Thermally stimulated luminescence and electron paramagnetic resonance studies of Eu³⁺-doped yttrium borate

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on gamma-irradiated europium-doped yttrium borate samples in the temperature range 300–600 K. TSL studies showed the presence of two glow peaks, a relatively weaker one at 390 K and an intense one at around 550 K. Room-temperature EPR spectrum of irradiated samples revealed the formation of two hole trapped radicals, namely, BO₃²⁻ and O₂⁻. Temperature variation studies showed drastic reduction in the EPR signal intensities of these radicals around 390 and 550 K indicating thermal destruction of O₂⁻ and BO₃²⁻ radicals, respectively. The observed TSL emission is caused by the recombination of thermally released holes from O₂⁻ and BO₃²⁻ radical ions with electrons. The energy released in electron-hole recombination process is used for the excitation of Eu³⁺ ion resulting in TSL glow peaks. TSL emission studies confirmed that Eu³⁺ acts as luminescent center for both the peaks.