Tunable red-green upconversion luminescence in novel transparent glass ceramics containing Er:: NaYF4 nanocrystals

To develop NaYF4 as bulk luminescence material, transparent glass ceramics containing Er3+: NaYF4 nanocrystals were fabricated for the first time, and the influences of heat-treatment temperature and Er3+ doping level on their upconversion luminescence were investigated. With increasing heating temperature, the upconversion intensity enhanced accordingly, attributing to the incorporation of more Er3+ into the grown NaYF4. Notably, when the heating temperature reached 650 degrees C, the upconversion intensity augmented drastically due to the occurrence of phase transition from the cubic NaYF4 to the hexagonal one. Interestingly, for the samples heat-treated at 620 degrees C, when the Er3+ doping level was increased from 0.05 to 2.0 mol %, the upconversion emission was whole-range tunable from monochromatic green to approximately monochromatic red, which could be mainly attributed to the cross-relaxation between Er3+ ions. The excellent optical properties and its convenient, low-cost synthesis of the present glass ceramic imply that it is an excellent substitution material for the unobtainable bulk NaYF4 crystal, potentially applicable in many fields.