Experimental study and thermodynamic analysis are conducted to identify a process window for the preparation of BaTiO3-Ni ferroelectric-ferromagnetic composites. A tiny amount of Ni solutes (< 0.5 mol%) can play a key role in the preparation of the composites. The Ni solute acts as an acceptor that enhances the reduction resistance of BaTiO3. Owing to the presence of Ni acceptors, dense BaTiO3-Ni composites can be prepared by sintering above 1330 degrees C in an atmosphere of 1 Pa oxygen partial pressure.