Spectroscopy and Luminescence Dynamics of Ce3+ and Sm3+ in LiYSiO4

The lithium yttrium silicate series of LiY1-x-Ln(x)SiO(4) 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 Ln(3+) 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.