Spectroscopy and Luminescence Dynamics of Ce3+ and Sm3+ in LiYSiO4
2016
The lithium yttrium silicate series of LiY₁–ₓLnₓSiO₄ exhibits superb chemical and optical properties, and with Ln = Ce³⁺, Sm³⁺, its spectroscopic characteristics and luminescence dynamics are investigated in the present work. Energy transfer and nonradiative relaxation dramatically influence the Ln³⁺ luminescence spectra and decay dynamics, especially in the Ce³⁺–Sm³⁺ codoped phosphors. It is shown that thermal-quenching of the blue Ce³⁺ luminescence is primarily due to thermal ionization in the 5d excited states rather than multiphonon relaxation, whereas cross-relaxation arising from electric dipole–dipole interaction between adjacent Sm³⁺ ions is the leading mechanism that quenches the red Sm³⁺ luminescence. In the codoped systems, Ce³⁺–Sm³⁺ energy transfer in competing with the thermal quenching enhance the emission from Sm³⁺. The combined influences of concentration quenching, thermal ionization, and energy transfer including cross-relaxation on the luminescence intensity of single-center and codoped phosphors are analyzed based on the theories of ion–ion and ion–lattice interactions.
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