Emission spectra from the ⁵D₁ excited state of the compounds containing Eu³⁺

Excitation, photoluminescence, and time-resolved emission spectra of the Eu³⁺-containing compounds, Y_xEu_2-x(CHDC)₃, Eu(NO₃)₃·5H₂O, and Eu₂O₃ were obtained. The coordination polymers, R₂(C₈H₁₀O₄)₃, (R = Eu or Y), were synthesized by mid-temperature hydrothermal technique with the 1,4-cyclohexanedicarboxylate (C₈H₁₀O₄, CHDC) ligands. Blue-shift emission signals were observed in the emission spectra of these Eu³⁺-containing compounds at 561 nm excitation. Power dependence and temperature dependence experiments indicate the blue-shift emission results from one-photon hot band transition to the ⁵D₁ excited state. The Eu^{3+ 5}D₁→⁷F_J emission decay curves and ⁵D₀→⁷F_J emission rising curves of these compounds were acquired. The ⁵D₁ state emission lifetimes are quite different in these compounds and are correlated with the ⁵D₁ → ⁵D₀ relaxation rates. Our analysis shows two possible (Eu³⁺-Eu³⁺ and Eu³⁺-CHDC) cross-relaxation processes that relax ⁵D₁ to ⁵D₀ with different rates in these compounds.