In this study we report the inclusion of CoFe2O4 as core for Gd2O3:Eu. The introduction of CoFe2O4 didn't change any of the physical properties of Gd2O3:Eu, since the total amount of CoFe2O4 is around 0.2% of the total mass. Nevertheless, it decreased the amount of time needed to achieve a complete crystallographic phase transformation from cubic to monoclinic. Pristine Gd2O3:Eu calcinated at 1,400 degrees C for 1 h barely show the peaks of the monoclinic phase, but with the core it just took 5 min to completely change its crystal structure. We monitor two important physical properties of Gd2O3:Eu, fluorescence and luminescence, neither of both properties suffered any change derive from the inclusion of the core particles, clearly indicating that the only roll of the core particles was to facilitate this structural phase transformation. (C) 2020 Elsevier B.V. All rights reserved.