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

The crystal structure and photoluminescence (PL) properties of Tb3+- activated garnet-type Li 7 Li7La3-xZr2O12 garnet phosphors are reported. As - synthesized Li7La3-xZr2O12:xTb (0.02 <= x <= 0.10) phosphors form a tet- ragonal crystal structure and emit efficient green light due to the D-5(4) -> F-7(5) 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.