evaporator. The volume of nanoparticle dispersion was chosen such that the final composite would be of a FATO NPs:La0.9Ba0.1F2.9: La2(Ni/Co)O4 1:2:1 weight ratio. After removing the dispersants, the composite was further dried at 170 °C in vacuum for 15 h before being stored in a glovebox. Composites of FATO nanoparticles with exclusively La0.9Ba0.1F2.9 were prepared by the same method, using as-synthesized La0.9Ba0.1F2.9 instead of the mixture of La0.9Ba0.1F2.9