Enhanced upconversion luminescence of GdVO(4):Er(3+)/Yb(3+) prepared by spray pyrolysis using organic additives

Spray pyrolysis was applied to prepare Er(3+)/Yb(3+)-doped GdVO(4) particles, and their emission properties were investigated by varying the Er(3+)/Yb(3+) content and the calcination temperature from 900 to 1400 °C. Ethylene glycol (EG), citric acid (CA) and N,N-dimethylformamide (DMF) were used as organic additives in order to improve the upconversion of GdVO(4):Er(3+)/Yb(3+). The resulting GdVO(4):Er(3+)/Yb(3+) particles show strong green emission due to (2)H(11/2)/(4)S(3/2) → (4)I(15/2) transitions of Er(3+) and weak red peak due to the (4)F(9/2) → (4)I(15/2) transition of Er(3+). From the result observed by changing the pumping power of the near-infrared (NIR, 980 nm) laser, the observed green emission is caused by a typical two-photon process. In terms of achieving the highest upconversion luminescence, the optimal Er(3+) and Yb(3+) contents are 1.5% and 20% with respect to Gd, respectively. The luminescence intensity steadily increased as the calcination temperature was elevated up to 1200 °C due to the increment of crystallinity. The upconversion intensity showed a linear relationship with the crystallite size in all the calcination temperature range. Using the EG/CA/DMF mixture as organic additives improves the upconversion emission about 4.3 times higher than when no organic additives are used, due to the enhancement of crystallinity as well as the enlargement of primary particle size.