Hydrothermal synthesis and upconversion luminescence of cubic-shaped LiNbO3:Yb3+/Er3+ nanocrystals

We exploited a simple hydrothermal route without adding organic additives or hard templates to synthesize cubic-shaped LiNbO 3 :Yb 3+ /Er 3+ with the size of 400–500 nm. Based on the time-dependent investigation on the crystal structure and morphology, Yb(NO 3 ) 3 and Er(NO 3 ) 3 not only could emit green and red upconversion (UC) emission but also could be used as an etchant to increase dissolution rate of the Nb 2 O 5 raw material in the hydrothermal synthesis route. Without addition of Yb 3+ /Er 3+ ions, LiNbO 3 phase could not be formed at even hydrothermal time of 48 h. The time-dependent Raman spectra showed the Raman peaks of LiNbO 3 were occurred at the reaction time of 48 h, and the impurity Nb 2 O 5 phase was disappeared with lengthening hydrothermal time. After calcining at 1050 °C for 2  h, the new Raman peaks at 440/487/531/552 cm −1 and the disappeared OH – absorption peaks at 3429 and 1628 cm −1 favored to produce the bright UC emissions in LiNbO 3 :Yb 3+ /Er 3+ nanocrystals. The pump power dependence and UC mechanism were studied under 980 nm excitation.