Crystal structure and photoluminescence properties of garnet−type as−synthesized and aged Li7La3−xZr2O12:xTb phosphors

Abstract The crystal structure and photoluminescence (PL) properties of Tb3+−activated garnet−type Li7La3−xZr2O12 garnet phosphors are reported. As−synthesized Li7La3−xZr2O12:xTb (0.02 ≤ x ≤ 0.10) phosphors form a tetragonal crystal structure and emit efficient green light due to the 5D4 → 7F5 transition of Tb3+. On the other hand, aged Li7La3−xZr2O12:xTb phosphors form mixed tetragonal and cubic crystal structures and contain a small amount of Li2CO3. The aged LLZO:xTb phosphors are brownish due to the oxidation of Tb3+ to Tb4+. The Tb4+ ions act as quenching sites for Tb3+ green emission owing to their strong absorption in UV–visible region. The aging significantly degrades emission intensities and color quality due to the presence of Tb4+ and Li2CO3.