The influence of the presence of barium carbonate (BaCO3) phase on the luminescence properties of barium titanate nanocrystals (BaTiO 3) powders was investigated. Structural and optical characterizations of erbium (Er3+) doped BaTiO3 synthesized by the sol-emulsion-gel were performed. Using Fourier transform infrared spectroscopy and X-ray powder diffraction, we identified the presence of impurities related to BaCO3 and quantified its fraction. It was observed that the presence of BaCO3 phase, even at low levels, depletes significantly the infrared-to-visible upconverted luminescence efficiency of the produced nanopowders. © 2014 G. D. Webler et al.