Synthesis and fluorescence properties of Tb₂Te₄O₁₁

A new compound, Tb₂Te₄O₁₁, with monoclinic symmetry was synthesized by the solid-state reaction of TeO₂ and Tb₄O₇ in the temperature range 700-800°C in air. Its lattice parameters were calculated to be a = 12.54 Å, b = 5.124 Å, c = 16.08 Å, and β = 106.08°. On heating at 800°C for a long time, the compound gradually changed its chemical formula to Tb₂Te_4-yO_11-2y (y ≤ 0.25) without any structural changes. Also, solid solutions of (Y_1-xTb_x)₂Te₄O₁₁ were synthesized in the range 0.01 ≤ x ≤ 1.0. When the amount of Tb³⁺ increased, the ⁵D₄ emission became intense, whereas the ⁵D₃ emission was quenched by cross-relaxation. Such fluorescence profiles were examined and discussed to provide an understanding of the energy transfer process with respect to the concentration of Tb³⁺ ion.