Kahwa, Ishenkumba A.,; Parkes, Charmaine C.; McPherson, Gary L.
Author Affiliation, Ana.
Chemistry; Faculty of Pure and Applied Sciences
Energy transport in photoexcited crystals of K3[Tb(C2O4)3(H2O].2H20: Transfer from Tb3+ to Nd3+ and Eu3+
Physical Review B
Date of Publication
The luminescence decay dynamics of Tb3+(5D4) and Eu(5D0) in triclinicf (P1) crystalline K3[Ln(C2O4)3(H20)].2H20 solids was studied between 10 and and 298 K in order to establish the energy-transport characteristics. The luminescence decay rate of Tb3+ (740 s-1 for Ln=Tb3+) is temperature independent for the pure terbium complex; with introduction of Ln3+ dopants (e.g., Ln=Nd, Eu) faster decay rates which are temperature dependent are obtained. For the Eu3+ dopant, excitation buildup on the Eu3+(5D0) decay curve upon Tb3+ (5D4) excitation confirms that energy transfer from Tb3+ ( 5D4) to Ln3+ is active. The temperature dependence of the energy-transfer process in the K3[Eu0.83Tb0.17(C2O4)3(H20)].2H20 mixed complex is well described by a relatively simple empirical expression based on Boltzmann's statistical dynamics of Eu3+ electronic energy among the 7Fj(J=0,1,2) terms. The limiting Eu3+ -Tb3+ transfer rates are ~5.4x103 and 5.3x104 s-1 at 77 and 298 K, respectively. Energy migration on the terbium sublattice was confirmed by compairing Huber's [Phys. Rev. B 20, 2707 (1979)] trapping functions for K3[Eu0.4Tb0.6(C2O4)3(H20)].2H20 and K3[Eu0.4Tb0.1Gd0.5(C2O4)3(H2O)].2H2O (Gd3+ serving as a scatterer for Tb3+ excitation). Although the structure of the complexes features a one-dimensional zigzag array of Ln3+ ions, energy transport is diffusive and not one dimensional....