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

Photoluminescence (PL) spectra arising from 4f-4f dipole transitions of Eu³⁺ 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) ⁵D₀ → ⁷F₂ transition to the magnetic dipole (MD) ⁵D₀ → ⁷F₁ transition for Eu³⁺-doped SrZrO₃ and CaZrO₃, in which only the B site had a center of symmetry. Two charge transfer (CT) bands associated with the excitation of Eu³⁺ 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 Eu³⁺ 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.