Effect of temperature on the luminescence and decay behavior of divalent europium in lithium barium borate.

The optical properties of LiBaBO₃ doped with Eu²⁺ are investigated in the temperature regime between 10 and 525 K for the first time. At room temperature (RT), a broad emission band peaking around 485 nm is observed. The emission is ascribed to the 4f⁶5d¹ → 4f⁷ transition on Eu²⁺. The excitation spectra consist of broad bands between 220 and 450 nm. The emission intensity shows no remarkable decline at lower temperatures; although it decreases drastically at higher temperatures. The Stokes shift is calculated to be 0.52 eV. The thermal activation of an electron from the Eu²⁺ excited state to the conduction band is responsible for the thermal quenching behavior in LiBaBO₃:Eu system. The energy gap E_A for the best fit of decay time is 0.38 eV. [ABSTRACT FROM AUTHOR]