Microstructural origin of peculiar spectra and excellent luminescence properties of Y10Ta4O25:Eu3+ with a fluorite-related structure

Abstract

Inorganic compounds with fluorite-related structures are among the well-known multifunctional materials. In this work, Y₁₀Ta₄O₂₅:Eu³⁺ with a fluorite-related structure was prepared using the ceramic synthesis method. XRD patterns and Rietveld refinements were used to verify the phase formation with an orthorhombic space group of Cmmm (65). The relationship between the luminescence properties and structural characteristics was studied in detail. Compared with earlier reported phosphors, Y₁₀Ta₄O₂₅:Eu³⁺ exhibits peculiar luminescence characteristics. The transition peaks from ⁵D₀ to ⁷F₁, ⁷F₂, and ⁷F₄ (570–720 nm) all showed fairly strong intensities, and emission transitions from the high excited states ⁵D_1,2,3 were detected at room temperature, etc. The experiments confirmed that the peculiar luminescence of Y₁₀Ta₄O₂₅:Eu³⁺ is due to its distinctive structure, such as the strong covalent nature and high polarizability of the (Y/Eu)O₈ polyhedron in the lattice. The doping mechanism was investigated using the spectroscopy probe of Eu³⁺ by laser site-selective excitation and emission in the ⁵D₀ → ⁷F₀ region. Eu³⁺ ions mostly tend to preferentially occupy the Y1 sites first, which show shorter bond lengths and significant electronic repulsion in the (Y/Eu)O₈ polyhedron. The phosphor exhibited a high quantum efficiency of 45% and good thermal stability. Some light-emitting diode lighting devices were fabricated by encapsulating the phosphors and near-UV chip together with resin, and the structures showed a bright reddish-orange color. The photoluminescence characteristics indicated that the Y₁₀Ta₄O₂₅:Eu³⁺ phosphor is promising for LEDs. The results are helpful in developing new reddish-orange emitting materials by introducing Eu³⁺ as a structural probe for doping sites and microstructures.