Exploring the Impact of Structure-Sensitivity Factors on Thermographic Properties of Dy 3+ -Doped Oxide Crystals.

Optical absorption spectra and luminescence spectra were recorded as a function of temperature between 295 K and 800 K for single crystal samples of Gd₂SiO₅:Dy³⁺, Lu₂SiO₅:Dy³⁺, LiNbO₃:Dy³⁺, and Gd₃Ga₃Al₂O₁₂:Dy³⁺ fabricated by the Czochralski method and of YAl₃(BO₃)₄:Dy³⁺ fabricated by the top-seeded high temperature solution method. A thermally induced change of fluorescence intensity ratio (FIR) between the ⁴I_15/2→ ⁶H_15/2 and ⁴F_9/2 → ⁶H_15/2 emission bands of Dy³⁺ was inferred from experimental data. It was found that relative thermal sensitivities S_R at 350 K are higher for YAl₃(BO₃)₄:Dy³⁺ and Lu₂SiO₅:Dy³⁺than those for the remaining systems studied. Based on detailed examination of the structural peculiarities of the crystals it was ascertained that the observed difference between thermosensitive features cannot be attributed directly to the dissimilarity of structural factors consisting of the geometry and symmetry of Dy³⁺ sites, the number of non-equivalent Dy³⁺ sites, and the host anisotropy. Instead, it was found that a meaningful correlation between relative thermal sensitivity S_R and rates of radiative transitions of Dy³⁺ inferred from the Judd–Ofelt treatment exists. It was concluded that generalization based on the Judd–Ofelt parameters and luminescence branching ratio analysis may be useful during a preliminary assessment of thermosensitive properties of new phosphor materials. [ABSTRACT FROM AUTHOR]