eu 3+ luminescence in single-doped SSO:Eu 3+ samples are usually small and the shapes of photoluminescence (PL) spectra are controversial although they all show red PL. − The contentious situation is similarly seen in Eu 3+ single-doped SrZrO 3 (SZO) and SrHfO 3 (SHO) samples. − The shape differences in the PL spectra are attributed to the different locations of Eu 3+ ions because Eu 3+ luminescence, which is often obtained by the excitation of charge transfer (CT) bands, is sensitive to the symmetry of the Eu 3+ sites. − In contrast to SZO:Eu 3+ and SHO:Eu 3+ , luminescence by energy transfer (ET) from the HL to Eu 3+ must be taken into account additionally in SSO:Eu 3+ . This is because the bandgap of SSO is not as large as that of SZO and SHO, resulting in the HL absorption being observed in the same wavelength region for the CT excitation.…”