Blue and red up-conversion light emission in TM-doped A2B2O7 oxides

The crystal structure and light emission property of Yb/Tm doped gadolinium titanate and gadolinium zirconate with chemical composition of A2B2O7 were studied by x-ray diffraction (XRD) and optical spectroscopy measurements, respectively. XRD results suggest that the rare earth titanates have an ordered pyrochlore structure and a defect-fluorite structure for the zirconates. Photoluminescence activated with 1064 nm infrared laser light shows different light emission behaviors for the titanate and zirconate samples, which is related to the different site occupancy of Tm3+ in the lattice of the samples. Only a weak near-infrared (NIR) (∼800 nm) light emission was observed in the titanate samples while a strong blue and red up-conversion emission was detected in the Tm3+-doped zirconate samples. The strong blue and red emission is due to the 7-fold coordinated Tm3+ in the structure.