Multi-color persistent luminescence in transparent glass ceramics containing spinel nano-crystals with Mn2+ ions

Transparent inorganic materials showing persistent luminescence can act as cover layer and emergency lighting for security signs in the dark. Herein, we report a Mn2+-activated glass and transparent glass ceramics containing spinel-type Zn1+xGa2−2xGexO4 (0 ≤ x ≤ 1) nano-crystals, which show multi-color persistent luminescence for more than 10 min. The color of persistent luminescence showed a remarkable change from red, to orange, greenish, and green with respect to the increase of annealing temperature. The effect has been explained due to the variation of crystal field strength surrounding the Mn2+ ions.